Product Guides
Socket Set Guide: Drive Sizes, Deep vs Shallow & Metric vs Imperial
A socket set is one of the most-used tools in any workshop — and one of the most misunderstood when it comes to buying and using one correctly. Choose the wrong drive size and you're fighting a tool that's either too bulky to get in or too light to break the bolt loose. Grab a shallow socket on a stud bolt and it won't seat. Put a chrome socket on an impact gun and you risk it shattering under load. This guide covers the decisions that actually matter: drive sizes and what they're rated for, when to use deep versus shallow sockets, how metric and imperial relate to each other in the Australian context, and the difference between standard and impact sockets. By the end you'll know exactly what to buy first and how to build your set from there. Socket Sizes & Drives — Quick Reference The two decisions that matter most when buying a socket set: drive size (the square fitting on the back that connects to the ratchet) and socket depth (standard/shallow vs deep). Drive Size Common Use Bolt Size Range 1/4" Light DIY, electronics, small fasteners M3 – M8 3/8" General workshop, automotive maintenance M6 – M14 1/2" Automotive, heavy maintenance, wheel nuts M10 – M22 3/4" Truck, mining, structural and industrