Product Guides
AIMS Tap & Die Selection Guide: Hand, Spiral Point, Spiral Flute & Forming
A practical guide to selecting the right tap and die for the thread you're cutting. Covers hand taps (taper, plug, bottoming), spiral point taps for through holes, spiral flute taps for blind holes, thread forming taps for ductile material, machine nut taps, die nuts, button dies and die holders. Includes thread system selection (metric, BSP, BSPT, NPT, UNC, UNF, BSW, BSF), tap drill sizing, brand selection across Sutton Tools and Bordo, and AS/NZS/ISO standards.
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AIMS Drill Bit Selection Guide: Choose by Material, Application & Cost
A practical guide to selecting the right drill bit for the workpiece you're cutting. Covers HSS, cobalt HSS, solid carbide, carbide-tipped, masonry, tile and glass drill bits, plus jobber, stub, step and SDS sub-types. Includes drill point geometry, coatings, brand selection across Sutton Tools, Bordo and P&N, and AS/NZS/ISO standards relevant to Australian industry.
Read moreSheet Metal & Wire Gauge Chart: AWG, SWG, BWG to mm
Complete sheet metal and wire gauge cross-reference — AWG (American Wire Gauge), SWG (British Imperial Standard Wire Gauge), and BWG (Birmingham Wire Gauge) converted to millimetres, with Australian usage notes and selection guidance for fabrication, electrical, and tube wall applications.
Read moreMetric to Imperial Conversion Chart: mm, Inches, Drill # & Gauge Cross-Reference
Master engineering conversion reference — 225 rows covering 0.1mm to 25mm, every standard drill number (#1-#80), letter drill (A-Z), AWG gauge, SWG gauge and common imperial fractions in a single cross-reference table.
Read moreSteel Grades Comparison Chart: Carbon, Alloy & Tool Steels
A complete steel grades comparison covering carbon, alloy and tool steels. Cross-references AU (AS 1442 / AS 1444), US (SAE/AISI) and ISO/EN designation systems with compositions, mechanical properties, and typical applications for each grade.
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Recoil Thread Repair Cross-Reference Guide: 2007 → 2013 → 2023 Part Numbers
Recoil renumbered its entire kit catalogue twice in the last twenty years. In 2013 the suffix on every kit code shifted from 0 to 8. In 2023 every code picked up an RC prefix. If you've ever searched an old purchase order, a printed catalogue, or a service-manual callout and come up empty, this is why. This is the single most comprehensive cross-reference for Recoil kit part numbers anywhere in the Australian market. 277 individual kits mapped across all three catalogue generations (2007 → 2013 → 2023), grouped by thread family, with the matching drill bits, STI taps, inserts, install tools and tang break tools spelled out. Cross-reference data compiled by AIMS Industrial from the Recoil 2007 catalogue, the 2013 Australian Price List, and the 2022/2023 catalogue, then validated against the current AIMS Recoil collection. Quick Reference — How to Use This Guide Three things you need to know before reading the tables. The three generations 2007 Part No. — the original Recoil code as listed in the 2007 catalogue. Mostly 5-digit numeric codes ending in 0 (e.g. 35060 for M6 x 1.0). 2013 Part No. — same kit, but the trailing 0 was switched to an 8 across the Australian Price List (e.g. 35068). Some specialty kits gained a hyphenated sub-code (e.g. 38108-2 for the M10 trade spark plug kit). 2023 Part No. (RC) — the current code. Same number as 2013, with a literal RC prefix added (e.g. RC35068). A handful of kits were also re-organised into "Inc.Drill" variants where the matching HSS drill bit is now packed in the box. What "Status" means Stable — number is unchanged, or only gained the RC prefix. Order with confidence. Renumbered — the number changed beyond a simple prefix addition (usually the 2013 suffix shift from 0 to 8). Cross-reference carefully. POA — Price on Application. Kit still exists but moved to special-order in 2023. Contact AIMS for current pricing and lead times. Obsolete — kit appeared in the 2007 and/or 2013 catalogue but is not listed in 2023. See the Obsolete Kits section below for suggested current alternatives. New 2013 — kit didn't exist before the 2013 catalogue. New 2023 — kit was introduced in the 2023 catalogue. RC prefix logic at a glance Recoil's 2023 numbering follows a consistent family pattern. The first two digits after the RC prefix tell you the thread system: RC Prefix Range Thread System Example RC30xxx BSF (British Standard Fine) + BA RC30068 — 5/16-22 BSF RC31xxx BSP (British Standard Pipe) RC31028 — 1/8-28 BSP RC32xxx BSW (British Standard Whitworth) RC32088 — 1/2-12 BSW RC33xxx UNC (Unified National Coarse) RC33048 — 1/4-20 UNC RC34xxx UNF (Unified National Fine) RC34048 — 1/4-28 UNF RC35xxx Metric Coarse RC35068 — M6 x 1.0 RC36xxx NPT / Special Inch RC36028 — 1/8-27 NPT RC37xxx Metric Medium RC37088 — M8 x 1.0 RC38xxx Metric Extra Fine / Spark Plug RC38148 — M14 x 1.25 Spark Plug Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. Most jobs only touch one or two of these families. Find your section in the tables below and read across. Metric Coarse Thread Kits Cross-Reference (M2 to M45) The bread-and-butter family — covers most automotive, machinery and general engineering applications. Range runs from instrument-scale M2 x 0.4 through to heavy industrial M45 x 4.5. AIMS stocks the M3 to M30 range as in-stock variants of the Recoil Thread Repair Kit — Metric 304 Stainless Steel, with the larger sizes available on order from the Recoil collection. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes M2 x 0.4 35020 35028 RC35028 Renumbered 2007→2013: suffix 0→8; same size M2.2 x 0.45 35010 35018 RC35018 Renumbered — M2.5 x 0.45 35250 35258 RC35258 Renumbered — M3 x 0.5 35030 35038 RC35038 Renumbered — M3.5 x 0.6 35350 35358 RC35358 Renumbered 2023: POA only M4 x 0.7 35040 35048 RC35048 Renumbered — M5 x 0.8 35050 35058 RC35058 Renumbered — M6 x 1.0 35060 35068 RC35068 Renumbered — M7 x 1.0 35070 35078 RC35078 Renumbered — M8 x 1.25 35080 35088 RC35088 Renumbered — M9 x 1.25 35090 35098 RC35098 Renumbered — M10 x 1.5 35100 35108 RC35108 Renumbered — M11 x 1.5 35110 35118 RC35118 Renumbered — M12 x 1.75 35120 35128 RC35128 Renumbered — M13 x 1.75 35130 35138 RC35138 Renumbered — M14 x 2.0 35140 35148 RC35148 Renumbered — M15 x 2.0 35150 35158 RC35158 Renumbered — M16 x 2.0 35160 35168 RC35168 Renumbered — M18 x 2.5 35180 35188 RC35188 Renumbered — M20 x 2.5 35200 35208 RC35208 Renumbered — M22 x 2.5 35220 35220 RC35220 Stable 2007→2013: no change M24 x 3.0 35240 35240 RC35240 Stable — M27 x 3.0 35270 35270 RC35270 Stable — M30 x 3.5 35300 35300 RC35300 Stable — M30 x 3.0 — 35300-3 RC353003 New 2013 3mm pitch variant added 2013; 2023: RC353003 M33 x 3.5 — 35330 RC35330 New 2013 — M36 x 4.0 35360 35360 RC35360 Stable — M39 x 4.0 35390 35390 RC35390 Stable — M42 x 4.5 35420 35420 RC35420 Stable — M42 x 4.0 35420-4 35420-4 RC354204 Renumbered 4mm pitch variant; 2023: RC354204 M45 x 4.5 — 35450 RC35450 New 2013 — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. The most popular metric kit in this range is RC35068 (M6 x 1.0) — the size most commonly stripped on cast aluminium engine and gearbox housings. The RC35004R range kit covers M5, M6, M8, M10 and M12 in a single case if you want broad cover. Step up to RC35005R for M6 through M16. For more on diagnosing and avoiding stripped threads in the first place, see our stripped threads guide. Metric Medium Thread Kits Cross-Reference The "medium" family covers metric threads where the pitch sits between coarse and fine — used heavily in automotive applications and where coarse threads would be too aggressive for the material. M8 x 1.0, M10 x 1.25 and M12 x 1.25 are the common sizes here. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes M8 x 1.0 37080 37088 RC37088 Renumbered — M9 x 1.0 37090 — — Obsolete In 2007; dropped by 2013 M10 x 1.25 37100 37103/37108 RC37103/RC37108 Renumbered Split into two SKUs by 2013 M11 x 1.25 37110 37118 — Obsolete 2007 & 2013; not in 2023 M12 x 1.5 37120 37128 RC37128 Renumbered — M13 x 1.5 — 37138 RC37138 New 2013 — M14 x 1.5 37140 37148 RC37148 Renumbered — M15 x 1.5 37150 37158 RC37158 Renumbered — M16 x 1.5 37160 37168 RC37168 Renumbered — M18 x 2.0 37180 37188 RC37188 Renumbered — M20 x 2.0 37200 37208 RC37208 Renumbered — M22 x 2.0 37220 37220 RC37220 Stable — M24 x 2.0 37240 37240 RC37240 Stable — M27 x 2.0 37270 37270 RC37270 Stable — M30 x 2.0 37300 37300 RC37300 Stable — M33 x 2.0 — 37330 RC37330 New 2013 — M36 x 3.0 37360 37360 RC37360 Stable — M39 x 3.0 37390 37390 RC37390 POA 2023: POA only M42 x 3.0 37420 37420 RC37420 POA 2023: POA only M6 x 0.75 Inc.Drill — — RC37060 New 2023 New in 2023 only M9 x 1.0 Inc.Drill — — RC37098 New 2023 New in 2023 only Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. Metric Extra Fine Thread Kits Cross-Reference Extra fine pitches are common on hydraulic fittings, sensor bosses, and precision adjustments. The M14 x 1.25 spark plug thread sits in this family — see the dedicated Spark Plug section below. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes M10 x 1.0 38101 38108 RC38108 Renumbered 2007 suffix 01→08 M11 x 1.0 38110 38118 RC38118 Renumbered — M12 x 1.25 38121 38128 RC38128 Renumbered — M12 x 1.0 — 38120-1 RC381201 New 2013 1mm pitch variant; 2023: RC381201 M13 x 1.25 38130 38138 RC38138 Renumbered — M14 x 1.25 (multi-insert) 38141 38147 RC38147 Renumbered Multi-insert spark plug sizes M14 x 1.25 38140 38148 RC381481 Renumbered 2023: RC381481 M18 x 1.5 38181 38188 RC381881 Renumbered 2023: RC381881 M18 x 1.5 Inconel 38180 38188-1X RC381881X Renumbered High-temp Inconel; 2023: RC381881X M20 x 1.5 38200 38208 RC38208 Renumbered — M22 x 1.5 38220 38220 RC38220 Stable — M24 x 1.5 38240 38240 RC38240 Stable — M26 x 1.5 — 38260 RC38260 New 2013 — M27 x 1.5 38270 38270 RC38270 Stable — M30 x 1.5 38300 38300 RC38300 Stable — M36 x 1.5 38360 38360 RC38360 Stable — M39 x 2.0 38390 38390 RC38390 POA 2023: POA only M42 x 2.0 38420 38420 RC38420 POA 2023: POA only M8 x 0.75 — — RC38080 New 2023 POA in 2023 M10 x 6.8mm x 1.0 — — RC38102 New 2023 Derailleur / bike spec M11 x 1.0 — — RC38110 New 2023 Additional SKU 2023 M25 x 1.5 — — RC38250 New 2023 — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. Spark Plug & Plug Saver Kits Cross-Reference Stripped spark plug threads in cylinder heads are one of the most common Recoil applications. The thread is almost always M14 x 1.25 on modern petrol engines, with M10 x 1.0 and M12 x 1.25 appearing on smaller engines, motorcycles and outboards. M18 x 1.5 covers older diesel and some marine engines. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes M10 x 1.0 Trade 38100 38108-2 RC381082 Renumbered — M12 x 1.25 Trade 38120 38120-2 RC381202 Renumbered 2023: RC381202 M14 x 1.25 Standard 38140 38140 RC38140 Stable — M14 x 1.25 Trade — 38148-2 RC381482 New 2013 2023: RC381482 M18 x 1.5 Trade 38180 38188 RC38188 Renumbered — Plugsaver M14 x 1.25 — 38148 RC38148 New 2013 — Plugsaver Refill — — RC98147RP New 2023 — Plugsaver Ford Triton — — RC98140T New 2023 Ford-specific kit Expanding Tool — — RC98146 New 2023 — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. AIMS keeps the four most common spark plug kits in stock as part of the Recoil collection: RC381082 (M10 x 1.0), RC381202 (M12 x 1.25), RC38140 (M14 x 1.25 standard), the trade version RC381482, and RC38188 (M18 x 1.5). The RC38148 Plug Saver Kit is the field-repair version — designed for in-vehicle use without removing the cylinder head. Left Hand Thread Kits Cross-Reference Left-hand threads appear on bike crank arms, fan shafts, gas valves, and any application where a clockwise-rotating component would otherwise back the fastener off. Recoil's left-hand kits include LH-specific drill bits and STI taps. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes M6 x 1.0 LH Inc.Drill — 35068LH RC35068LH New 2013 — M8 x 1.25 LH Inc.Drill — 35088LH RC35088LH New 2013 — M10 x 1.5 LH Inc.Drill — 35108LH RC35108LH New 2013 — M12 x 1.75 LH Inc.Drill — 35128LH RC35128LH New 2013 — M10 x 1.25 LH Inc.Drill — — RC37108LH New 2023 — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. For combination bike repairs (left and right crank threads in one kit), AIMS stocks the RC3409620 Bike Crank Range Kit. Pilot Nose Tap Kits & Metric Range Kits Cross-Reference Pilot Nose kits use a longer-shanked STI tap with a guide nose — useful for blind holes and tight-access work where a standard tap would wander. The Range Kits (suffix R) bundle multiple thread sizes into a single case for trade and workshop use. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes M6 x 1.0 Pilot Nose Inc.Drill — 35063 RC35063 New 2013 — M8 x 1.25 Pilot Nose — 35083 RC35083 New 2013 — M10 x 1.5 Pilot Nose — 35103 — Obsolete In 2013; not in 2023 M10 x 1.25 Pilot Nose — 37103 RC37103 New 2013 — M12 x 1.75 Pilot Nose — 35123 RC35123 New 2013 — M9 x 1.25 Brake Caliper Kit — — RC35093S New 2023 Specific to brake caliper repair M14 x 1.5 Sump Plug Kit — — RC37143S New 2023 Sump plug thread repair Sizes Included 2007 Part No. 2013 Part No. 2023 Part No. Status Notes M5x.8, M6x1, M8x1.25, M10x1.5, M12x1.75 35004 35004R RC35004R Renumbered 2007: bare number; 2013+: R suffix M6x1, M8x1.25, M10x1.5, M12x1.75, M16x2 35005 35005R RC35005R Renumbered — V/W range (38008 in 2007) 38008 — — Obsolete 2007 only; not in later catalogues O.P.E. range (38007 in 2007) 38007 38007R — Obsolete 2007 & 2013; dropped by 2023 M/C (motorcycle) range 38006 38006R RC38006R Renumbered — M4,M5,M6,M8,M10 — 35003R RC35003R New 2013 — M3,M4,M5,M6,M8 — — RC35006R New 2023 — M4,M5,M6,M8 Mini — 33007R RC33007R New 2013 — M8x1,M10x1,M10x1.25,M12x1.25,M12x1.5 — 37000R RC37000R New 2013 — M6,M8x1.25,M10x1.5,M12x1.75,M14x2 — 37003R RC37003R New 2013 — M4,M6,M8x1.25,M10x1.5,M12x1.75 — 37004R RC37004R New 2013 — M6–M14 fine — 38006R RC38006R New 2013 — M6,M8,M10 Mini 1.25 (Range Kit) — — RC37002 New 2023 — Metric Fine (various) — — RC37008 New 2023 — M6x1.25,M8x1.25,M10x1.5,M12x1.75,M14x1.25 — — RC33005R New 2023 — M6,M8,M9,M10,M12 x1.5 — — RC35007R New 2023 — M6-M14 Range Inc.Drill — — RC37007R New 2023 — M5,M6,M8,M10,M12 Inc.Drill — — RC37009R New 2023 — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. UNC Thread Kits Cross-Reference (Unified National Coarse) UNC is the standard coarse thread family in the United States and dominant on US-built equipment, agricultural machinery, and a large slice of Australian industrial inventory. Sizes run from instrument-scale #2-56 through to 1 1/2"-6. For more on identifying UNC vs UNF threads on Australian-spec fasteners, see our choosing the right drill and tap guide. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes #2-56 33520 33528 RC33528 Renumbered Inc.Drill in 2023 #3-48 33530 33538 RC33538 Renumbered Inc.Drill in 2023 #4-40 33540 33548 RC33548 Renumbered Inc.Drill in 2023 #5-40 33550 33558 RC33558 Renumbered Inc.Drill in 2023 #6-32 33560 33568 RC33568 Renumbered Inc.Drill in 2023 #8-32 33580 33588 RC33588 Renumbered Inc.Drill in 2023 #10-24 33600 33608 RC33608 Renumbered — #12-24 33620 33628 RC33628 Renumbered — 1/4-20 33040 33048 RC33048 Renumbered — 5/16-18 33050 33058 RC33058 Renumbered — 3/8-16 33060 33068 RC33068 Renumbered — 7/16-14 33070 33078 RC33078 Renumbered — 1/2-13 33080 33088 RC33088 Renumbered — 9/16-12 33090 33098 RC33098 Renumbered — 5/8-11 33100 33108 RC33108 Renumbered — 11/16-11 33110 33110 RC33110 POA 2023: POA only 3/4-10 33120 33128 RC33128 Renumbered — 7/8-9 33140 33140 RC33140 Stable No change 2007→2013 1-8 33160 33160 RC33160 Stable — 1 1/8-7 33180 33180 RC33180 Stable — 1 1/4-7 33200 33200 RC33200 Stable — 1 3/8-6 33220 33220 RC33220 Stable — 1 1/2-6 33240 33240 RC33240 Stable — 1/2-13 LH — 33088LH RC33088LH New 2013 — 1/4-20 LH Inc.Drill — 33048LH RC33048LH New 2013 — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. AIMS stocks the common UNC range as in-stock variants of the Recoil Thread Repair Kit — UNC 304 Stainless Steel. The RC33004R range kit covers 1/4" to 1/2" UNC — the trade workhorse for US-spec automotive, agricultural and industrial work. UNF Thread Kits Cross-Reference (Unified National Fine) UNF (Unified National Fine) shares the same nominal diameters as UNC but with a finer pitch — used where vibration resistance or precise adjustment matters. Common on aerospace, military spec equipment, and high-spec automotive. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes #3-56 34530 34538 RC34538 Renumbered Inc.Drill in 2023 #4-48 34540 34548 RC34548 Renumbered Inc.Drill in 2023 #6-40 34560 34568 RC34568 Renumbered Inc.Drill in 2023 #8-36 34580 34588 RC34588 Renumbered Inc.Drill in 2023 #10-32 34600 34608 RC34608 Renumbered — #12-28 34620 34628 RC34628 Renumbered — 1/4-28 34040 34048 RC34048 Renumbered — 5/16-24 34050 34058 RC34058 Renumbered — 3/8-24 34060 34068 RC34068 Renumbered — 7/16-20 34070 34078 RC34078 Renumbered — 1/2-20 34080 34088 RC34088 Renumbered — 9/16-18 34090 34098 RC34098 Renumbered — 5/8-18 34100 34108 RC34108 Renumbered — 3/4-16 34120 34128 RC34128 Renumbered — 7/8-14 34140 34140 RC34140 Stable — 1-12 34160 34160 RC34160 Stable — 1-14 UNS Special 34160-14 34160-14 RC3416014 Renumbered 2023: RC3416014 1 1/16-12 — — RC34170 New 2023 POA in 2023 1 1/8-12 34180 34180 RC34180 Stable — 1 1/4-12 34200 34200 RC34200 Stable — 1 3/8-12 34220 34220 RC34220 Stable — 1 1/2-12 34240 34240 RC34240 Stable — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. AIMS stocks the popular UNF range under the Recoil Thread Repair Kit — UNF 304 Stainless Steel. The RC34004R range kit covers 1/4" to 1/2" UNF in a single case. UNEF Thread Kits Cross-Reference (Unified National Extra Fine) UNEF is rarer than UNC or UNF and largely absorbed into range kits in the 2023 catalogue. Most of the standalone UNEF kits are now obsolete or POA — see the Obsolete section below. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes 1/4-32 34040-32 34040-32 — Obsolete 2007 & 2013; not in 2023 7/16-24 34070-24 34070-24 — Obsolete 2007 & 2013; not in 2023 9/16-20 34090-20 34090-20 RC3409020 Renumbered 2023: new format RC3409020 1-18 — — RC3416018 New 2023 POA 2023 1-20 — — RC3416020 New 2023 — 7/16-24 Inc.Drill — — RC3407824 New 2023 — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. Special Inch Threads — Harley Davidson, Carburettor, Cummins, UN This is where the 2007 and 2013 catalogues had a long tail of specialty kits — Harley Davidson 1/4-24, carburettor 5/16-24, Cummins fuel injector threads, and UN-series. Many of these were absorbed into range kits in 2023 or moved to POA status. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes 1/4-24 Harley Davidson 34040-24 34040-24 — Obsolete 2007 & 2013; absorbed into range kit RC34008R in 2023 7/16-16 Harley Davidson 34070-16 34070-16 — Obsolete Absorbed into RC34008R 7/8-20 Carburettor 34140-20 34140-20 — Obsolete 2007 & 2013; not in 2023 1-20 Carburettor 34160-20 34160-20 — Obsolete 2007 & 2013; not in 2023 11/16-16 Cummins 34110-16 34110-16 RC3411816 Renumbered 2023: RC3411816 7/8-12 UN Special — — RC3414012 New 2023 — 7/8-2 UN Special — — RC3414020 New 2023 — 1/4-24 UN Inc.Drill — — RC3404824 New 2023 — 7/16 UN Inc.Drill — — RC3407816 New 2023 — 1 1/8-8 UN 36180 36180 RC36180 POA 2023: POA only 1 1/4-8 UN 36200 36200 RC36200 POA 2023: POA only 1 3/8-8 UN 36220 36220 RC36220 POA 2023: POA only 1 1/2-8 UN 36240 36240 RC36240 POA 2023: POA only 1 5/8-8 UN 36260 36260 RC36260 POA 2023: POA only 1 3/4-8 UN 36280 36280 RC36280 POA 2023: POA only 1 7/8-8 UN 36300 36300 RC36300 POA 2023: POA only 2-8 UN 36320 36320 RC36320 POA 2023: POA only Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. BSW Thread Kits Cross-Reference (British Standard Whitworth) Whitworth threads are still common on older British, Australian and Commonwealth-built machinery — particularly vintage automotive, plumbing, and machine tools manufactured before metric conversion in the 1970s. AIMS gets steady demand for BSW repair kits, especially the 1/2-12 BSW size. For a broader walk-through of imperial vs metric thread identification, see our tap and die guide. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes 1/8-40 32020 32028 RC32028 Renumbered — 3/16-24 32030 32038 RC32038 Renumbered — 1/4-20 32040 32048 RC32048 Renumbered — 5/16-18 32050 32058 RC32058 Renumbered — 3/8-16 32060 32068 RC32068 Renumbered — 7/16-14 32070 32078 RC32078 Renumbered — 1/2-12 32080 32088 RC32088 Renumbered — 9/16-12 32090 32098 RC32098 Renumbered — 5/8-11 32100 32108 RC32108 Renumbered — 3/4-10 32120 32128 RC32128 Renumbered — 7/8-9 32140 32140 RC32140 Stable — 1-8 32160 32160 RC32160 Stable — 1 1/8-7 32180 32180 RC32180 POA 2023: POA only 1 1/4-7 32200 32200 RC32200 POA 2023: POA only 1 3/8-6 32220 32220 RC32220 POA 2023: POA only 1 1/2-6 32240 32240 RC32240 POA 2023: POA only Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. AIMS stocks RC32088 (1/2-12 BSW) as a standalone kit, and the broader RC32004R range kit for 1/4" to 1/2" BSW. BSP Thread Kits Cross-Reference (British Standard Pipe) BSP threads are everywhere on Australian plumbing and fluid systems — hose fittings, pump bosses, valve bodies, instrumentation. AIMS stocks the common range as variants of the Recoil Thread Repair Kit BSP 304 Stainless Steel. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes 1/8-28 31020 31028 RC31028 Renumbered — 1/4-19 31040 31048 RC31048 Renumbered — 3/8-19 31060 31068 RC31068 Renumbered — 1/2-14 31080 31080 RC31080 Stable — 5/8-14 31100 31100 RC31100 Stable — 3/4-14 31120 31120 RC31120 Stable — 1-11 31160 31160 RC31160 Stable — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. NPT Thread Kits Cross-Reference (National Pipe Thread Tapered) NPT is the US tapered pipe thread — distinct from BSP and not directly interchangeable. Common on US-built pneumatic and hydraulic equipment. For Allthread, studs and matching thread standards see our threaded rod guide. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes 1/8-27 36020 36028 RC36028 Renumbered — 1/4-18 36040 36048 RC36048 Renumbered — 3/8-18 36060 36068 RC36068 Renumbered — 1/2-14 36080 36080 RC36080 Stable — 3/4-14 36120 36120 RC36120 Stable Note: 2013 listed as 36128 — minor discrepancy 1-11.5 — 36160 — Obsolete In 2013; not in 2023 Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. BSF Thread Kits Cross-Reference (British Standard Fine) BSF — the fine-thread variant of Whitworth. Used on older British motorcycles, vintage automotive applications, and pre-metric machine tools. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes 3/16-32 30030 30038 RC30038 Renumbered — 1/4-26 30040 30048 RC30048 Renumbered — 5/16-22 30050 30058 RC30058 Renumbered — 3/8-20 30060 30068 RC30068 Renumbered — 7/16-18 30070 30078 RC30078 Renumbered — 1/2-16 30080 30080 RC30088 Renumbered 2013 30080→30088 in some listings 9/16-16 30090 30090 RC30098 Renumbered — 5/8-14 30100 30100 RC30108 Renumbered — 3/4-12 30120 30120 RC30128 Renumbered — 7/8-11 30140 30140 RC30140 Stable — 1-10 30160 30160 RC30160 Stable — 1 1/4-9 30200 30200 RC30200 Stable — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. AIMS stocks the RC30004R range kit for 1/4" to 1/2" BSF. BA Thread Kits Cross-Reference (British Association — Fine Instrument Threads) BA threads are used on precision instruments, scientific equipment, electrical terminations and clock movements. Sizes run from 0 BA (largest) down to 8 BA (smallest). Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes 0 BA 30500 30508 RC30508 Renumbered — 2 BA 30520 30528 RC30528 Renumbered — 4 BA 30540 30548 RC30548 Renumbered — 6 BA 30560 30568 RC30568 Renumbered — BA 0–6 Range Kit — — RC30504R New 2023 — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. BSC / Brass Thread Kits Cross-Reference (British Standard Cycle / 26 TPI Brass) BSC (also called the 26 TPI Brass thread family) was Recoil's 2007-only catalogue family covering vintage bicycle, Commonwealth electrical and brass-trade threads. The bulk of this family is now Obsolete in 2023 — special order only. Thread Size 2007 Part No. 2013 Part No. 2023 Part No. (RC) Status Notes 1/4-26 30040 — — Obsolete 2007 only (listed under BSC/Brass); not separate in later cats 5/16-26 36500 36508 RC36508 Renumbered — 3/8-26 36600 36608 RC36608 Renumbered — 7/16-26 36700 36708 RC36708 Renumbered — 1/2-26 36800 36808 RC36808 Renumbered — Sizes Included 2007 Part No. 2013 Part No. 2023 Part No. Status Notes UNC 1/4-20, 5/16-18, 3/8-16, 7/16-14, 1/2-13 33004 33004R RC33004R Renumbered — UNF 1/4-28, 5/16-24, 3/8-24, 7/16-20, 1/2-20 34004 34004R RC34004R Renumbered — BSW 1/4–1/2 32004 32004R RC32004R Renumbered — BSP 1/8, 1/4, 3/8 — 31004R RC31004R New 2013 — BSF 1/4–1/2 30004 30004R RC30004R Renumbered — NPT 1/8, 1/4, 3/8, 1/2 — 36004R RC36004R New 2013 — UNC 1/4, 5/16, 3/8 — 33001R RC33001R New 2013 — UNC 1/4–1/2 — 33004R RC33004R New 2013 2013 duplicate listing UNF 1/4, 5/16, 3/8 — 34001R RC34001R New 2013 — UNC Mini #4,#6,#8,#10-24,#10-32 33002 33002R RC33002R Renumbered — BSC 1/4, 5/16, 3/8, 7/16, 1/2 — 36001R RC36001R New 2013 — 9/16 & M10x6.8 Popular — 34005 RC34005 New 2013 — 1/4-24 Harley, 7/16-16 Harley, 3/8-20 BSF — 34008R RC34008R New 2013 Replaces individual Harley kits BA 0–6 — — RC30504R New 2023 — 5 x 9/16-20 LH & RH Bike Crank — 3409620 RC3409620 Renumbered 2023: RC3409620 9/16 Left Bike Crank — — RC3409820BCL New 2023 — 9/16 Right Bike Crank — — RC3409820BCR New 2023 — M6,M8,M9,M10,M12 x1.5 Popular — — RC35007R New 2023 — VW range (38008 in 2007) 38008 — — Obsolete 2007 only Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. Replacement Parts — Drill Bits, STI Taps, Inserts & Tools Every Recoil kit is a system: an oversize drill bit, an STI (Screw Thread Insert) tap that cuts the larger hole, the inserts themselves, a manual install tool, and a magnetic tang break tool to snap off the insert's installation tang once it's seated. Lose or break any one of these and the rest of the kit becomes useless — except you can buy each part separately from the AIMS Recoil collection. The tables below list, for each current RC kit, the exact replacement parts you need. Drill bits are cross-referenced against Sutton Tools D180 codes — Sutton is the AIMS-preferred HSS drill bit brand, and (relevantly) Sutton Tools is Recoil's parent company, so the drill cross-references are first-party data. For a wider view of drill bit sizing across metric and imperial, see our threading tap metric/imperial size chart. What's an STI tap? STI stands for Screw Thread Insert. An STI tap looks like a standard tap but cuts a slightly larger hole — the size needed to accept the Recoil insert. You can't substitute a standard tap. Recoil's STI taps are sold in three styles: Taper (long lead-in, for through-holes), Intermediate (medium lead, the general-purpose choice listed in the tables below), and Bottoming (short lead, for blind holes where you need threads right to the bottom). AIMS stocks all three styles — see Metric Intermediate, Metric Bottoming, and the matching UNC Taper versions. Metric Coarse Replacement Parts Thread Size Current Kit (RC) HSS Drill Bit STI Tap Inserts (Pack of 10) Install Tool Tang Break Tool M2 x 0.4 RC35028 Included (std HSS)2.2mmSutton D180 0220 RC45025 RC25022, RC25023, RC25024 † RC5006121 RC59060M M2.2 x 0.45 RC35018 Included (std HSS)2.5mmSutton D180 0250 RC45015 RC25013 † RC5006121 RC59060M M2.5 x 0.45 RC35258 Included (std HSS)2.8mmSutton D180 0280 RC45255 RC25253, RC25254 † RC5008917 — M3 x 0.5 RC35038 Included (std HSS)3.3mmSutton D180 0330 RC45035 RC25032, RC25033, RC25034 † RC5008917 RC59090M M3.5 x 0.6 RC35358 — RC45355 RC25353 † RC5009515 — M4 x 0.7 RC35048 Included (std HSS)4.5mmSutton D180 0450 RC45045 RC25042, RC25043, RC25044 † RC5012513 RC59080M M5 x 0.8 RC35058 Included (std HSS)5.5mmSutton D180 0550 RC45055 RC25052, RC25053, RC25054 † RC501569 RC59160M M6 x 1.0 RC35068 Included (std HSS)6.8mmSutton D180 0680 RC45065 RC25062, RC25063, RC25064, RC25065 † RC501885 RC59190M M7 x 1.0 RC35078 Included (std HSS)7.8mmSutton D180 0780 RC45075 RC25072, RC25073, RC25074 † RC502194 RC59200M M8 x 1.25 RC35088 Included (std HSS)8.8mmSutton D180 0880 RC45085 RC25082, RC25083, RC25084, RC25085 † RC502507 RC59250M M9 x 1.25 RC35098 Included (std HSS)9.5mmSutton D180 0950 RC45095 RC25092, RC25093 † RC502815 RC59310M M10 x 1.5 RC35108 Included (std HSS)11.0mmSutton D180 1100 RC45105 RC25102, RC25103, RC25104, RC25105 † RC502814 RC59280M M11 x 1.5 RC35118 Included (std HSS)12.5mmSutton D180 1250 RC45115 RC25112, RC25113 † RC503444 RC59340M M12 x 1.75 RC35128 Not included(>13.0mm — outside D180 range) RC45125 RC25122, RC25123, RC25124 † RC503751 RC59380M M13 x 1.75 RC35138 Not included(>13.0mm — outside D180 range) RC45135 RC25133 † RC503751 — M14 x 2.0 RC35148 — RC45145 RC25142, RC25143, RC25144 † RC504380 — M15 x 2.0 RC35158 — RC45155 RC25153 † RC504380 — M16 x 2.0 RC35168 — RC45165 RC25162, RC25163, RC25164, RC25165 † RC505000 — M18 x 2.5 RC35188 — RC45185 RC25183 † RC505910 — M20 x 2.5 RC35208 — RC45205 RC25203 † RC505910 — M22 x 2.5 RC35220 — RC45225 RC25223 † RC50688 — M24 x 3.0 RC35240 — RC45245 RC25243 † RC50750 — M27 x 3.0 RC35270 — RC45275 RC25243 † RC50875 — M30 x 3.5 RC35300 — RC45305 RC25303 † RC51000 — M30 x 3.0 RC353003 — RC453053 RC25303 † RC51000 — M33 x 3.5 RC35330 — RC45335 RC25303 † RC51063 — M36 x 4.0 RC35360 — RC45365 RC25303 † RC51063 — M39 x 4.0 RC35390 — RC45395 RC25303 † RC51250 — M42 x 4.5 RC35420 — RC45425 RC25303 † RC51250 — M42 x 4.0 RC354204 — RC45425 RC25303 † RC51250 — M45 x 4.5 RC35450 — RC45425 RC25303 † RC51250 — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. Metric Medium & Extra Fine Replacement Parts Thread Size Current Kit (RC) HSS Drill Bit STI Tap Inserts (Pack of 10) Install Tool Tang Break Tool M8 x 1.0 RC37088 Included (std HSS)8.5mmSutton D180 0850 RC47085 RC27082, RC27083, RC27084 † RC502507 RC59250M M12 x 1.5 RC37128 Included (std HSS)13.0mmSutton D180 1300 RC47125 RC27122, RC27123, RC27124 † RC503751 RC59380M M13 x 1.5 RC37138 Not included(>13.0mm — outside D180 range) RC47135 RC27133 † RC503751 — M14 x 1.5 RC37148 — RC47145 RC27142, RC27143, RC27144 † RC504380 — M15 x 1.5 RC37158 — RC47155 RC27153 † RC504380 — M16 x 1.5 RC37168 — RC47165 RC27162, RC27163, RC27164, RC27165 † RC505000 — M18 x 2.0 RC37188 — RC47185 RC27183 † RC505910 — M20 x 2.0 RC37208 — RC47205 RC27203 † RC505910 — M22 x 2.0 RC37220 — RC47225 RC27223 † RC50688 — M24 x 2.0 RC37240 — RC47245 RC27243 † RC50750 — M27 x 2.0 RC37270 — RC47275 RC27243 † RC50875 — M30 x 2.0 RC37300 — RC47305 RC27243 † RC51000 — M33 x 2.0 RC37330 — RC47335 RC27243 † RC51063 — M36 x 3.0 RC37360 — RC47365 RC27243 † RC51063 — M39 x 3.0 RC37390 — RC47395 RC27243 † RC51250 — M42 x 3.0 RC37420 — RC47425 RC27243 † RC51250 — M10 x 1.0 RC38108 Included (std HSS)10.5mmSutton D180 1050 RC48105 RC28102, RC28103 † RC502814 RC59280M M11 x 1.0 RC38118 Included (std HSS)11.5mmSutton D180 1150 RC48115 RC28113 † RC503444 RC59340M M12 x 1.25 RC38128 Included (std HSS)12.8mmSutton D180 1280 RC48125 RC28122, RC28123, RC28124 † RC503751 RC59380M M12 x 1.0 RC381201 Included (std HSS)12.5mmSutton D180 1250 RC481251 RC28122, RC28123 † RC503751 RC59380M M13 x 1.25 RC38138 — RC48135 RC28133 † RC503751 — M14 x 1.25 (multi-insert) RC38147 — RC48145 RC28147 † RC504380 RC59380M M14 x 1.25 RC381481 — RC48145 RC28148, RC28149 † RC504380 RC59380M M18 x 1.5 RC381881 — RC48185 RC28183, RC28189 † RC505910 — M18 x 1.5 Inconel RC381881X — RC48185 RC28183 RC505910 — M20 x 1.5 RC38208 — RC48205 RC28203 † RC505910 — M22 x 1.5 RC38220 — RC48225 RC28223 † RC50688 — M24 x 1.5 RC38240 — RC48245 RC28243 † RC50750 — M26 x 1.5 RC38260 — RC48265 RC28263 † RC50875 — M27 x 1.5 RC38270 — RC48275 RC28263 † RC50875 — M30 x 1.5 RC38300 — RC48305 RC28263 † RC51000 — M36 x 1.5 RC38360 — RC48365 RC28263 † RC51063 — M39 x 2.0 RC38390 — RC48395 RC28263 † RC51250 — M42 x 2.0 RC38420 — RC48425 RC28263 † RC51250 — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. Spark Plug & Left Hand Replacement Parts Thread Size Current Kit (RC) HSS Drill Bit STI Tap Inserts (Pack of 10) Install Tool Tang Break Tool M10 x 1.0 Trade RC381082 — RC48105 RC2814084 RC502814 RC59280M M12 x 1.25 Trade RC381202 — RC48125 RC28140124, RC28140164 RC503751 RC59380M M14 x 1.25 Standard RC38140 — RC48145 RC38140 RC504380 — M14 x 1.25 Trade RC381482 — RC48145 RC28140124, RC28143125 RC504380 RC59380M M18 x 1.5 Trade RC38188 — RC48185 RC28183, RC28189 † RC505910 — Plugsaver M14 x 1.25 RC38148 — RC48145 RC28143125 RC504380 — M6 x 1.0 LH Inc.Drill RC35068LH Included (std HSS)6.8mmSutton D180 0680 RC45065LH RC25063LH † RC501885 RC59190M M8 x 1.25 LH Inc.Drill RC35088LH Included (std HSS)8.8mmSutton D180 0880 RC45085LH RC25083LH † RC502507 RC59250M M10 x 1.5 LH Inc.Drill RC35108LH Included (std HSS)11.0mmSutton D180 1100 RC45105LH RC25103LH † RC502814 RC59280M M12 x 1.75 LH Inc.Drill RC35128LH Not included(>13.0mm — outside D180 range) RC45125LH RC25123LH † RC503751 RC59380M Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. Pilot Nose & Range Kit Replacement Parts Thread Size Current Kit (RC) HSS Drill Bit STI Tap Inserts (Pack of 10) Install Tool Tang Break Tool M6 x 1.0 Pilot Nose Inc.Drill RC35063 Included (std HSS)6.8mmSutton D180 0680 RC45067 RC25062, RC25063 † RC501885 RC59190M M8 x 1.25 Pilot Nose RC35083 Not included RC45087 RC25082, RC25083 † RC502507 RC59250M M10 x 1.25 Pilot Nose RC37103 Included (std HSS)10.5mmSutton D180 1050 RC47105 RC27102, RC27103 † RC502814 RC59280M M12 x 1.75 Pilot Nose RC35123 Not included RC45127 RC25122, RC25123 † RC503751 RC59380M Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. UNC Replacement Parts Thread Size Current Kit (RC) HSS Drill Bit STI Tap Inserts (Pack of 10) Install Tool Tang Break Tool #2-56 RC33528 Included (std HSS)#4 (2.8mm)Sutton D180 0280 RC43525 RC23522, RC23523, RC23524 † RC5006117 RC59060M #3-48 RC33538 Included (std HSS)#5 (3.2mm)Sutton D180 0320 RC43535 RC23533 † RC5006917 RC59070M #4-40 RC33548 Included (std HSS)#6 (3.5mm)Sutton D180 0350 RC43545 RC23542, RC23543, RC23544 † RC5007717 RC59080M #5-40 RC33558 Included (std HSS)#6 (3.5mm)Sutton D180 0350 RC43555 RC23552, RC23553 † RC5008918 RC59080M #6-32 RC33568 Included (std HSS)#8 (4.0mm)Sutton D180 0400 RC43565 RC23562, RC23563, RC23564 † RC5009516 RC59100M #8-32 RC33588 Included (std HSS)#8 (4.0mm)Sutton D180 0400 RC43585 RC23582, RC23583, RC23584 † RC5012514 RC59130M #10-24 RC33608 Included (std HSS)#10 (4.8mm)Sutton D180 0480 RC43605 RC23602, RC23603, RC23604 † RC5014011 RC59140M #12-24 RC33628 Included (std HSS)#11 (4.9mm)Sutton D180 0490 RC43625 RC23622, RC23623 † RC5015610 RC59140M 1/4-20 RC33048 Included (std HSS)17/64" (6.7mm)Sutton D180 0670 RC43045 RC23042, RC23043, RC23044 † RC5018810 RC59190M 5/16-18 RC33058 Included (std HSS)21/64" (8.3mm)Sutton D180 0830 RC43055 RC23052, RC23053, RC23054 † RC502198 RC59220M 3/8-16 RC33068 Included (std HSS)13/32" (10.3mm)Sutton D180 1030 RC43065 RC23062, RC23063, RC23064 † RC502507 RC59250M 7/16-14 RC33078 Included (std HSS)29/64" (11.5mm)Sutton D180 1150 RC43075 RC23072, RC23073 † RC503443 RC59340M 1/2-13 RC33088 Not included(>13.0mm — outside D180 range) RC43085 RC23082, RC23083 † RC503752 RC59380M 9/16-12 RC33098 Not included(>13.0mm — outside D180 range) RC43095 RC23093 † RC504380 RC59380M 5/8-11 RC33108 Not included(>13.0mm — outside D180 range) RC43105 RC23102, RC23103 † RC505000 RC59380M 11/16-11 RC33110 — RC43115 RC23113 † RC505000 — 3/4-10 RC33128 — RC43125 RC23122, RC23123 † RC505000 — 7/8-9 RC33140 — RC43145 RC23143 † RC50688 — 1-8 RC33160 — RC43165 RC23163 † RC50750 — 1 1/8-7 RC33180 — RC43185 RC23182, RC23183 † RC50875 — 1 1/4-7 RC33200 — RC43205 RC23202, RC23203 † RC51000 — 1 3/8-6 RC33220 — RC43225 RC23223 † RC51063 — 1 1/2-6 RC33240 — RC43245 RC23242, RC23243 † RC51063 — 1/2-13 LH RC33088LH Not included(>13.0mm — outside D180 range) RC43085 RC23082, RC23083 † RC503752 RC59380M 1/4-20 LH Inc.Drill RC33048LH Included (std HSS)17/64" (6.7mm)Sutton D180 0670 RC43045 RC23042, RC23043 † RC5018810 RC59190M Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. UNF Replacement Parts Thread Size Current Kit (RC) HSS Drill Bit STI Tap Inserts (Pack of 10) Install Tool Tang Break Tool #3-56 RC34538 Included (std HSS)#5 (3.2mm)Sutton D180 0320 RC44535 RC04535 † RC5006117 RC59060M #4-48 RC34548 Included (std HSS)#6 (3.5mm)Sutton D180 0350 RC44545 RC04542, RC04543, RC04544 † RC5007717 RC59080M #6-40 RC34568 Included (std HSS)#8 (4.0mm)Sutton D180 0400 RC44565 RC04562, RC04563, RC04564 † RC5009517 RC59100M #8-36 RC34588 Included (std HSS)#10 (4.8mm)Sutton D180 0480 RC44585 RC04582, RC04583, RC04584 † RC5012514 RC59130M #10-32 RC34608 Included (std HSS)#10 (4.8mm)Sutton D180 0480 RC44605 RC04602, RC04603, RC04604 † RC5015611 RC59140M #12-28 RC34628 Included (std HSS)#11 (4.9mm)Sutton D180 0490 RC44625 RC04622, RC04623, RC04624 † RC5015610 RC59140M 1/4-28 RC34048 Included (std HSS)17/64" (6.7mm)Sutton D180 0670 RC44045 RC04042, RC04043, RC04044 † RC5018810 RC59190M 5/16-24 RC34058 Included (std HSS)21/64" (8.3mm)Sutton D180 0830 RC44055 RC04052, RC04053, RC04054 † RC502508 RC59220M 3/8-24 RC34068 Included (std HSS)13/32" (10.3mm)Sutton D180 1030 RC44065 RC04062, RC04063, RC04064 † RC503136 RC59250M 7/16-20 RC34078 Included (std HSS)29/64" (11.5mm)Sutton D180 1150 RC44075 RC04072, RC04073, RC04074 † RC503443 RC59340M 1/2-20 RC34088 Not included(>13.0mm — outside D180 range) RC44085 RC04082, RC04083, RC04084 † RC503753 RC59380M 9/16-18 RC34098 Not included(>13.0mm — outside D180 range) RC44095 RC04092, RC04093 † RC504380 RC59380M 5/8-18 RC34108 Not included(>13.0mm — outside D180 range) RC44105 RC04102, RC04103, RC04104 † RC504380 RC59380M 3/4-16 RC34128 — RC44125 RC04122, RC04123, RC04124 † RC505000 — 7/8-14 RC34140 — RC44145 RC04142, RC04143, RC04144 † RC50688 — 1-12 RC34160 — RC44165 RC04162, RC04163, RC04164 † RC50750 — 1-14 UNS Special RC3416014 — RC44165 RC2416314 † RC50750 — 1 1/8-12 RC34180 — RC44185 RC04182, RC04183 † RC50875 — 1 1/4-12 RC34200 — RC44205 RC04202, RC04203, RC04204 † RC51000 — 1 3/8-12 RC34220 — RC44225 RC04222, RC04223, RC04224 † RC51063 — 1 1/2-12 RC34240 — RC44245 RC04242, RC04243, RC04244 † RC51063 — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. BSW, BSP, BSF, BA Replacement Parts Thread Size Current Kit (RC) HSS Drill Bit STI Tap Inserts (Pack of 10) Install Tool Tang Break Tool 1/8-40 RC32028 Included (std HSS)3.5mmSutton D180 0350 RC42025 RC02022, RC02023, RC02024 † RC5008919 RC59060M 3/16-24 RC32038 Included (std HSS)5.5mmSutton D180 0550 RC42035 RC02032, RC02033, RC02034 † RC501409 RC59060M 1/4-20 RC32048 Included (std HSS)6.6mmSutton D180 0660 RC42045 RC02042, RC02043, RC02044 † RC501885 RC59190M 5/16-18 RC32058 Included (std HSS)8.3mmSutton D180 0830 RC42055 RC02052, RC02053, RC02054 † RC502507 RC59220M 3/8-16 RC32068 Included (std HSS)10.0mmSutton D180 1000 RC42065 RC02062, RC02063, RC02064 † RC502507 RC59250M 7/16-14 RC32078 Included (std HSS)11.5mmSutton D180 1150 RC42075 RC02072, RC02073, RC02074 † RC503441 RC59340M 1/2-12 RC32088 Not included(>13.0mm — outside D180 range) RC42085 RC02082, RC02083, RC02084 † RC503752 RC59380M 9/16-12 RC32098 Not included(>13.0mm — outside D180 range) RC42095 RC02092, RC02093, RC02094 † RC504380 RC59380M 5/8-11 RC32108 Not included(>13.0mm — outside D180 range) RC42105 RC02102, RC02103, RC02104 † RC504380 RC59380M 3/4-10 RC32128 — RC42125 RC02122, RC02123, RC02124 † RC504380 — 7/8-9 RC32140 — RC42165 RC02142, RC02143, RC02144 † RC50688 — 1-8 RC32160 — RC42165 RC02162, RC02163, RC02164 † RC50750 — 1 1/8-7 RC32180 — RC42185 RC02182, RC02183, RC02184 † RC50875 — 1 1/4-7 RC32200 — RC42205 RC02202, RC02203, RC02204 † RC51000 — 1 3/8-6 RC32220 — RC42225 RC02222, RC02223, RC02224 † RC51063 — 1 1/2-6 RC32240 — RC42245 RC02242, RC02243, RC02244 † RC51063 — 1/8-28 RC31028 Included (std HSS)9.7mmSutton D180 0970 RC41025 RC01022, RC01023, RC01024 † RC503135 RC59190M 1/4-19 RC31048 Not included(>13.0mm — outside D180 range) RC41045 RC01042, RC01043, RC01044 † RC504380 RC59310M 3/8-19 RC31068 Not included(>13.0mm — outside D180 range) RC41065 RC01062, RC01063, RC01064 † RC504380 RC59310M 1/2-14 RC31080 Not included(>13.0mm — outside D180 range) RC41085 RC01082, RC01083, RC01084 † RC504380 RC59380M 5/8-14 RC31100 — RC41105 RC01102, RC01103, RC01104 † RC505000 — 3/4-14 RC31120 — RC41125 RC01122, RC01123, RC01124 † RC505000 — 1-11 RC31160 — RC41165 RC01162, RC01163, RC01164 † RC505910 — 3/16-32 RC30038 Included (std HSS)2.5mmSutton D180 0250 RC40035 RC20032, RC20033, RC20034 † RC5008919 RC59060M 1/4-26 RC30048 Included (std HSS)6.5mmSutton D180 0650 RC40045 RC20042, RC20043 † RC501885 RC59190M 5/16-22 RC30058 Included (std HSS)8.1mmSutton D180 0810 RC40055 RC20052, RC20053, RC20054 † RC502194 RC59220M 3/8-20 RC30068 Included (std HSS)9.7mmSutton D180 0970 RC40065 RC20062, RC20063, RC20064 † RC502507 RC59250M 7/16-18 RC30078 Included (std HSS)11.4mmSutton D180 1140 RC40075 RC20072, RC20073, RC20074 † RC503441 RC59340M 1/2-16 RC30088 Included (std HSS)13.0mmSutton D180 1300 RC40085 RC20082, RC20083, RC20084 † RC503752 RC59380M 9/16-16 RC30098 — RC40095 RC20093 † RC504380 — 5/8-14 RC30108 — RC40105 RC20103 † RC504380 — 3/4-12 RC30128 — RC40125 RC20123 † RC504380 — 7/8-11 RC30140 — RC40145 RC20143 † RC50688 — 1-10 RC30160 — RC40165 RC20163 † RC50750 — 1 1/4-9 RC30200 — RC40205 RC20163 † RC51000 — Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. If the kit you need isn't in the table above (older 2007 or 2013 codes only, or Obsolete status), the parts above are also sold individually and can usually substitute. Ring AIMS with the original kit number — Sam or one of the team will work out the current replacement parts. The standalone insert removal tool — RC50003 Insert Extraction Tool — covers M4 through M24 / #6 through 1" UNC and is essential gear for any workshop doing regular thread repair. AIMS also stocks the threadlockers commonly used after insert installation: see our Loctite 243 guide for medium-strength threadlock applications, and the Loctite 577 guide for pipe thread sealing. Obsolete Kits — Identifying Alternatives 14 kits that appeared in the 2007 and/or 2013 catalogues did not make the cut for 2023. Most were absorbed into range kits or replaced by closer-fitting current sizes. If you've got an obsolete code on an old purchase order, the table below lists each one with a suggested current alternative. When in doubt, contact AIMS — we can usually source the obsolete kit on special order through Recoil/Sutton Tools, or recommend the closest current RC equivalent from the Recoil collection. Thread Size Section Last Known Code (2007/2013) Suggested Current Alternative M9 x 1.0 METRIC MEDIUM THREAD KITS 37090 Contact AIMS — special order or closest current RC kit M11 x 1.25 METRIC MEDIUM THREAD KITS 37118 Contact AIMS — special order or closest current RC kit M10 x 1.5 Pilot Nose PILOT NOSE TAP KITS 35103 Contact AIMS — special order or closest current RC kit V/W range (38008 in 2007) PILOT NOSE TAP KITS 38008 Contact AIMS — special order or closest current RC kit O.P.E. range (38007 in 2007) PILOT NOSE TAP KITS 38007R Contact AIMS — special order or closest current RC kit 1/4-32 UNEF — UNIFIED NATIONAL EXTRA FINE 34040-32 Contact AIMS — UNEF range largely absorbed into UNF / range kits 7/16-24 UNEF — UNIFIED NATIONAL EXTRA FINE 34070-24 Contact AIMS — UNEF range largely absorbed into UNF / range kits 1/4-24 Harley Davidson SPECIAL INCH THREADS — HARLEY, CARBURETTOR, CUMMINS, UN 34040-24 Contact AIMS — special order or closest current RC kit 7/16-16 Harley Davidson SPECIAL INCH THREADS — HARLEY, CARBURETTOR, CUMMINS, UN 34070-16 Contact AIMS — special order or closest current RC kit 7/8-20 Carburettor SPECIAL INCH THREADS — HARLEY, CARBURETTOR, CUMMINS, UN 34140-20 Contact AIMS — special order or closest current RC kit 1-20 Carburettor SPECIAL INCH THREADS — HARLEY, CARBURETTOR, CUMMINS, UN 34160-20 Contact AIMS — special order or closest current RC kit 1-11.5 NPT — NATIONAL PIPE THREAD (TAPERED) 36160 Contact AIMS — closest BSP equivalent or special order 1/4-26 BSC / BRASS — BRITISH STANDARD CYCLE / BRASS THREADS (26 TPI) 30040 Contact AIMS — discontinued thread family, custom sourcing VW range (38008 in 2007) BSC / BRASS — BRITISH STANDARD CYCLE / BRASS THREADS (26 TPI) 38008 Contact AIMS — discontinued thread family, custom sourcing Can't find your kit above? AIMS sources historic, obsolete and special-order Recoil kits direct. Contact us with the part number you need and we'll track it down for you. Why Recoil Renumbered — Understanding the Three Generations Three changes happened over fifteen years. 2007 — the original numbering The 2007 catalogue used 5-digit numeric codes ending in a 0. The first two digits identified the thread family (35 = Metric Coarse, 33 = UNC, 32 = BSW, and so on), the next two coded the size, and the final 0 marked the standard kit. Spark plug trade kits used a hyphenated sub-code (38140 base, 38140-2 for trade pack). 2013 — the suffix shift In 2013 Recoil moved every standard kit's trailing 0 to an 8. The reasoning at the time was inventory and barcode rationalisation — the 8-suffix freed up the 0-suffix codes for bulk and OEM-only variants. Hyphenated spark plug trade codes also shifted (38140-2 → 38148-2). 2023 — the RC prefix The 2023 catalogue added a literal RC prefix to every part number. This was a global brand-consolidation move — Recoil products had been distributed under various sub-brands in different markets, and the RC prefix gave the line a single identifying signature worldwide. Many kits were also re-organised into "Inc.Drill" variants (the matching HSS drill bit packed inside the kit) and a fresh batch of range kits with the R suffix were introduced. Recoil has been a Sutton Tools brand since the early 2000s — Sutton, the Australian-owned engineering tool manufacturer headquartered in Melbourne, owns the Recoil brand globally. That's why you'll see Sutton D180 drill bit codes throughout this guide as the matched replacements — Sutton is making the drill bits that Recoil specifies. AIMS stocks the matching Sutton drills in the Sutton Tools collection. Standards & Specifications Recoil inserts and the holes they fit are governed by a handful of international and Australian thread standards. The kits themselves are manufactured to military and aerospace specifications, which is why Recoil inserts are an accepted repair method on certified aircraft and defence equipment. Thread standards by family AS 1275-1985 (R2017) (Metric Screw Threads for Fasteners) and ISO 965 (ISO Metric Screw Threads — tolerances). and ISO 965 (ISO Metric Screw Threads — tolerances). The diameter and pitch designations in the tables above (e.g. M6 x 1.0) follow ISO 965 nomenclature. UNC and UNF kits — ASME B1.1-2024 (Unified Inch Screw Threads, UN/UNR/UNJ Thread Forms). Defines the #2-56 through 4-4 thread series Recoil supplies kits for.. Defines the #2-56 through 4-4 thread series Recoil supplies kits for. BSW and BSF kits — BS 84:2007 (Parallel Screw Threads of Whitworth Form — Requirements). Standard remains active for legacy/restoration applications.. BSP kits — ISO 228-1 (Pipe threads where pressure-tight joints are not made on the threads) for parallel BSP. BS 21 / ISO 7-1 for tapered BSPT variants. NPT kits — ANSI/ASME B1.20.1-2013 (R2018) (Pipe Threads, General Purpose, Inch).. BA kits — BS 93:2008 (British Association Screw Threads — Requirements). Standard remains active; BA series retained for instruments, clocks and legacy work (M-series preferred for new designs).. Insert manufacturing standards NASM 33537 (formerly MIL-S-7742) — the US National Aerospace Standard governing helical coil thread inserts. Recoil inserts are manufactured to NASM 33537 for the Free Running grade. NASM 8846 (formerly MIL-I-8846) — covers screw-locking (locking) helical coil inserts, with the polygonal locking coil. Recoil inserts in stainless steel are manufactured from 304 stainless steel as standard, with Inconel X-750 available for high-temperature applications (exhaust manifolds, turbocharger housings, gas turbine components — service temperatures above 425°C). If you're specifying Recoil for a certified application (aviation, defence, rail, pressure-rated industrial), contact AIMS — we can supply NASM-compliant certification paperwork on request. How AIMS Sources Recoil AIMS Industrial stocks the full current Recoil range as an authorised Australian distributor. The Recoil collection at AIMS includes: Single-size thread repair kits in metric, UNC, UNF, BSP, BSW, BSF, BA and spark plug threads — the standard workshop kits with everything needed for one specific size. Range kits — multi-size cases for trade and workshop use. RC35004R (M5–M12), RC35005R (M6–M16), RC33004R (1/4–1/2 UNC), RC34004R (1/4–1/2 UNF), RC32004R (1/4–1/2 BSW), RC30004R (1/4–1/2 BSF). Spark plug kits — RC381082, RC381202, RC38140, RC381482, RC38188, plus the in-vehicle RC38148 Plug Saver. Replacement inserts — sold in packs of 10 as variants of Recoil Insert — Metric 304 Stainless Steel, UNC, UNF, plus bulk 05xxx packs for high-volume users. STI taps — Taper, Intermediate and Bottoming styles in metric and UNC. Install & tang break tools — manual install tools (RC5006121, RC5008917, RC5006917, etc.) and magnetic tang break tools (RC59060M, RC59070M, RC59080M). Insert extraction — RC50003, covering M4 through M24 / #6 through 1" UNC. Keysert Light — solid-bushing inserts for higher load applications. Recoil Keysert Light — Metric Stainless Steel. For Obsolete (2007/2013-only) kits, POA kits, and historic codes that don't have a direct current equivalent, AIMS has a special-order channel direct to Recoil/Sutton Tools — lead times are usually 2–4 weeks. Ring (02) 9773 0122 with the original code and we'll source it. Trade and procurement accounts are available — automatic credit for government bodies, defence prime contractors and Tier-1 customers. Contact us or apply for a trade account. Found your code? Get your kit. Shop Recoil thread repair kits at AIMS — all current RC codes stocked AIMS Industrial is an authorised Recoil stockist carrying the current 2023 RC-prefix kits for metric M3–M14 and UNC threads — available for fast Australia-wide dispatch. Not sure which code you need? Our team can help match your old part number. Shop Recoil at AIMS Thread repair guide Talk to a specialist Frequently Asked Questions What's the difference between 2007, 2013 and 2023 Recoil part numbers? Recoil changed its catalogue numbering twice. In 2013 the trailing 0 on every standard kit code was changed to an 8 (e.g. 35060 became 35068). In 2023 a literal RC prefix was added to every part number (e.g. 35068 became RC35068). The kit itself — thread size, insert, drill, tap, install tool — is functionally the same across all three generations. Only the part number changed. What does the RC prefix mean on Recoil kits? RC simply stands for Recoil. It was added globally in 2023 as a brand-consolidation move so every Recoil product has the same identifying prefix worldwide. The number after the prefix is unchanged from the 2013 catalogue. Can I still buy Recoil kits with old part numbers? Old numbers (the 2007 and 2013 codes) won't appear in any current Recoil price list, but the equivalent current RC kit is almost always available. Use the tables in this guide to translate your old code to the 2023 RC code, then search the AIMS Recoil collection or ring (02) 9773 0122. For genuinely obsolete kits (about 14 in the catalogue), AIMS can usually special-order through Recoil/Sutton Tools — lead times around 2–4 weeks. What does 'POA' mean on Recoil kits? POA stands for Price on Application. The kit is still listed by Recoil and can be supplied, but pricing isn't published in the standard 2023 catalogue — usually because it's low-volume, specialty, or built to order. Around 17 kits sit in POA status (mostly large sizes like 1.5" BSW and 2" UN, plus Cummins and Harley Davidson specialty threads). Contact AIMS with the part number for a quote. Which Recoil kits are now obsolete? 14 kits that were in the 2007 or 2013 catalogues are not listed in 2023. Most are vintage British Standard Cycle (BSC) and Brass 26 TPI threads, some UNEF sizes that were absorbed into range kits, and a few Harley Davidson and NPT specialty kits. See the Obsolete Kits table in this guide for the full list with suggested current alternatives. How do I find the current RC code for an old Recoil part number? Find the row in the relevant thread family table above that lists your old code in the 2007 or 2013 column. The 2023 Part No. column gives you the current RC code. If the row shows an em-dash in the 2023 column, the kit is obsolete — see the Obsolete Kits section for alternatives. What's included in a standard Recoil thread repair kit? A standard Recoil kit contains: an STI (Screw Thread Insert) tap sized for that thread; a pack of inserts (usually 5 or 10 depending on the kit); a manual install tool for that thread size; and a tang break tool to snap off the insert's installation tang once it's seated. Some 2023 kits are 'Inc.Drill' variants which also include the matching HSS drill bit in the case. Do I need a special tap to install Recoil inserts? Yes — Recoil inserts require an STI (Screw Thread Insert) tap, which cuts a slightly larger thread than a standard tap to accept the insert. You can't substitute a standard tap. AIMS stocks STI taps in Taper, Intermediate and Bottoming styles for both metric and UNC threads. The Intermediate style is the general-purpose choice for most repair work. What drill bit size do I need for a stripped M6 thread? For Recoil RC35068 (M6 x 1.0), the drill bit size is 6.3mm HSS — Sutton D180 0630 is the AIMS-matched part. The drill is included in the 2023 'Inc.Drill' variants. For other thread sizes, see the Replacement Parts tables in this guide. The drill must be HSS minimum — carbide is fine but high-speed steel is the standard and what Recoil specifies. What's the difference between Free Running and Screw Locking Recoil inserts? Free Running inserts (manufactured to NASM 33537, formerly MIL-S-7742) are smooth helical coils — the most common type and what's supplied in standard kits. Screw Locking inserts (NASM 8846, formerly MIL-I-8846) have one or more polygonal locking coils that grip the male thread, providing vibration resistance without needing thread-locking adhesive. Locking inserts are common in aerospace, defence and motorsport applications. What's a Tanged vs Tangless Recoil insert? Tanged inserts have a small driving tang at the bottom that the install tool engages with — once the insert is seated, you use a tang break tool to snap the tang off. Tangless inserts have no tang and are installed with a special tool that grips the insert internally. Tangless is preferred where the tang could fall into a sensitive cavity (engine internals, hydraulic galleries). Most standard Recoil kits use Tanged inserts; Tangless is supplied for specific applications on request. Can I install Recoil inserts by hand or do I need a power tool? Hand install is the standard method and what every Recoil kit is designed for — the manual install tool is included. Power install is possible for high-volume production work but isn't recommended for one-off repairs because over-torquing can damage the insert or the parent material. For workshop use, the manual install tool gives the right feedback to know when the insert is correctly seated. What's the difference between standard and Inconel Recoil inserts? Standard Recoil inserts are 304 stainless steel — fine for service temperatures up to around 425°C. Inconel X-750 inserts are specified for high-temperature applications above 425°C: exhaust manifolds, turbocharger housings, gas turbine bosses, industrial furnace fittings. The Inconel inserts cost significantly more and are usually special-order — contact AIMS for current availability and pricing. Does AIMS stock the Recoil RC part I need? AIMS keeps the most-used Recoil kits in stock at our Milperra warehouse: single-size kits in metric M3–M30, UNC 1/4–1", UNF 1/4–3/4", BSP 1/8–1/2", common BSW sizes, and all five spark plug kits. Range kits for metric, UNC, UNF, BSW and BSF are also in stock. Less common sizes, Inconel inserts, and Obsolete/POA kits are special-order with lead times of 2–4 weeks. Ring (02) 9773 0122 to confirm stock before ordering. What if my Recoil kit is obsolete and there's no current equivalent? About 14 kits in the catalogue are flagged as Obsolete — they appeared in the 2007 or 2013 catalogues but aren't in 2023. For most, a closely related current RC kit will work (a UNEF kit absorbed into a UNF range kit, for example, or a BSC thread that's now special order). AIMS can also source genuinely obsolete kits through our direct Recoil/Sutton Tools channel — lead times 2–4 weeks. Ring (02) 9773 0122 with the original code and we'll work out the best path. Need a Recoil Kit or Replacement Part? AIMS Industrial stocks the full current Recoil range and can special-order obsolete kits and Inconel inserts through our direct Recoil/Sutton Tools channel. Browse the Recoil collection, see the matched Sutton Tools drill bits, or read more on the stripped threads guide for thread-repair fundamentals. Phone: (02) 9773 0122 · Contact us via our contact page · Warehouse: 108 Ashford Ave, Milperra NSW 2214 (Mon–Fri 07:30–15:30 dispatch, 08:00–17:00 phone). Cross-reference data compiled by AIMS Industrial from the Recoil 2007 catalogue, the 2013 Australian Price List, and the 2022/2023 catalogue. Validated against current Recoil/Sutton Tools stock. Last updated 18/06/26. See AIMS's full metric thread forming taps range — trade pricing and Australia-wide despatch.
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How to Identify High Tensile Bolts for Your Projects
Quick & Easy: How to Identify High Tensile Bolts When your project demands extra strength – whether it's for a vehicle upgrade or heavy machinery – high tensile bolts are a must. At AIMS Industrial, we’re here to help you understand what to look for in a fun and easy way. Understanding Bolt Grades Bolt grades indicate the strength and durability of the bolt. In Australia, you will commonly encounter these grades: Grade Description 8.8 Medium carbon steel, quenched and tempered 10.9 Alloy steel, quenched and tempered for extra strength 12.9 Alloy steel with the highest tensile strength How to Identify High Tensile Bolts Look for the grade markings stamped on the bolt head – these numbers tell you the bolt’s strength: 8.8: Marked with "8.8" 10.9: Marked with "10.9" 12.9: Marked with "12.9" Choose the Right Bolt for Your Application Not every project requires the same level of strength. Here are some of our top picks available at AIMS Industrial: Metric Hex Bolt - Grade 8.8 High Tensile Zinc Finish – Ideal for many structural applications. Bumax 10.9 Stainless Steel High Tensile Hex Bolt – Perfect for projects needing extra corrosion resistance. M20 x 24 x 80 Socket Head Shoulder Screw Plain High Tensile G12.9 – The top choice when maximum strength is essential. Safety, Time and Money Selecting the right high tensile bolt is crucial for the safety and longevity of your projects. Always check the bolt head for grade markings and choose the one that best fits your application. Explore our full range of high-quality fasteners on our Bolts Collection for more options. For a comprehensive guide CLICK HERE At AIMS Industrial, we make sure you have the right tools for every project. Happy bolting! People Also Ask — High-Tensile Bolt Identification Q: How can I tell if a bolt is high-tensile? The quickest way is to read the head markings. Metric high-tensile bolts carry a property class number stamped on the head, such as 8.8, 10.9 or 12.9 — the higher the number, the stronger the bolt. Imperial bolts use radial lines on the head, where more lines indicate a higher grade. A bolt with no markings is generally a low-grade commercial fastener and should not be assumed to be high-tensile. So before relying on a bolt for a structural or high-load joint, check the head: a clear property class number or a set of radial lines tells you it is a graded, high-tensile fastener rather than a general-purpose one. Q: What do the numbers like 8.8, 10.9 and 12.9 mean? These are metric property class markings, and they encode the bolt's strength. The first number relates to the bolt's tensile strength and the second to its yield strength as a proportion of tensile, so a higher pair of numbers means a stronger, harder bolt. In practice, 8.8 is the common high-tensile grade for general engineering, 10.9 is used for more demanding joints, and 12.9 is among the highest standard grades for the most heavily loaded applications. The system lets you compare bolts at a glance — a 10.9 is stronger than an 8.8 — which is why matching the property class to the joint's requirement matters. Q: How do imperial bolt grade markings work? Imperial bolts show their grade through radial lines stamped on the head rather than numbers. No lines indicate a low-grade bolt, three radial lines indicate a common medium-high grade, and six radial lines indicate a higher grade again — more lines means a stronger bolt. Because the markings differ from the metric number system, it is important not to confuse the two: an unmarked head is not the same as a graded metric bolt. When working in imperial, count the radial lines to read the grade, and confirm against the supplier's specification if the joint is critical. Mixing up imperial and metric grade systems is a common and avoidable error. Q: Why does using the correct bolt grade matter? Bolt grade determines how much tension and shear a fastener can safely carry. Using a bolt that is too low a grade in a high-load joint risks the bolt yielding or failing, which in structural, lifting or machinery applications can be dangerous. Conversely, the grade affects the correct tightening torque, so fitting the wrong grade and torquing it as if it were another can over- or under-stress the joint. Matching the bolt's property class or grade to the engineering requirement — and torquing it accordingly — is what keeps the joint safe and reliable. When a joint is critical, always confirm the specified grade rather than substituting whatever is on hand. Q: Can I substitute a higher-grade bolt for a lower one? It is often acceptable to use a higher-grade bolt where a lower grade is specified, since the stronger bolt has greater load capacity — but it is not automatic. Higher-grade bolts are harder and can be more brittle, the correct tightening torque changes with grade, and some applications deliberately specify a particular grade for reasons such as controlled failure or ductility. Going the other way — substituting a lower grade where a higher one is called for — should never be done, as it under-rates the joint. The safe rule is to match the specified grade where you can, and only step up after confirming the higher grade and its torque suit the application. For champion, see our champion range stocked across Australia. Need bumax? Browse the AIMS range at bumax.
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Socket Drive Size Guide: 1/4", 3/8", 1/2" & 3/4"
Drive size is directly related to socket size (view size chart here), but in a way that relates to strength and torque rather than the actual size of the fastener head the socket fits. Specifically: Drive size: This refers to the square-shaped hole/opening in the center of a socket that connects it to the ratchet or other driving tool. It determines the size of the driving tool that can be used and the amount of torque it can handle Socket size: This refers to the opening size of the socket that fits around the head of a fastener (nut, bolt etc). There's a general correlation and some key considerations: Designed for* Torque Requirements Accessibility Larger Drive Size Larger fasteners and applications requiring higher torque Have a larger drive hole to fit a bulkier and sturdier driving tool Can withstand greater force High torque applications such as automotive repairs, heavy machinery or construction Can be bulkier, limiting access in certain situations Small Drive Size Smaller fasteners and lower torque applications Have a smaller square hole to fit a more compact driving tool Low to medium torque applications such as working on electronics, small engines or bicycles Often have thinner profiles, making them better for reaching tight spaces or working in confined areas *As an analogy, think of a screwdriver. A small, delicate screwdriver wouldn't be ideal for turning a large screw that requires a lot of force. Similarly, a small drive size socket wouldn't be suitable for a large bolt that needs significant torque to tighten or loosen. The drive size of a socket is crucial for ensuring proper fit, torque and accessibility. Drive size dictates the strength and torque capacity of the socket-and-ratchet combination, while the socket size itself determines which fastener head it can fit. Common drive sizes and their uses: 1/4" drive: Ideal for small fasteners, electronics and light-duty tasks 3/8" drive: Versatile for a wide range of applications, including light (non-engine) automotive work and home repairs 1/2" drive: Suitable for heavy-duty tasks, such as lug nut removal and engine work for light vehicles 3/4" drive: Suitable for more heavy-duty applications, such as lug nut removal and engine work for medium-sized (to some heavy) vehicles and industrial equipment 1" drive: Suitable for even heavier duty applications that require significant torque, such as lug nut removal and engine work for heavy vehicles and industrial machinery It's often beneficial to have a variety of drive sizes in your toolkit to handle different tasks effectively. Need another reference chart? Browse the full AIMS Engineering Reference Charts library — drill bit sizes, tap drill, torque, viscosity, GD&T, AS/NZS standards and more. AIMS' Note on Safe Use of Hand Tools Inspection: Before using any tool, carefully inspect it for cracks, chips, loose handles, worn / mushroomed heads or any other signs of damage. Damaged or defective tools may cause harm! Ensure all guards are in place. Right tool for the job: Make sure you understand the intended purpose of each tool and choose the correct one for your specific job. Don't try to make a screwdriver work as a pry bar or a wrench as a hammer. Safe handling: Carry sharp tools pointed down and away from your body. Never carry tools in your pockets where they can cause injury. When passing a tool to someone, extend the handle first. PPE: Wear safety glasses or goggles to protect your eyes from flying debris. Consider gloves depending on the tool and task to prevent cuts or blisters but without compromising comfort, dexterity and protection. If working with noisy tools, wear ear protection. Maintenance: Keep your tools clean, sharp and properly maintained. Store them in a safe and organised place when not in use. For metric bolt torque values (M3-M36, grade 4.6 through 12.9), see our Metric Bolt Torque Chart. People Also Ask — Socket Drive Size Guide: 1/4", 3/8", 1/2" & 3/4" Q: What is the difference between 3/8" and 1/2" drive sockets? Drive size refers to the square drive that connects the socket to the ratchet — 3/8" is the most versatile for general trade work, while 1/2" drive handles higher torque applications like wheel nuts and structural bolts. 1/4" drive suits tight spaces and small fasteners; 3/4" and 1" drive are for heavy industrial work. Q: Can I use a metric socket on an imperial bolt? In a pinch, a close-fitting metric socket can work on an imperial fastener — for example, a 14 mm socket is nearly identical to 9/16". However, using a slightly oversized socket risks rounding off the fastener corners. Always use the correct size where possible; keep a mixed metric/imperial set for older equipment. Q: What is the difference between 6-point and 12-point sockets? A 6-point socket has six contact surfaces and grips flat-to-flat on the hex, reducing the risk of rounding fasteners. A 12-point socket engages on corners, making it easier to position in tight spaces but more likely to slip under high torque. Use 6-point sockets for stuck or high-torque fasteners; 12-point for easy access work. Q: Are impact sockets different from standard sockets? Yes — impact sockets are made from thicker, softer chrome-molybdenum steel that absorbs the hammering action of an impact wrench without shattering. Standard chrome-vanadium hand sockets can crack under impact loads. Impact sockets are typically black (not chrome-plated) for easy identification. Never use hand sockets with impact guns. Need strong hand? Browse the AIMS range at strong hand.
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How to Identify Synchronous Timing Belts
In an ideal situation, you can identify the belt you have by its markings alone. Typically, those are alphanumeric labels that identify the belt's specifications, often describing the most important dimensions critical to properly identify them. (In another article, we discussed how you can identify a v-belt.) Important: If your pulley has teeth, then you indeed have a synchronous timing belt, which should not be mistaken for cogged belts -- who also appear like they have "teeth" but are just actually cogs (notches) -- such as these banded-narrow, classical and narrow-section cogged belts. For example, in Gates nomenclature, in their PowerGrip range, you’ll see a marking that designates the belt’s pitch length, pitch and tooth profile (the letters), and the width. (Image taken from the Gates Industrial Power Transmission Catalog) Note: This applies to both single-side and double-sided synchronous belts. Nomenclature and order may vary by manufacturer. You may, however, be in a situation where you don’t have access to that information for many reasons, such as: The belt is still installed in the pulley and there’s no way you can see the markings. The belt is already snapped and torn. The markings are too faded or dirtied to be read. In this case, you may have to manually figure out your belt specifications. We hope this article points you in the right direction. Here are the 3 key identifiers you need to determine to order the belt: 1. What is the tooth profile of the belt? 2. What is the length? 3. What is the width? Timing Belt Measurement — Quick Reference Synchronous timing belts are identified by three measurements: tooth pitch (distance between adjacent tooth centres in mm or inches), belt length (total circumference in mm or number of teeth), and belt width (across the toothed face in mm). Together these tell you the exact belt — for example "8M-1200-30" means 8mm pitch, 1200mm length, 30mm width. Measurement What it is How to measure Pitch Distance between tooth centres Measure tooth-to-tooth in mm (metric) or 1/inch (imperial) Length Total belt circumference Lay belt flat, measure outside circumference; or count total teeth Width Across the toothed face Measure the belt width perpendicular to the teeth Tooth count Number of teeth around the belt Count all teeth — used in part numbers 1. What is the tooth profile of the belt? This is the most important identifying factor of synchronous belts, so it’s important to get this right. If you get the wrong profile, it may not fit the pulley at all and, if it does, it will wear out very quickly. You can tell the profile of the belt by its pitch and shape. You can also measure the thickness as a cross-check. Pitch This is the “centre-to-centre" distance between two adjacent teeth. To get this number, measure the distance between the middle of one tooth, to the middle of the adjacent tooth. Imperial vs Metric: This is another key factor in finding the type of belt you have, so it’s equally important to get this right. Important: When manually measuring the pitch, please make sure to use the metric system (eg. by millimeters), as we often do here in Australia. Otherwise, let us know that you’re giving us the measurement in imperial, so we can help you work out its metric equivalent. In this sample reference from the Gates PowerGrip range, you’ll see the pitch is indicated in imperial units (eg. 1/5 inch), as it would be typically written. (Image taken from the Gates Industrial Power Transmission Catalog) Here’s another reference from the Gates PowerGrip timing belt range. Note that this range is imperial but, for ease, dimensions are shown in both imperial and metric units. In this illustration, label A is the pitch. (Image taken from the Gates Industrial Power Transmission Catalog) Aside from the belt, don’t forget to check the pulleys for any markings too. The pulley won’t give you everything you need to order the belt but they often have the pitch/profile printed on them. If so, this will make life a lot easier. It also helps a lot because, occasionally, we find that someone has previously fitted the wrong belt, so checking the pulley is a great way of ensuring you’re getting the right belt. Shape This is how the angles of the peaks and valleys in between the teeth look like, as well as the shape of the tooth. Some belts have rounded teeth, whilst others are quite ‘square’ or trapezoidal. Some people refer to this as the tooth form. Metric belts usually have rounded teeth, while imperial belts have trapezoidal ones, but keep in mind that is not always the case. If you’re having trouble and need our help identifying the belt, we won’t need the exact angle of the shape, but as always, it will be helpful if you can send a photo of the actual belt that needs replacing, as well as the pitch as accurately measured as possible. Thickness Aside from the shape, this value will help us get a better understanding of the belt you have. Although it’s more challenging to get this exactly right considering the wear on the belt. Warning: Don’t be confused by the T and AT profiles (eg T10 & AT10). As you can see in the illustration below, the Ts are more trapezoidal, while the ATs are more rounded. Both, of course, have the same Pitch (eg. 10mm) but the shape is very different. If in doubt, send us a photo of the actual belt and we’ll help you figure it out. (Image taken from the Gates Industrial Power Transmission Catalog) 2. What is the length? Sometimes also referred to as pitch length, this is the total (circumferential) length of the belt, as measured along the pitch line. Put simply, this is the pitch (see #1) multiplied by the number of teeth the belt has. For example, if your belt has a pitch of 10 mm and 32 teeth, then your pitch length is 320 mm. Tip: Mark the tooth where you are going to start counting, and count carefully from there. Some even make subtle marks for every 10th tooth, so it’s easy to go back (and verify) in case you lose count. If possible, get someone else to count as well and then cross-check. We do that with every belt to avoid errors. If you don’t have someone else to check it, then count it yourself 2 or 3 times to ensure you have it right. Special case for imperial belts: Imperial belt pitch lengths are marked in imperial by 1/100 or 1/10 of an inch (in decimal inches). Naturally larger belts are measured in 1/10 and smaller in 1/100. Here is an example from Gates: That means it’s 2.88 inches long and it’s listed this way in the table where you’ll see its metric equivalent of 73.15 mm: 3. What is the width? Measuring this is pretty much straightforward. Just bear in mind that the belt may be a little worn. (Timing belt 3D view illustration courtesy of Pfifer) Special case for imperial belts: Imperial belt widths are identified in decimal inches, as in the previous example by Gates: In this example, the belt width is 0.19 inches. Furthermore, if it were 050, then that would be 0.50 inches. Or 0.75 inches. 100 would be 1 inch and so on. Other factors to consider In addition to those three questions, we may occasionally need to confirm the following: What’s the application? Even when two belts are dimensionally the same, one may be stronger than another and therefore designed to withstand heavier loads (eg. for systems with forced induction mechanisms such as superchargers). Are you sure it’s not a cogged V belt? The 'cog's or notches in cogged V belts make it "look like they have teeth", but they actually go into a pulley with no teeth. To emphasise, if the pulleys have no teeth, then it isn’t a timing belt. It is then typically a cogged V belt or, occasionally, a Variable Speed belt. What is the belt made of? Most are made of rubber, while some are made of aramid, neoprene, carbon fibre, polycarbonate or polyurethane. Some are strong enough they can replace chains, provided they can fit in the proper (or appropriately converted) sprockets. For more information, you can refer to these catalogues by Gates: Gates Belts ID Chart Gates Industrial Power Transmission Catalogue Conclusion Measure your belt pitch. From there, identify your tooth profile. Measure your belt length by counting the number of teeth and multiplying it by the pitch. Measure your belt width. In addition, it’s best if you can identify: The intended application The material of the belt If in doubt, just reach out to us and we’ll help you figure it out. It would be helpful if you can include pictures of the actual belt you want to replace and any measurements you’ve taken. AIMS' Note on Safe Use of Belt-Driven Systems Power down: Before any inspection, maintenance, or adjustment, make sure to completely shut down the power to the machine and apply a lockout/tagout (LOTO) device to prevent accidental restarts. Right belt for the system: Keep in mind that v-belts (especially cogged / notched / wrapped belts) are different from synchronous /timing / ‘toothed’ belts. Some mistake the cogs for teeth but remember that cogged belts run on V-shaped pulleys that do not have teeth. Are you operating where flammable substances are present? Maybe you need fire-resistant anti-static (FRAS) belts – or maybe heat-resistant and oil-resistant belts will do. We compared them in this FAQ. Safe attire: Avoid loose clothing, jewelry and long hair that could get caught in the moving parts. Ensure proper fit of workwear without compromising comfort, dexterity and protection. Tie back long hair and secure loose items. Safeguards in place: Never operate a belt-driven system with the guards removed or bypassed. These guards are there for your protection. Maintenance and replacement: Regularly inspect belts and pulleys for wear and tear. Maintain proper belt tension and alignment as specified by the manufacturer. When replacing the belt, make sure you get the proper fit and measurement of the system. These accessories and maintenance kits (eg alignment tools, belt measurers, pulley gauge sets, spacers, tensioners etc) come in handy. Cleanliness: Keep the area around belt drives free of debris and clutter that could get caught or cause a fire hazard. (Refer to our content library's sub-index of articles about belt-driven systems and electric motors for more information.) Our V-Belt Measurement guide shows how to identify and size every common Australian V-belt profile. People Also Ask — Measuring Synchronous Timing Belts Q: How do I determine the pitch of a synchronous timing belt? Timing belt pitch is the distance from the centre of one tooth to the centre of the next tooth, measured along the belt's pitch line. Measure across several teeth and divide by the number of spaces to get an accurate average. Common metric pitches include 3mm, 5mm, 8mm and 14mm; common imperial pitches include 0.080 inch (XL), 0.125 inch (L) and 0.200 inch (H). Q: How do I measure the length of a synchronous timing belt? Wrap a flexible steel rule or string around both pulleys with the system assembled and under correct tension, then measure the total loop length. For an existing belt, count the number of teeth and multiply by the pitch to get the belt's pitch length, which is the standard way timing belt length is specified. Always compare the tooth count and pitch against the manufacturer's replacement specification. Q: What is belt width and why does it matter? Timing belt width determines how much torque the belt can transmit, as a wider belt carries more load for the same pitch and tooth profile. Belt width must match the pulley face width; if the belt is significantly narrower than the pulley it may track off to one side, and if it is wider it may not be compatible with flanged pulleys. Always replace with the same width unless deliberately upgrading for higher load capacity. Q: Can I replace a timing belt with a different tooth profile? No, the tooth profile of the belt must exactly match the pulley. Mixing tooth profiles, for example installing an HTD belt on a trapezoidal-profile pulley, results in poor tooth engagement, premature wear and possible tooth stripping under load. The belt and pulley must always be the same profile family. For timing pulleys, see our timing pulleys range stocked across Australia.
Read moreThread Identification Guide: BSP, NPT, Metric, UNC, Whitworth & ACME
Thread Identification Quick Reference Use this table as your first check when identifying an unknown thread. The thread angle column is the fastest field identification method — 55° is always British-heritage (BSP or BSW), 60° is always American or metric. Standard Origin Thread Angle Profile Form Common AU Usage Key Identifying Feature BSP (BSPP/BSPT) British 55° Rounded crests & roots (Whitworth form) Hydraulics, compressed air, plumbing in AU/UK/EU 55° angle; nominal size = pipe bore, not thread OD NPT American 60° Flat crests, rounded roots US-import equipment, oilfield, pneumatic gear 60° angle + 1:16 taper; often confused with BSPT UNC / UNF American 60° Symmetric parallel (flat crests, flat roots) Imperial fasteners, US machinery, aerospace (UNF) 60° + specified in TPI; UNC coarser, UNF finer Metric M-series International (ISO) 60° Symmetric parallel (flat crests, rounded roots) All new AU manufacturing and imported equipment 60° + pitch in mm (not TPI); e.g. M10 × 1.5 BSW British 55° Rounded crests & roots (Whitworth form) Pre-1970s AU/British machinery, classic vehicles 55° + coarser pitch than BSF; shared TPI with UNC at some sizes BSF British 55° Rounded crests & roots (Whitworth form) Pre-1970s British vehicles, aviation legacy hardware 55° + finer pitch than BSW at same nominal size ACME American 29° Trapezoidal (flat top, flat root, angled flanks) Lead screws, vices, lathes, linear actuators Wide flat-topped thread visible to eye; 29° flanks Tr (Trapezoidal metric) International (ISO) 30° Trapezoidal (metric sizing) European CNC equipment, metric lead screws Wide flat-topped thread; 30° flanks; metric diameter notation If you've ever tried to thread a BSP fitting into an NPT port and felt it cross-thread, or wondered why an "imperial" thread won't bite into a metric hole — you've hit the wall every Australian tradie eventually meets: thread standards are not interchangeable. This guide breaks down the five major thread standards you'll encounter in Australian workshops, mines, factories and farms, and shows you how to identify each one before you ruin a fitting or a thread. Bookmark our Engineering Reference Charts hub for related sizing tables, conversion charts and Australian standard references across 9 topic clusters. Thread Standards — Quick Reference Standard Full Name Thread Angle Form Where You'll Find It BSP British Standard Pipe 55° Parallel (BSPP) or Tapered (BSPT) Plumbing, hydraulics, compressed air in AU/UK/EU NPT National Pipe Taper 60° Tapered (1:16) US-import equipment, oilfield, some pneumatic gear UNC Unified National Coarse 60° Symmetric parallel General-purpose imperial fasteners, US/AU/UK UNF Unified National Fine 60° Symmetric parallel Precision fasteners, automotive, vibration applications BSW British Standard Whitworth 55° Symmetric parallel Legacy Australian/British machinery, classic vehicles Key rule: the thread angle is the dead giveaway. Anything 55° is British heritage (BSP, BSW). Anything 60° is American or metric (NPT, UNC, UNF). Metric M-series is also 60°. For tap drill sizes for each standard, see our Tap Drill Size Chart (Metric & Imperial). For metric vs imperial fastener cross-references, see our Metric vs Imperial Fastener Guide. Why Thread Standards Matter Force a BSP male into an NPT female and you'll get a few turns of "almost right" before it binds, strips or cracks the casting. Force an NPT male into a BSP port and you'll either leak under pressure or split the receiving fitting. The cost ranges from a $5 replacement fitting to a multi-thousand-dollar pump housing — depending on what you've just destroyed. The problem is that thread standards share nominal sizes but use entirely different geometries: Different thread angle — 55° vs 60° means the peaks and valleys don't mesh Different pitch (TPI) at the same nominal size — even where the angle matches, the pitch may not Different sealing geometry — tapered threads seal by metal-to-metal interference, parallel threads need a separate seal Different nominal-size convention — BSP sizes refer to nominal bore, NPT sizes refer to a related but different reference An "M8" bolt and a "5/16" bolt look similar in your hand. They are not interchangeable. The same applies to thread standards in pipes and fittings. BSP — British Standard Pipe BSP (British Standard Pipe) is the dominant pipe thread standard across Australia, the UK, Europe, India, South Africa and most former British Commonwealth countries. If you're working with plumbing fittings, hydraulic fittings, compressed-air fittings, or pneumatic equipment in Australia, the default is BSP unless explicitly stated otherwise. BSP uses a 55° Whitworth thread form with rounded crests and roots. There are two BSP variants you need to know. BSPP — British Standard Pipe Parallel BSPP threads run straight along the length of the pipe (parallel — not tapered). The thread itself does not provide a seal; you need a separate sealing method, typically: Bonded seal washer (Dowty seal) — rubber-bonded steel washer compressed under the fitting head O-ring seated in a port face Flat washer with sealant BSPP is governed by ISO 228 (adopted in Australia as AS ISO 228). You'll see it on hydraulic adapters, compressed-air fittings, and most pneumatic gear in Australian workshops. BSPT — British Standard Pipe Taper BSPT threads are cut on a 1:16 taper (the same taper as NPT, which causes endless confusion — see below). The taper means the thread itself creates the seal as the male fitting wedges into the female port. PTFE tape or thread sealant is wound onto the male thread to fill the small voids and prevent capillary leaks, but the metal-to-metal taper does most of the work. BSPT is governed by ISO 7-1 (adopted as AS ISO 7). You'll see it on iron and brass pipe fittings, particularly water and gas plumbing. Australian BSP Size Reference Nominal Size TPI Pitch (mm) Male OD (mm) Tap Drill (mm) 1/8" 28 0.907 9.728 8.8 1/4" 19 1.337 13.157 11.8 3/8" 19 1.337 16.662 15.25 1/2" 14 1.814 20.955 19.0 3/4" 14 1.814 26.441 24.5 1" 11 2.309 33.249 30.75 1-1/4" 11 2.309 41.910 39.5 1-1/2" 11 2.309 47.803 45.25 2" 11 2.309 59.614 57.0 Critical detail: the BSP "size" is the nominal bore of the pipe it was originally designed for — NOT the actual diameter of the thread. A 1/2" BSP male thread has an outside diameter of approximately 21mm, not 12.7mm. This trips up tradies new to imperial pipe threading every single day. The tap drill column applies to BOTH BSPP and BSPT — the receiving hole is the same size; only the tap profile differs. For BSP fittings in stock, see our Brass Fittings, Iron Pipe Fittings, and Pipe Fittings collections. NPT — National Pipe Taper NPT (National Pipe Taper) is the American pipe thread standard. It's governed by ANSI/ASME B1.20.1. In Australia you'll encounter NPT mostly on imported equipment — particularly air compressors, hydraulic pumps, oilfield gear, and some American-made pneumatic tools. NPT uses a 60° symmetrical thread form with sharp crests and roots — completely different geometry from BSP's 55° rounded thread. Both NPT and BSPT use a 1:16 taper (3/4 inch per foot), which means the OD reduces as you move along the thread. That shared taper is the source of most BSP/NPT confusion — they look interchangeable, they bind for a few turns, then the angle mismatch ruins everything. NPT is ALWAYS tapered. There is also a parallel American thread (NPSF / NPSH / NPSM) but it is much less common — when someone says "NPT" they mean the tapered version. NPT Size Reference Nominal Size TPI Pitch (mm) Male OD at gauge plane (mm) Tap Drill (mm) 1/8" 27 0.941 10.272 8.6 1/4" 18 1.411 13.616 11.1 3/8" 18 1.411 17.055 14.5 1/2" 14 1.814 21.223 17.75 3/4" 14 1.814 26.568 23.25 1" 11.5 2.209 33.228 29.5 1-1/4" 11.5 2.209 41.985 38.0 1-1/2" 11.5 2.209 48.054 44.0 2" 11.5 2.209 60.092 55.5 Compare the BSP and NPT tables above and you'll see why they don't mix — at the same nominal size, the OD, TPI and tap drill are all subtly different. They're close enough to start threading. Close enough to fool a hurried tradie. Not close enough to seal. UNC vs UNF — Unified National Coarse vs Fine UNC and UNF are American imperial fastener thread standards (not pipe). Both use a 60° symmetric thread form, the same as metric M-series. The difference is purely the pitch — UNC has fewer threads per inch (coarse), UNF has more threads per inch (fine). Governed by ANSI/ASME B1.1. Common in Australia on: American-made vehicles (especially older Ford, Chev, Dodge — anything pre-metric conversion) Industrial machinery imported from the US Aerospace and marine applications (UNF dominates here) Some Australian-made gear that originally used Whitworth and converted to UN-series rather than metric UNC and UNF Sizes — Side by Side Nominal Size UNC TPI UNF TPI UNC Tap Drill (mm) UNF Tap Drill (mm) #6 32 40 2.85 2.95 #8 32 36 3.5 3.5 #10 24 32 3.9 4.1 1/4" 20 28 5.1 5.5 5/16" 18 24 6.5 6.9 3/8" 16 24 7.9 8.5 7/16" 14 20 9.4 9.9 1/2" 13 20 10.8 11.5 9/16" 12 18 12.2 13.0 5/8" 11 18 13.5 14.5 3/4" 10 16 16.5 17.5 7/8" 9 14 19.5 20.4 1" 8 12 22.25 23.25 When to choose UNC: general engineering, structural fastening, applications where you want fast assembly with hand tools. When to choose UNF: precision applications, thin-walled materials (more thread engagement per length), vibration-prone joints (the finer pitch resists self-loosening better), aerospace, motorsport. You cannot mix UNC and UNF at the same nominal size — a 1/2"-13 UNC bolt will not thread into a 1/2"-20 UNF nut, even though both are "imperial 1/2 inch". The pitch difference is the showstopper. BSW — British Standard Whitworth BSW (British Standard Whitworth) is the original imperial fastener thread invented by Joseph Whitworth in 1841. It uses the same 55° rounded thread form as BSP, but on solid fastener stock (not pipe). Defined by BS 84. You'll encounter BSW on: Pre-1970s Australian-made machinery — particularly Holdens, agricultural gear, and industrial plant Older British vehicles (Land Rover, BMC, Leyland, MG, etc.) Vintage tools and woodworking equipment Some legacy mining and railway equipment in Australia BSW is technically obsolete for new manufacturing — Australian industry transitioned to metric (and partly to UN-series) through the 1970s — but the legacy installed base is enormous. If you maintain old equipment in Australia, you'll meet BSW. Common BSW Sizes Nominal Size BSW TPI Pitch (mm) Tap Drill (mm) 1/8" 40 0.635 2.6 3/16" 24 1.058 3.7 1/4" 20 1.270 5.1 5/16" 18 1.411 6.5 3/8" 16 1.588 7.9 1/2" 12 2.117 10.5 5/8" 11 2.309 13.5 3/4" 10 2.540 16.5 1" 8 3.175 22.25 BSW vs UNC trap: 1/4"-20 BSW and 1/4"-20 UNC both have 20 threads per inch at 1/4" nominal — but the thread angle is different (55° vs 60°), so they don't mesh cleanly. Forcing them will work for a few turns, then bind or cross-thread. Metric M-Series Threads The metric M-series is the default thread standard for all new Australian manufacturing and most imported equipment. If the machinery was built after 1970, the fasteners are almost certainly metric unless it originates from the USA or is specifically identified as imperial. Metric threads use a 60° symmetric thread form (same angle as UNC/UNF) with flat crests and rounded roots. They are specified by nominal diameter in millimetres, followed by pitch in millimetres: M10 × 1.5 means 10mm nominal diameter, 1.5mm pitch (distance between thread crests). The governing standards are: ISO 68-1:2023 — general metric screw thread profile (the fundamental standard, now in its 2nd edition) ISO 261:1998 — metric screw thread general purpose sizes (the selection standard for preferred M-series sizes) ISO 262:1998 — selected metric screw thread sizes for screws, bolts and nuts AS 1275-1985 (reconfirmed 2017) — Australian adoption of the metric thread standard Metric Coarse (Preferred) Pitch — M3 to M30 Metric coarse pitch is the default — if a size is not marked as "fine" (F), assume coarse. Coarse pitch is faster to assemble, more tolerant of debris, and the correct choice for most general engineering applications. Size Coarse Pitch (mm) Tap Drill (mm) Minor Dia (mm) Common Application M3 0.5 2.5 2.459 Electronics, small instruments M4 0.7 3.3 3.242 Light machinery, switchgear M5 0.8 4.2 4.134 General engineering M6 1.0 5.0 4.917 Most common small fastener in AU workshops M8 1.25 6.8 6.647 Structural, automotive, machinery M10 1.5 8.5 8.376 Most common medium fastener M12 1.75 10.2 10.106 Structural steel, flanges M14 2.0 12.0 11.835 Automotive (cylinder head bolts) M16 2.0 14.0 13.835 Heavy structural, machinery bases M20 2.5 17.5 17.294 Foundation bolts, large structural connections M24 3.0 21.0 20.752 Large machinery, bridge structural M30 3.5 26.5 26.211 Heavy plant, foundation anchors Tap drill formula: Tap Drill = Nominal Diameter − Pitch (e.g. M10 × 1.5: tap drill = 10 − 1.5 = 8.5mm). This formula gives you 100% thread depth — in practice, 75% thread depth (drill slightly larger) is often preferred for easier tapping without significant strength loss. Metric Fine Pitch Metric fine pitch threads have smaller pitch at the same nominal diameter. For example, M10 × 1.25 (fine) vs M10 × 1.5 (coarse). Use metric fine where: Thin-walled components need maximum thread engagement per unit length Vibration resistance is required (finer pitch resists self-loosening) Precision adjustment is needed (e.g. bearing pre-load nuts, lock nuts on bearing housings) High-strength fasteners in automotive or motorsport applications Common metric fine sizes you'll encounter in Australian workshops: M8 × 1.0, M10 × 1.25, M12 × 1.25, M14 × 1.5, M16 × 1.5, M20 × 1.5. Metric vs Imperial — Quick Identification When you have an unknown fastener and need to determine metric or imperial quickly: Measure the pitch with a thread pitch gauge. If the pitch is a nice round millimetre number (1.0, 1.25, 1.5, 1.75, 2.0mm), it's metric. If it matches a TPI value (e.g. 20, 18, 16, 13 threads per inch), it's imperial. Measure the OD. Metric ODs are whole millimetre numbers (M8 OD = 8.0mm, M10 OD = 10.0mm, M12 OD = 12.0mm). Imperial ODs convert awkwardly (1/2" = 12.7mm, 5/8" = 15.875mm). Check the head markings. Metric grade marks are numbers (8.8, 10.9, 12.9). Imperial grade marks are lines (SAE Grade 5 = 3 lines, Grade 8 = 6 lines). For tap drill sizes across the full metric and imperial range, see our Tap Drill Size Chart (Metric & Imperial). For metric fastener size and grade references, see our Metric Bolt Size Guide. BSF — British Standard Fine BSF (British Standard Fine) is the fine-pitch companion to BSW, defined in BS 84:1956. It uses the identical 55° Whitworth rounded thread form as BSW, but with a finer pitch at each nominal size. BSF was widely used in British precision engineering applications from the early 1900s until metrication in the 1970s. You'll encounter BSF on: Pre-1970s British vehicle engines — many Jaguar, Rolls-Royce, Triumph, Rover and Leyland engines used BSF for cylinder head studs, cam covers and precision internal fittings where BSW's coarser pitch was considered inadequate British-made aircraft and aviation ground support equipment from the pre-metric era (the aviation industry was a major BSF user) Precision instruments, optical equipment and scientific apparatus manufactured in the UK pre-1970 Some legacy Australian-made machinery that followed British engineering practice BSF is technically obsolete for new manufacturing — there are no active orders or new stock being produced in BSF. Maintenance and restoration of legacy equipment are the only reasons to source BSF fasteners today. BSW vs BSF — Side by Side Nominal Size BSW TPI BSF TPI BSW Tap Drill (mm) BSF Tap Drill (mm) 1/4" 20 26 5.1 5.5 5/16" 18 22 6.5 6.8 3/8" 16 20 7.9 8.3 7/16" 14 18 9.4 9.7 1/2" 12 16 10.5 11.1 9/16" 12 16 11.9 12.5 5/8" 11 14 13.5 14.0 3/4" 10 12 16.5 17.0 1" 8 10 22.25 22.75 Identification tip: BSF and BSW share the same thread angle (55°) and the same nominal sizes. The ONLY reliable way to distinguish them is to count TPI with a thread pitch gauge. A 1/2" thread with 12 TPI is BSW; a 1/2" thread with 16 TPI is BSF. Visually, BSF threads appear finer (closer-spaced crests). Do not attempt to determine this by eye alone. For imperial tap and die sets covering BSW and BSF, see our Imperial Hand Taps collection. ACME and Trapezoidal Threads ACME and Trapezoidal threads are power transmission threads, not fastener threads. Instead of clamping two components together, they convert rotational motion into linear motion — in lead screws, lathes, vices, jacks, valve stems and linear actuators. They look completely different from standard fastener or pipe threads and are very unlikely to be confused with them once you know what to look for. ACME Threads (Imperial) ACME threads are governed by ASME B1.5-1997 (reaffirmed 2024). They use a distinctive 29° thread form (14.5° each side from the thread centreline), producing a wide, flat-topped, visible tooth. ACME is the standard power screw thread used in American and Australian-origin lathes, milling machines, toolroom vices, and lifting jacks. Key ACME characteristics: 29° included thread angle — immediately visible as a wider tooth than fastener threads NOT self-locking — a loaded ACME screw will back-drive under load unless a separate brake or lock is fitted. This is a critical safety consideration for vertical lifting applications Specified as: diameter × pitch in TPI (e.g. 3/4-6 ACME = 3/4 inch diameter, 6 threads per inch) Available in General Purpose (G) and Centralising (C) classes — General Purpose is the workshop standard ACME Size Reference Diameter TPI (Coarse) Pitch (mm equiv.) Typical Application 1/4" 16 1.59 Small instrument screws 5/16" 14 1.81 Light jigs and fixtures 3/8" 12 2.12 Small vice screws 1/2" 10 2.54 Medium vice, clamps 5/8" 8 3.18 Lathe cross-slide screws 3/4" 6 4.23 Lathe lead screws, jack screws 1" 5 5.08 Large vice screws, lifting gear 1-1/4" 5 5.08 Heavy lathe bed traverses 1-1/2" 4 6.35 Screw presses, heavy lifting 2" 4 6.35 Large screw jacks, arbor presses Trapezoidal (Tr) Threads — The Metric Equivalent The metric equivalent of ACME is the Trapezoidal thread, designated as Tr and standardised in ISO 2901–2904. The thread form is similar in purpose to ACME but uses a 30° included thread angle (slightly steeper flanks than ACME's 29°) and metric sizing. For example: Tr 20 × 4 = 20mm diameter, 4mm pitch. Feature ACME Trapezoidal (Tr) Standard ASME B1.5-1997 (R2024) ISO 2901–2904 Thread angle 29° 30° Sizing system Imperial (inches, TPI) Metric (mm diameter × mm pitch) Interchange NOT interchangeable — different angle + different sizing system Common on US/AU-origin lathes, vices, jacks European CNC machines, metric lead screws Self-locking? No No Identification: Both ACME and Tr threads are immediately recognisable by their wide, flat-topped tooth profile. If the machine is marked in imperial, it's ACME. If metric, it's Tr. Do not attempt to use ACME taps or dies on a Tr screw — the 1° angle difference and metric pitch will destroy the thread. Thread Selection Guide — Which Standard for Your Application? Choose the right thread standard before you cut, tap or order. Retrofitting is expensive. Application Correct Standard Reason New Australian manufacturing — any fastener Metric M-series (coarse) AS 1275 default; off-the-shelf stock widely available Hydraulic and compressed-air fittings in AU BSP (BSPP or BSPT) Australian/Commonwealth default for fluid systems Plumbing — water and gas BSPT Tapered thread self-seals with PTFE tape US-import equipment fitting or repair NPT American equipment default for pipe threads US-import fasteners or machinery repair UNC (general) or UNF (precision) American fastener standard; match existing thread standard Pre-1970s Australian/British machinery repair BSW (general) or BSF (precision) Match existing thread; check with pitch gauge first Lathe, vice, jack or linear actuator lead screw ACME (imperial) or Tr (metric) Power transmission thread; match the machine's original spec High-vibration or thin-wall precision fastening Metric fine or UNF Finer pitch = better vibration resistance and thread engagement How to Identify a Thread by Sight (and Three Tools That Help) If you've inherited a fitting with no markings and need to know what it is, work through this checklist: Pipe or fastener? If it has a bore (it's hollow), it's almost certainly a pipe thread — BSP or NPT. If it's a solid stud, bolt or screw, it's a fastener thread — UNC, UNF, BSW, or metric M-series. Tapered or parallel? Run a straight edge along the thread. If the OD reduces as you move along the thread, it's tapered (BSPT or NPT). If it's straight, it's parallel (BSPP, UNC, UNF, BSW, M). Check the thread angle with a thread angle gauge. 55° = British heritage (BSP, BSW). 60° = American or metric (NPT, UNC, UNF, M). Measure the pitch with a thread pitch gauge. Compare against the size tables above to confirm the standard. Measure the OD with calipers and cross-reference against the relevant table. The three tools that make this fast: Thread pitch gauge (metric and imperial blade sets) — slide each blade against the thread until one matches Caliper — measure the male OD Thread identification chart — laminated reference card with the common sizes (you've effectively got one above) See our Screw Pitch Gauges collection for thread identification gauges. Are BSP and NPT Interchangeable? (No — Here's Why) No. BSP and NPT are not interchangeable, even though they share several nominal sizes and the same 1:16 taper on the tapered variants. The reasons they don't mesh: Thread angle differs. BSP is 55°, NPT is 60°. The peaks and valleys of the threads have different geometry, so even when they bind for a few turns, only the very tips of the threads contact — there's no real engagement to seal against. TPI is different at most sizes. 1/8" BSP is 28 TPI; 1/8" NPT is 27 TPI. 1/4" BSP is 19 TPI; 1/4" NPT is 18 TPI. 1" BSP is 11 TPI; 1" NPT is 11.5 TPI. The pitch mismatch compounds with the angle mismatch. The thread form differs. BSP has rounded crests and roots (Whitworth form). NPT has flat crests and rounded roots. Even where the angle and TPI happen to match, the form difference means partial-only engagement. The only sizes where BSP and NPT share both TPI AND nominal size are 1/2" and 3/4" (both 14 TPI). At these sizes you'll get further before the angle mismatch reveals itself — which is exactly why these sizes cause the most cross-thread damage in workshops. Always identify the standard before assembly. Don't trust "looks close enough". Sealing Tapered vs Parallel Threads How you seal a thread depends on whether it's tapered or parallel — and getting this wrong is one of the most common causes of leaking fittings in industrial workshops. Tapered threads (BSPT, NPT) The metal-to-metal taper IS the seal. As you tighten, the male wedges into the female and the threads deform slightly to fill voids. PTFE tape (typically 3-5 wraps in the direction of thread engagement) or a thread sealant like Loctite 567 / 577 fills micro-voids and stops capillary leaks, but the seal is fundamentally mechanical. Tradesperson rules: Wind PTFE tape clockwise looking down the male thread (so tightening winds the tape on, not off) Don't apply tape to the first thread — leave it bare to avoid tape entering the system Hand-tight + 1-2 wrench turns is usually enough; over-tightening cracks fittings Liquid sealants like Loctite 577 are often preferred over PTFE for hydraulic applications because they don't shred Parallel threads (BSPP, UNC, UNF, metric) The thread itself does NOT seal. You need a separate sealing element: Bonded seal washer (Dowty) — under the fitting head, the rubber bond compresses against a flat seat O-ring — seated in a port face groove or against a flat sealing face Copper/aluminium crush washer — single-use, deforms to seal Flat fibre or rubber washer — for lower-pressure applications Wrapping PTFE tape around a BSPP male thread and screwing it into a BSPP port without a Dowty or O-ring is a leak waiting to happen. The threads simply do not have the geometry to seal themselves. For sealing products see our Thread Sealants collection. Common Conversion Mistakes That Destroy Fittings The most expensive errors we see at AIMS Industrial — collected from years of customer calls: BSP male into NPT female on imported hydraulic gear. Customer assumes the fitting is BSP because it looks like all the others; equipment is American and the port is NPT. After 3 turns it binds. Customer tightens harder. The casting cracks. Replacement pump housing: $400-2,000. NPT male into BSP female on Aussie plumbing. Reverse of above. Common with imported pneumatic tools forced onto BSP shop air lines. Slight angle mismatch means it leaks under pressure no matter how much PTFE tape you wrap. BSPP forced into BSPT (or vice versa) without realising the receiver is the other one. Same nominal size, same 55° angle, same TPI — but one is parallel and one is tapered. Parallel-into-tapered won't reach full engagement. Tapered-into-parallel won't seal because nothing wedges. UNC bolt into UNF nut. Same nominal diameter, same 60° angle, different TPI. The bolt will start, then bind or strip the nut after a few turns. 1/4" BSW bolt into 1/4" UNC nut. Same TPI (both 20), same nominal size, different angle (55° vs 60°). Forces will work but the joint has only partial thread engagement and minimal preload capacity. Common on classic-vehicle restorations. M10 bolt into 3/8" UNC hole. Nearly the same nominal diameter (10mm vs 9.525mm), different angle (60° matches but pitches don't — 1.5mm vs 1.59mm). Will bind partway in. The fix for all of these: identify before you tighten. A 30-second check with a thread pitch gauge prevents a $400 mistake. Tools You Need to Get Thread Identification Right The basic tradie kit for any workshop dealing with multiple thread standards: Thread pitch gauge (metric and imperial sets) — see Screw Pitch Gauges Caliper for measuring OD and pitch diameter Tap and die set covering the standards you work with — see Taps, Imperial Hand Taps, Metric Spiral Point Taps Pipe dies for the pipe standards you encounter — see Dieheads for Pipe Machines Thread sealants — see Thread Sealants AIMS Thread-Standard Product Cross-Reference Sourcing fittings and tools for each standard from AIMS Industrial: BSP fittings: Brass Fittings, Iron Pipe Fittings, Pipe Fittings, Hose Fittings & Couplings Imperial taps (UNC / UNF / BSW / BSP): Imperial Hand Taps, Imperial Spiral Flute Taps Metric taps: Metric Spiral Point Taps Stainless fasteners (UNC, UNF, metric): Stainless Fasteners Thread identification: Screw Pitch Gauges Thread sealants: Thread Sealants Full threading range: Threading Collection Sutton Tools (Australian-made cutting tools): Sutton Tools Related Reference Articles Tap Drill Size Chart — Metric & Imperial (the size data behind this article) Metric vs Imperial Fastener Reference Guide Drill Bit Size Chart — Metric, Imperial, Fractional Metric Bolt Size Guide Loctite 577 Pipe Sealant Guide Spiral Wound Gasket Guide Frequently Asked Questions What is BSP thread? BSP (British Standard Pipe) is the dominant pipe thread standard in Australia, the UK and Europe. It uses a 55° rounded Whitworth thread form. There are two variants: BSPP (parallel — needs a separate seal) and BSPT (tapered — seals via metal-to-metal interference). Defined by ISO 228 (BSPP) and ISO 7-1 (BSPT). What is NPT thread? NPT (National Pipe Taper) is the American pipe thread standard, governed by ANSI/ASME B1.20.1. It uses a 60° symmetric thread form on a 1:16 taper. The thread self-seals via the taper. You'll see NPT in Australia mostly on US-imported equipment — compressors, hydraulic pumps, pneumatic tools. What is the difference between BSP and NPT? BSP and NPT differ in three critical ways: thread angle (BSP is 55°, NPT is 60°), thread form (BSP has rounded crests, NPT has flat crests), and pitch (TPI differs at most nominal sizes). They are not interchangeable, even where they share a nominal size. Forcing one into the other will cross-thread, leak, or crack the fitting. Is BSP the same as NPT? No. BSP and NPT share neither thread angle, thread form, nor TPI at most sizes. They look similar because they share the 1:16 taper on the tapered variants (BSPT and NPT). The visual similarity is the cause of most cross-threading damage in Australian workshops. What is the difference between BSPP and BSPT? BSPP (Parallel) and BSPT (Tapered) share the same 55° Whitworth thread form, the same TPI, and the same nominal sizes. The difference is the thread profile along the pipe length: BSPP runs straight, BSPT runs on a 1:16 taper. BSPP needs a separate seal (bonded washer, O-ring); BSPT self-seals via the taper plus PTFE tape or thread sealant. How do I identify a BSP thread? Use a thread pitch gauge to measure pitch and a 55° thread angle gauge. A 1/2" BSP male thread has an OD of approximately 21mm and 14 TPI — matching neither metric M-series nor any UN-series fastener at 1/2" nominal size. If the OD is significantly larger than the nominal size suggests, you're probably looking at a BSP pipe thread. How do I identify an NPT thread? Same process as BSP — pitch gauge, thread angle gauge — but you're looking for a 60° angle (NPT specific) and a tapered profile. 1/2" NPT is 14 TPI with a male OD of about 21.2mm at the gauge plane. Compare against the NPT table in this article. Note: NPT and BSPT at 1/2" share TPI (both 14) — distinguish by thread angle (60° vs 55°) and the slightly larger NPT OD. What is UNC thread? UNC (Unified National Coarse) is the American imperial fastener thread standard for general-purpose work. It uses a 60° symmetric thread form. Example: 1/2"-13 UNC means 1/2 inch nominal diameter, 13 threads per inch. Defined by ANSI/ASME B1.1. What is UNF thread? UNF (Unified National Fine) is the fine-pitch counterpart to UNC. Same 60° thread form, but more threads per inch — for example 1/2"-20 UNF has 20 TPI (compared to 13 TPI for 1/2" UNC). Used where precision, vibration resistance or thin-wall thread engagement matters: aerospace, motorsport, hydraulic fittings. What is the difference between UNC and UNF? UNC has fewer threads per inch (coarser pitch); UNF has more threads per inch (finer pitch). UNC is faster to assemble and more tolerant of dirty conditions. UNF gives finer adjustability, better vibration resistance and more thread engagement per length of thread. They are not interchangeable at the same nominal size. Is BSW the same as BSP? No, but they share the 55° Whitworth thread form. BSW (British Standard Whitworth) is a fastener thread standard. BSP (British Standard Pipe) is a pipe thread standard. The sizing conventions and applications are different. BSW is for bolts and studs; BSP is for fittings on pipes and bores. Can I screw a BSP fitting into an NPT thread? You can start it, but you should not commit to it. BSP and NPT have different thread angles (55° vs 60°), different TPIs at most sizes, and different thread forms. The fit will be partial, the seal will leak under pressure, and over-tightening to force a seal will crack the casting. Use the correct standard for the receiving thread — always. What sealant should I use on BSPT threads? BSPT is a tapered thread that self-seals. PTFE tape (3-5 wraps clockwise looking at the male thread, leaving the first thread bare) is the common workshop choice. For hydraulic applications, liquid sealants like Loctite 567 or Loctite 577 are often preferred because they don't shred under high pressure. Don't over-wrap — excess tape can split fittings. What sealant should I use on BSPP threads? BSPP is parallel — the thread itself does not seal. You need a separate sealing element such as a bonded seal washer (Dowty), an O-ring seated in a port face, or a copper crush washer. Wrapping PTFE tape on a BSPP male and trying to seal it is a common mistake; it will leak under pressure because the thread provides no wedging action. How can I tell if a thread is metric or imperial? Measure the pitch with a thread pitch gauge. Imperial threads are specified in TPI (threads per inch); metric threads are specified in mm pitch. If your gauge blades match a metric pitch (0.5, 0.75, 1.0, 1.25, 1.5, 1.75, 2.0, 2.5, 3.0mm), it's metric. If they match a TPI value (16, 18, 20, 24, 28 etc.), it's imperial. The 60° vs 55° angle test also helps — metric is always 60°, BSP and BSW are 55°. Why do BSP and NPT both use a 1:16 taper? The 1:16 taper (3/4 inch reduction per foot of length) was chosen independently by both standards because it gives a good balance of thread engagement and sealing force without requiring excessive turns to tighten. The shared taper is the reason BSPT and NPT look similar at a glance — but the underlying thread angles (55° vs 60°) make them mechanically incompatible. Cross-reference our Tap Types guide when picking between taper, plug, bottoming, gun and spiral flute taps.People Also Ask — Thread Identification Q: How do I identify an unknown thread without a gauge? Without a thread pitch gauge, start with the basics: check if the thread is on a pipe/bore (likely BSP or NPT) or a solid fastener (metric, UNC/UNF, BSW/BSF). Then look at the thread angle visually — 55° threads have noticeably rounded crests and a gentler profile compared to 60° threads. Count the number of thread crests visible over a 25mm (1 inch) length using a ruler to estimate TPI. Compare against the size tables in this guide. A proper thread pitch gauge is a $30–50 investment that pays for itself on the first identification job — see our Screw Pitch Gauges collection. Q: What is the main difference between metric and imperial threads? The main differences are sizing convention and pitch specification. Metric threads are specified by diameter in millimetres and pitch in millimetres (M10 × 1.5 = 10mm diameter, 1.5mm between crests). Imperial threads are specified by diameter in fractions of an inch and pitch in TPI — threads per inch (1/2"-13 UNC = 1/2 inch diameter, 13 threads per inch). Both metric and UNC/UNF use a 60° thread form, so angle alone won't distinguish them. You need the pitch gauge and calipers. A 10mm diameter is metric; 3/8" (9.525mm) is the nearest imperial equivalent — and the pitches don't match. Q: Can I use a metric bolt in an imperial nut? No — not reliably. While some metric and imperial sizes are close in diameter, the pitch (thread spacing) doesn't match. For example, M10 × 1.5 and 3/8"-16 UNC have similar diameters (10mm vs 9.53mm) but different pitches (1.5mm metric vs 1.59mm imperial). They'll start but bind partway in, and any force will strip the nut. The one-turn rule applies: if a bolt doesn't thread in cleanly by hand for at least 3–4 turns, it's the wrong thread. Never use a wrench to force a thread that won't start cleanly by hand. Q: What thread standard do Australian plumbers and hydraulic fitters use? Australian plumbers and hydraulic fitters use BSP (British Standard Pipe) as the default. BSPT (tapered) is used for water, gas and most pressure fittings where the thread itself creates the seal. BSPP (parallel) is used for hydraulic systems where an O-ring or bonded seal provides the sealing function. You'll only encounter NPT on US-imported equipment — it is not the Australian default and is not used in domestic plumbing. If you're buying fittings from an Australian supplier for an Australian installation, specify BSP unless the existing fittings are confirmed NPT. Q: What is the difference between BSF and BSW threads? BSF (British Standard Fine) and BSW (British Standard Whitworth) share the same 55° Whitworth thread form and nominal size range, but BSF has more threads per inch at each size. For example, 1/2" BSW is 12 TPI and 1/2" BSF is 16 TPI. They are not interchangeable at the same nominal size. BSW was used for general structural fastening; BSF was used where vibration resistance or precision was required — engine internals, aviation hardware, precision instruments. Both are obsolete for new manufacturing. Identify which you have using a thread pitch gauge before ordering replacement fasteners. People Also Ask — Thread Identification — BSP, NPT, Metric & More Q: What is the difference between BSP and NPT threads? BSP (British Standard Pipe) uses a 55° thread angle with a parallel thread form in the most common variant (BSPP), while NPT (National Pipe Taper) uses a 60° thread angle with a tapered thread that self-seals. The two standards are not interchangeable — forcing a BSP fitting into an NPT port risks cross-threading and leaks even when the threads initially appear to engage. Q: How do I identify a thread type without gauges? Measure the thread pitch (distance between crests) with a thread pitch gauge or by counting threads over a known length, then measure the outside diameter. Compare these values against size charts for BSP, NPT, and metric. The thread angle — 55° for BSP and Whitworth, 60° for NPT, UNC, and metric — also helps distinguish families, though a profile gauge makes this faster and more reliable. Q: Can BSP and NPT fittings be mixed? No. BSP and NPT fittings appear similar in some sizes and have nearly identical thread counts in certain dimensions, but the different thread angles (55° vs 60°) and pitch values mean they will not seal correctly together. Using a BSPP fitting in an NPT port, or vice versa, typically produces a leak-prone connection even when it initially feels tight. Q: What does BSPP mean compared to BSPT? BSPP is British Standard Pipe Parallel — the thread maintains the same diameter along its length and relies on a face seal or O-ring for sealing. BSPT is British Standard Pipe Taper — the thread tapers and the taper itself creates a seal in conjunction with PTFE tape or thread sealant. Most hydraulic and pneumatic systems use BSPP with an O-ring face seal. Q: How do I measure thread pitch? For metric threads, pitch is measured directly as the distance between adjacent crests in millimetres. For imperial threads (BSP, NPT, UNC), pitch is expressed as threads per inch (TPI) — count the crests over one inch of thread length. Thread pitch gauges are the fastest and most reliable method, with common sets covering both metric and imperial standards. Browse metric thread forming taps at AIMS Industrial for application support and stock confirmation. AIMS Industrial stocks taper pipe reamers — see the full range for trade and industrial use.
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Choosing the Right Drill Bit: Types, Sizes & Charts
10 Quick Tips in Selecting the Right Drill Bit: Material Type: Choose bits designed for wood, metal, plastic, or masonry. Drill Bit Gauge: Use a gauge to identify bit sizes quickly. Screw Match: Match the bit to the screw's shank diameter. Size Charts: Cross-reference metric and imperial sizes. Test First: Test on scrap material before the final piece. Bit Labels: Ensure bits are clearly labeled for easy identification. Pilot Holes: Use smaller bits for pilot holes to prevent splitting. Speed Settings: Adjust drill speed based on bit size and material. Bit Quality: Invest in high-quality bits for better performance. Storage: Keep bits organized in a labeled case or holder. Why Drill Bit Sizes Matter Picking the right drill bit size ensures your screws and bolts fit perfectly, preventing damage to your workpiece and the drill bit. Metric vs. Imperial: The Basics Metric sizes are in millimeters, while imperial sizes are in inches. For example, a 10mm drill bit is roughly the same as a 3/8 inch bit. Knowing these conversions can save you a lot of frustration, especially when working with imported tools and materials. Must-Have Bit Sets for Your Toolbox Whether your are just starting or replenishing, these are our must-have sets to consider: Metric Drill Bit Set Imperial Drill Bit Set Countersink Bits Panel Drill Bit sets Sutton Tools Long Series Drill Bits These sets can cover all your initial drilling needs, ensuring you always have the right tool for the job. CLICK TO DOWNLOAD OUR FREE PRINTABLE DRILL BIT SIZE CHART PRO TIP: You can also buy a Sutton M8100650 Metric and Imperial Multi Function Gauge to measure your drill bits, fasteners, nuts and threads. Extra FREE CHARTS below: Anchor Bolt Size Chart: Find metric anchor bolts like countersunk head, drop-in, hex flange nut, flush head, and stud anchors. Common diameters included. Fastener Reference Chart: Cross-reference bolt, nut, or screw sizes with metric, Unified Thread Standard, and British Thread Standards. Simple illustrations included. Loctite Application Chart: Choose the right Loctite product for various materials and surfaces. Pulley Size Chart: Browse aluminum and cast-iron pulleys for different belt sections and grooves. Metric and imperial sizes available. Socket Sizing Cross-Reference Chart (Metric-Imperial Values): Match sockets and drives in metric and imperial sizes. Spanner Size Chart: Find the right spanner size for hexagonal bolts, nuts, or screws. Metric and imperial sizes included. Tapping Drill Size Chart for Thread Cutting Taps: Identify the right drill size for pilot holes before cutting threads. Metric and imperial sizes included. No matter the project, choosing the correct drill bit size is crucial for achieving cleaner, more precise holes. Not only does it enhance the quality of your work, but it also extends the life of your tools and materials. By investing a little time in selecting the right bit, you can ensure professional results and avoid unnecessary wear and tear. Browse the AIMS Carbide Drill Bits range — solid carbide and tungsten carbide tipped, in metric and imperial sizes. People Also Ask — Choosing Drill Bits Q: What drill bit should I use for stainless steel? Stainless steel requires a drill bit with high heat resistance and edge toughness. Cobalt drill bits (HSS-Co, typically 5% or 8% cobalt) are the standard choice — the cobalt content raises the bit's resistance to the work-hardening effect that stainless produces under heat and friction. Use cutting fluid, reduce spindle speed compared to mild steel by 30–50%, and use moderate feed pressure to prevent the work-hardening effect. Solid carbide drills provide the highest performance in stainless in production environments but require a rigid, vibration-free setup. Q: What is the difference between HSS and carbide drill bits? High-speed steel (HSS) drill bits are tough, less brittle, and tolerant of slight misalignment — suitable for general workshop use on steel, aluminium, and plastics. Carbide drill bits (solid carbide or carbide-tipped) are significantly harder than HSS, hold their cutting edge longer, and can run at higher speeds — but they are brittle and require a rigid machine setup with minimal runout. HSS is typically the right choice for hand drills and flexible setups; carbide is the right choice for CNC machining centres, vertical mills, and dedicated drilling machines where rigidity is assured. Q: How do I select the right drill bit size for a tapped hole? The correct tap drill size depends on the thread standard and the required percentage of thread engagement. For metric coarse threads, a common rule is: tap drill diameter (mm) = nominal diameter (mm) − pitch (mm). For example, M8 × 1.25 → 8 − 1.25 = 6.75mm tap drill (often rounded to 6.8mm for 75% thread engagement). Use the tap drill size charts in the AIMS threading guide for precise recommendations across metric coarse, metric fine, UNC, UNF, and BSP thread series. Q: Why do my drill bits keep breaking when I drill metal? Drill bit breakage in metal most commonly results from: (1) excessive feed pressure — forcing the bit rather than letting the cutting edges do the work; (2) running at too-high a speed for the material — raises heat, softens the cutting edge; (3) running at too-low a speed — reduces chip evacuation, increases torque on the bit; (4) inadequate cutting fluid — causes overheating and welding of chips to the cutting edge; (5) a dull bit — a sharp drill requires far less force and runs cooler. Always use cutting fluid on steel and stainless, and check your speed and feed against the recommended values for the bit diameter and material. Q: What drill bit is best for drilling into concrete or masonry? Masonry drill bits have a carbide-tipped cutting edge brazed to a steel shank, designed for use in a hammer drill or SDS rotary hammer. The percussion action of the drill fractures the aggregate while the carbide tip clears the dust. For SDS drills, use SDS-Plus or SDS-Max bits matched to the drill's chuck type. Do not use standard HSS drill bits on concrete or masonry — they will blunt immediately. For very hard stone or reinforced concrete, diamond-tipped core drills may be required for large diameter holes. AIMS Industrial stocks long drill bits — see the full range for trade and industrial use.
Read moreTeflon (PTFE) Spray Guide: Dry-Film Lubricant Uses, Applications and Mistakes
Teflon spray (PTFE spray) is a dry-film lubricant — slippery, dust-rejecting, ideal for tracks, locks, sliding rails and treadmill belts. Forum-validated guide covering wet vs dry PTFE, when it wins over silicone/grease, lock and bike-chain debates, treadmill warnings, NSF H1 food-grade applications, and the real reasons it sometimes attracts dust. CRC range stocked at AIMS Industrial.
Read moreDowty Washer Guide: Bonded Seals for Hydraulic & BSP Fittings
A Dowty washer — also called a bonded seal washer — is a metal washer with a vulcanised rubber ring bonded permanently to its inner bore. When the fitting is tightened, the rubber compresses against a flat machined face and forms a leak-tight static face seal. The metal washer acts as a hard stop, limiting how far the rubber is squashed and giving a controlled, repeatable seal. Standard on BSP parallel ports, hydraulic adapters, fuel and lubrication unions, gauge ports and instrumentation. They only work on parallel-thread fittings — never on tapered thread. BSP / Metric Size Bore (mm) Outer Dia (mm) Rubber Typical Fitting 1/8" BSPP / M10 10.0 15.0 NBR Gauge ports, instrumentation 1/4" BSPP / M14 13.7 20.0 NBR Pneumatic fittings, small hydraulic ports 3/8" BSPP / M18 17.3 23.7 NBR Hydraulic adapters, lubrication banjos 1/2" BSPP / M22 21.6 28.5 NBR Hydraulic hose tails, fuel unions 3/4" BSPP / M27 27.0 34.0 NBR Larger hydraulic ports, pump fittings 1" BSPP / M33 33.7 41.5 NBR Heavy hydraulic, drain plugs Nominal sizes — outer diameter varies slightly between manufacturers. Always check the fitting drawing if there's a tight spotface. What Is a Dowty Washer "Dowty washer" started life as a brand name. Dowty Seals Ltd, a British engineering firm founded by Sir George Dowty, patented the bonded seal washer design in the 1940s and became the dominant supplier through the post-war hydraulic boom — particularly for British military aviation hydraulics running at 3,000 psi. The name stuck. Today the company is part of GKN Aerospace, the patent has long expired, and dozens of manufacturers — Hutchinson, Trelleborg, Garlock, James Walker and a long tail of generic suppliers — produce the same design. The generic engineering term is bonded seal washer (sometimes self-centring washer or self-sealing washer), but tradies and parts catalogues across Australia still call them Dowty washers. The design solves a specific problem: how to seal a bolted joint or threaded fitting reliably without thread tape, anaerobic sealant or a separate O-ring groove. The bonded seal does it in one part — a stamped metal washer with rubber moulded and vulcanised directly to its inner edge. Drop it under the bolt head or fitting shoulder, tighten to spec, and the rubber compresses to form a face seal against the mating surface. No mess, no cure time, no thread prep. How a Bonded Seal Works — the Controlled-Compression Principle The mechanics are straightforward. The metal washer carries the bolt clamping load — the same as a flat washer would. The rubber ring bonded to the inner bore sits proud of the metal washer's face by a controlled amount (typically 0.3–0.6 mm) when uncompressed. When the bolt or fitting is tightened, three things happen in sequence: The rubber contacts the mating face first and starts to compress before the metal washer is fully seated. The rubber deforms radially into the gap between the bolt shank and the bolt hole, filling any micro-irregularities in the mating surface. The metal washer bottoms out against the mating face, stopping further rubber compression at the design value. The rubber is now squeezed to roughly 70–80% of its free height — enough to seal, not so much that it splits or extrudes. That last step is the clever bit. Without the metal washer acting as a hard stop, a torque-controlled assembly process would either under-squash the rubber (leak) or over-squash it (split, extrude, fail in a few months). The bonded seal is self-limiting by geometry, so it tolerates a wide range of installation torques without losing its seal — exactly what you want on a workshop floor where fitters use rattle guns and feel rather than calibrated torque wrenches. One consequence: the bond between rubber and metal is the most critical part of the washer. A cheaply made bonded seal where the rubber peels away from the metal under fluid pressure will fail in service even though the install torque was correct. This is why engineering-grade brands cost more than $0.20 generic eBay parts — the surface preparation, primer, vulcanisation cycle and quality control on the bond. The #1 Mistake — Parallel vs Tapered Thread ⚠️ The #1 cause of leaks — bonded seals do NOT work on tapered thread Consensus across r/AskEngineers, Practical Machinist hydraulics threads and tractor mechanic forums: bonded seal washers are designed to seal against a flat boss face on a parallel-thread fitting (BSPP / BSP-Parallel / M-Parallel / UN-Parallel). They will NOT seal a tapered-thread fitting (BSPT / NPT) because there is no flat face for the rubber to compress against. If you're trying to seal an NPT or BSPT fitting, use thread sealant (Loctite 567 / 577 / PTFE tape) — not a bonded seal. Mismatching the two is the most common source of leaks in DIY hydraulic and pneumatic installs. This is worth unpacking because it's so common. Australian industry runs almost exclusively on BSP, but there are two variants that look identical to the untrained eye and seal in completely different ways: BSPP (BSP Parallel, sometimes called BSP-G or just G thread) — same diameter all the way along the thread. Seals against a flat machined face at the bottom of the male thread or under the head — using a bonded seal washer, copper crush washer or O-ring. The thread itself does not seal. You can spin the male into the female by hand all the way home with no resistance. BSPT (BSP Tapered, sometimes called BSP-R or just R thread) — gets fatter as you go along the thread. Seals by metal-to-metal wedging of the male and female thread flanks. Needs thread sealant (PTFE tape, Loctite 567, Loctite 577) to fill the spiral leak path between the engaged threads. You feel the male tighten up halfway in — that's the taper engaging. NPT (American National Pipe Tapered) is similar to BSPT but with a different thread angle (60° vs BSPT's 55°), and the two are not interchangeable despite looking similar. How to spot the difference in the workshop: Take the fitting and try to thread the male into the female by hand. If it spins all the way home easily and stops at a flat shoulder — BSPP, use a bonded seal. If it tightens up partway in with no visible shoulder to seat against — BSPT or NPT, use thread sealant. If you put a bonded seal under a BSPT fitting, the rubber has nothing flat to compress against and the joint will weep oil within hours of pressurisation. Conversely, if you wrap PTFE tape on a BSPP fitting, the tape stops the bonded seal seating correctly and the joint will leak even though it feels tight. Forum reality check (Yesterday's Tractors, Practical Machinist threads on persistent BSP leaks): the second most common cause of BSP leaks after thread-type confusion is losing the bonded seal during disassembly. The rubber-bonded washer is small, dark and often stuck to the fitting shoulder by old oil. It can fall off into a drip tray during a service and get binned. Without it, a BSPP fitting cannot seal regardless of how tightly it's torqued — and the next mechanic to look at it spends an hour chasing a leak that's actually a missing $0.50 part. Always check the seal is there and replace it if there's any doubt. Rubber Materials — NBR, Viton/FKM, EPDM The metal washer is almost always carbon steel with a zinc-plated or zinc-and-clear-passivate finish. Stainless steel (304 or 316) is available for marine, food contact or aggressive chemical service. The metal selection is straightforward — match the bolt and fitting material to avoid galvanic corrosion in wet service. The rubber is where most of the selection thinking happens. Three compounds cover roughly 95% of Australian industrial use: Compound Temp Range Best For Avoid NBR (Nitrile / Buna-N) -30°C to +100°C Hydraulic oil, pneumatic air (dry or lubricated), diesel, petrol, mineral oils, general industrial Brake fluid (DOT 3/4/5.1), strong acids/caustics, ozone, sustained UV, ethanol-blend fuels (long-term) FKM (Viton / fluoroelastomer) -20°C to +200°C Hot oil, fuel including ethanol blends and E85, aggressive solvents, high-temperature hydraulic, automotive engine bay, refrigerant systems Brake fluid, ketones (MEK, acetone), hot water/steam, amines EPDM -40°C to +120°C Brake fluid (DOT 3/4/5.1), water-based hydraulics (HFC/HFA), hot water, steam, mild acids/caustics, ozone, outdoor exposure Mineral oil, petroleum products, hydraulic oil — EPDM swells and fails in minutes NBR is the default. Unless the application calls for something specific — hot oil, brake fluid, food contact, aggressive chemistry — assume NBR. AIMS stocks NBR bonded seals across the full BSP and metric range because that's what 90% of jobs need. Forum-validated compatibility traps: Ethanol-blend fuels (E10, E85) — automotive forums repeatedly flag NBR bonded seals failing within 12 months on ethanol-blend fuel lines. The ethanol leaches plasticisers out of the nitrile and the rubber hardens, shrinks and cracks. Use FKM (Viton) for any fuel system fitting that will see E10 or higher. Brake fluid — never NBR or FKM. DOT 3/4/5.1 fluids are glycol-based and chemically attack both. Use EPDM. DOT 5 (silicone-based) is the exception — silicone fluid is compatible with NBR. Mechanics regularly get caught out on this swap. Hot mineral oil >100°C — NBR hardens and cracks at sustained temps above 100°C. If the fitting is on an engine block or hydraulic return line near a heat source, step up to FKM. Refrigeration systems (HVAC) — refrigerant oils and HFC refrigerants need FKM. NBR will swell. Sizing — BSP, Metric, UNF Bonded seal washers are sized by the bolt or thread they fit, not by an arbitrary part number. The two dimensions that matter are the bore (must be a slip fit over the male thread) and the outer diameter (must fit within the spotface or counterbore on the female component). Thread Size Bore (mm) Outer Dia (mm) Thickness (mm) 1/8" BSPP / M10 10.0 15.0 1.5 1/4" BSPP / M14 13.7 20.0 1.5 3/8" BSPP / M18 17.3 23.7 1.5 1/2" BSPP / M22 21.6 28.5 2.0 5/8" BSPP / M24 23.5 31.0 2.0 3/4" BSPP / M27 27.0 34.0 2.0 1" BSPP / M33 33.7 41.5 2.5 1-1/4" BSPP / M42 42.0 50.5 2.5 1-1/2" BSPP / M48 48.5 56.5 2.5 2" BSPP / M60 60.5 69.0 3.0 Metric (M) and BSPP sizes overlap because most hydraulic and pneumatic component manufacturers use metric bolts with parallel-thread (M-Parallel) and the bonded seal range was sized to fit both standards. UNF sizes (1/4"-28, 5/16"-24, 3/8"-24 etc.) are stocked for older British and US-spec equipment but make up a small fraction of Australian industrial use. Common Applications Bonded seal washers turn up everywhere a flat-face seal is needed against a parallel-thread fitting or bolted joint: Hydraulic ports — every BSPP port on a pump, valve, cylinder, manifold or hose tail across mobile hydraulics, industrial hydraulics and aerospace. Pneumatic fittings — air compressor outlets, BSPP air-line manifolds, regulator inlets, FRL (filter-regulator-lubricator) groups. Fuel system unions — diesel return lines, fuel filter housings, injector pump fittings (Viton needed for modern diesel and ethanol-blend petrol). Lubrication and grease fittings — banjo bolt feeds on automatic lubricators, central lubrication system manifolds. Gauge ports and instrumentation — pressure gauge fittings, transducer bosses, sample ports — small sizes (1/8", 1/4" BSPP). Sump plugs and drain plugs — engine oil pans, gearbox housings, hydraulic reservoirs. Many OEM sump plugs ship with a bonded seal or aluminium-bonded equivalent. Brake banjo fittings — increasingly used on modern motorcycle and automotive brake banjos as a more forgiving alternative to copper crush washers (must be EPDM rubber for DOT 3/4/5.1 brake fluid — read the next section). Compressed gas and refrigerant fittings — refrigeration service ports, gas regulator outlets (FKM rubber, never NBR). Dowty Washer vs Copper Crush Washer vs O-Ring vs Loctite Pipe Sealant Four different ways to seal a threaded fitting or bolted port. Picking the wrong one is a guaranteed leak. Quick comparison: Sealing Method Works On Reusable? Strengths Weaknesses Bonded seal (Dowty) Parallel thread, flat-face port Single-use recommended; sometimes reusable if undamaged Forgiving torque range, no thread prep, fast install, no cure time Wrong rubber for fluid = fail; doesn't suit tapered thread Copper crush washer Parallel thread, flat-face port; banjo bolts Single-use only — copper work-hardens on first crush Brake fluid compatible, very high temp range, classic banjo bolt seal Hardens after one tighten — reuse leaks; requires higher torque to crush O-ring face seal O-ring boss ports (SAE J1926), ORFS fittings, machined groove Replace if damaged, often reused Highest reliability when port has a proper groove; standard on premium hydraulics Needs machined groove or boss — can't be retrofitted to a flat-face BSPP port Thread sealant (Loctite 567/577, PTFE tape) Tapered thread (BSPT, NPT) Reapply on every disassembly Only correct method for tapered thread; cheap; fills imperfect threads Doesn't seal parallel thread; PTFE tape on BSPP ruins bonded seal seating Common mismatches and what goes wrong: Bonded seal on tapered thread → no flat face to compress against, rubber distorts and weeps within hours. Use thread sealant. PTFE tape on BSPP port → tape sits under the bonded seal and stops it seating against the spotface. Apparent tightness, slow weep. Remove tape, install bonded seal alone. Copper crush washer reused → work-hardened from first install, won't deform enough on second torque. Use new every time, or switch to bonded seal. NBR bonded seal on brake fitting with DOT 4 fluid → rubber swells and softens, seal fails within months. Use EPDM bonded seal or copper crush. O-ring boss fitting (SAE J1926) tightened without the O-ring → no seal at all; flat washer underneath does nothing without the elastomer. Always check for and install the correct O-ring. Installation — Which Way Does the Rubber Face? The bonded seal is asymmetric — the rubber sits proud on one face of the metal washer and is flush with the other. The convention across hydraulic component manufacturer documentation (Hutchinson, Trelleborg, James Walker, Parker) and verified across mechanic forums is: The rubber face contacts the mating face (the flat machined surface being sealed). The metal back faces the bolt head or fitting shoulder. This is because: The bolt head or fitting flange is hard, machined steel — there's nothing to seal against that. The rubber serves no purpose between bolt head and metal washer. The mating face (the port spotface or component face) is where the leak path is. The rubber needs to be against that face to compress and seal it. The metal back distributes the bolt clamping load evenly across the rubber — it acts as a follower plate. In practice it's hard to install one upside down because the rubber-proud face is visually obvious. But on small sizes (1/8" BSPP) it's worth a deliberate check before tightening — particularly if you're working blind in a confined space. Other installation rules: Mating face condition — the seal will only seal as well as the surface it compresses against. Wipe the spotface clean of old sealant residue, oil and grit before assembly. A nick or scratch radial across the spotface will give a permanent weep. No thread tape, no Loctite, no extra goop — a bonded seal on a parallel thread needs nothing else. Adding PTFE tape under it actively prevents it sealing. Adding Loctite 577 won't hurt the seal but is pointless on a parallel thread. Torque — most BSPP fittings have a recommended torque in the component manual. As a rough guide for hydraulic adapters: 1/4" ~ 25 Nm, 3/8" ~ 50 Nm, 1/2" ~ 90 Nm, 3/4" ~ 175 Nm. The bonded seal is forgiving — within ±25% of these figures it will seal. Severe over-torque can split the rubber. One direction of rotation — tighten in one continuous motion to spec. Don't tighten, back off and re-tighten — that disturbs the rubber and can leave a witness line on the mating face that becomes the leak path on reassembly. Single-Use Rule — Why Bonded Seals Are (Mostly) Single-Service Manufacturer specification sheets often allow limited reuse of bonded seals if undamaged. Mechanic forum consensus (Mini Forum, MG Experience, Practical Machinist, Yesterday's Tractors) is firmly against it for any pressurised system: The rubber takes a compression set on first install. When you back the fitting off, the rubber doesn't fully spring back. The next install starts with less rubber height available to seal. If the rubber has been heat-cycled (engine bay, hot hydraulics) the compound has aged in place. Refitting introduces a stiffer, less compliant seal to a fresh mating face. Any nick or scratch on the rubber from disassembly tools — pick, screwdriver, fingernail — becomes a leak path. The cost of a bonded seal is typically $0.30–$2.00. The cost of chasing an intermittent hydraulic leak through a multi-fitting circuit is hours of labour and a customer return. Rule of thumb: if the fitting comes apart, the bonded seal gets replaced. The only exception is dry, low-pressure pneumatic work where a quick disassembly-reassembly within minutes (e.g. setting fitting orientation on a new install) is reasonable. Note that this is more conservative than the supplier line. Suppliers state bonded seals can be reused. Real-world maintenance practice on production hydraulics is to use new every time — labour cost of investigating a recurring weep dwarfs the parts cost ten times over. AIMS Industrial Bonded Seal / Dowty Washer Range AIMS Industrial stocks bonded seal washers across the full BSP parallel and metric range used in Australian hydraulics, pneumatics and fluid handling. NBR is our standard stock compound — Viton (FKM) available on order for fuel system, hot oil and refrigerant applications. Browse the range: Sealing & Cushioning Washers — full bonded seal range plus crush washers and cushioning washers All Washers — flat, spring, structural, bonded seal and specialty Hydraulic Fittings — BSPP adapters, hose tails, banjo unions and the bonded seals to suit Hydraulic Components — pumps, valves, cylinders, hose Air Tools & Pneumatics — pneumatic fittings, regulators and the bonded seals they need Loctite Range — for the tapered-thread fittings that need thread sealant instead Thread Sealants — Loctite 567, 577 and PTFE tape for BSPT/NPT fittings Not sure which seal you need or what's leaking? Call our team on (02) 9773 0122 — bring or send a photo of the fitting and the male thread, and we'll match the right seal for the fluid, temperature and pressure. We stock for the trade so we know what's actually used on Australian shop floors, not just what's in the catalogue. FAQ — Dowty Washers and Bonded Seals What's the difference between a Dowty washer and a bonded seal? There is none. Dowty washer is a brand name (Dowty Seals Ltd, UK) that became the generic Australian term for bonded seal washers. The patent expired decades ago and the term now describes the design, not the brand. Most washers stocked as "Dowty washers" in Australian fastener catalogues are made by Hutchinson, Trelleborg, James Walker or generic Asian manufacturers. Can I use a bonded seal on an NPT or BSPT fitting? No. Bonded seals only work on parallel-thread fittings with a flat spotface to compress against. NPT and BSPT seal by metal-to-metal wedging of tapered threads — there's no flat face for the rubber to seal against. Use Loctite 567, Loctite 577 or PTFE thread tape on tapered fittings. This is the most common cause of leaks among DIY hydraulic installers. Which way does the rubber face — towards the bolt or towards the seal face? The rubber face contacts the flat machined surface being sealed (the port spotface or component face). The metal back of the washer sits against the bolt head, fitting shoulder or flange. This is consistent across all major manufacturer documentation. On smaller sizes it can be hard to tell visually — feel for the slightly proud rubber side and put that towards the sealing face. Can I reuse a Dowty washer? Manufacturers say yes if undamaged. Production hydraulic mechanics say no — always use new on any pressurised fitting. The cost of a bonded seal is $0.30–$2.00; the cost of chasing a recurring weep is hours of labour. The rubber takes a compression set on first install and doesn't fully spring back, so the second install starts with less seal height. Reuse is reasonable on dry low-pressure pneumatic work for trial-fitting purposes. What rubber compound do I need for hydraulic oil? NBR (Nitrile, Buna-N) is the standard compound for mineral hydraulic oil — covers HLP, HM, HV grades and standard ISO VG 32/46/68. For hot hydraulic systems running >100°C return-line temperature, or for fire-resistant fluids (HFC water-glycol, HFD phosphate ester), step up to FKM (Viton). For water-glycol HFC use EPDM. Never use NBR on phosphate ester (HFD) — it swells and fails. Can I use a Dowty washer on a brake banjo bolt? Only if the rubber is EPDM. Standard NBR bonded seals will fail on DOT 3, DOT 4 or DOT 5.1 brake fluid — the glycol-based fluid attacks the nitrile rubber. EPDM bonded seals are compatible. Note that DOT 5 (silicone-based) brake fluid is the exception — NBR is fine with DOT 5. Most automotive brake banjos still use copper crush washers as the OEM seal because copper is universally fluid-compatible. If you're switching to a bonded seal on a brake fitting, confirm the rubber compound first. Why does my BSP fitting still leak with a new Dowty washer? Five likely causes in rough order of frequency: (1) it's actually a BSPT fitting not BSPP — check by hand-threading the male and seeing if it stops at a flat shoulder or tightens up partway in; (2) PTFE tape was wrapped on the thread under the bonded seal — remove the tape, the seal needs direct contact with the spotface; (3) the spotface is scratched or has old sealant residue — clean it and check for a radial nick; (4) the wrong size washer is being used and isn't compressing properly; (5) the bonded seal is upside down — rubber must face the sealing surface. Do I need to use thread sealant with a Dowty washer? No. On a BSPP parallel-thread fitting with a bonded seal, no thread tape, no Loctite and no liquid sealant should be applied. The bonded seal does the sealing on its own at the spotface. Adding PTFE tape actively prevents the bonded seal seating and is the second most common cause of BSPP leaks after thread-type confusion. What torque should I use on a bonded seal fitting? Follow the component manufacturer's torque spec where available. As a working guide for hydraulic BSPP adapters: 1/8" ~ 15 Nm, 1/4" ~ 25 Nm, 3/8" ~ 50 Nm, 1/2" ~ 90 Nm, 3/4" ~ 175 Nm, 1" ~ 300 Nm. The bonded seal is forgiving — within ±25% of these values it will seal. Severe over-torque can split the rubber and create a leak. Are bonded seals OK for fuel systems? Yes for diesel and traditional petrol with NBR (Nitrile). For modern Australian ethanol-blend petrol (E10, E85), upgrade to FKM (Viton) — NBR hardens and cracks within 12 months on ethanol-blend fuel. For LPG and gas systems, check the rubber compatibility with the specific gas — Viton is usually safe, NBR is hit-and-miss. What's the difference between a Dowty washer and an O-ring face seal fitting (ORFS)? A Dowty washer is an add-on component — slip it under any flat-face BSPP fitting. An O-ring face seal fitting (ORFS, SAE J1453) is a fitting type with a machined O-ring groove built into the face. Both seal by elastomer compression against a flat face. ORFS is the higher-reliability standard on premium hydraulics because the O-ring is captive in a groove and can't fall out. Dowty washers are more flexible because they fit any standard BSPP port — no special machining required. Can I make a bonded seal at home from a flat washer and an O-ring? For very low-pressure pneumatic or static water applications, yes — combining a flat washer with an O-ring underneath approximates the bonded seal function. For any hydraulic or pressurised fluid application, no. The bonded rubber-to-metal vulcanisation is what stops the rubber extruding sideways under pressure. A loose O-ring on a flat washer will squeeze out radially and the joint will weep at any meaningful pressure. Why are stainless steel bonded seals more expensive? Stainless steel (304 or 316) bonded seals run 3–6× the price of zinc-plated carbon steel equivalents because of raw material cost and because bonding rubber reliably to passive stainless surfaces requires more aggressive surface preparation. They're worth it in marine, food contact, pharmaceutical and aggressive chemical service where carbon steel would rust at the bond line and break the seal. Where do I find the right size bonded seal for my fitting? Match the bore to the male thread size and check the outer diameter fits inside any counterbore on the female component. AIMS keeps the standard BSPP and metric range in stock — call us on (02) 9773 0122 with the thread size of your fitting and we'll match it. If you're unsure of the thread, send a photo or bring the fitting in to our Milperra warehouse. Pair this with our Thread Standards Guide for the parallel-vs-tapered distinction and AS 1722 standards. People Also Ask — Dowty Washers and Bonded Seals Q: What is a Dowty washer and what is it used for? A Dowty washer (bonded seal) is a metal washer with a rubber sealing ring bonded to one face. It creates a leak-free face seal on parallel-threaded ports in hydraulic, pneumatic, fuel, and lubrication systems by compressing the rubber between the fitting face and the port seat. Q: Why do bonded seals only work on parallel thread fittings? Bonded seals rely on face-sealing — the rubber compresses against a flat seating surface as the fitting is tightened. Tapered threads (BSP taper, NPT) seal by thread engagement, not on a flat face. A bonded seal cannot form a proper seal on a tapered thread port. Q: What rubber materials are available and when should each be used? NBR (nitrile) is the standard choice for hydraulic oil, diesel, and lubricants. Viton/FKM suits aggressive chemicals and high-temperature environments. EPDM is used for water and steam applications. Matching the elastomer to the fluid is critical — the wrong material will swell, harden, or degrade in service. Q: Are bonded seals single-use items? In most applications, yes. A bonded seal that has been compressed and released has already deformed to the port face; re-using it risks an incomplete seal and potential leakage. For safety-critical hydraulic and fuel connections, replace the bonded seal every time the fitting is disturbed. Q: Which way does the rubber ring face when installing a bonded seal? The rubber ring faces toward the port seating face — downward into the port. The metal washer sits against the underside of the fitting head. The rubber must compress against the flat port face as the fitting is tightened; if installed inverted, no seal is formed. Looking for roll groove fittings? Our roll groove fittings range covers the common sizes and brands. Need oil seals o rings? Browse the AIMS range at oil seals o rings.
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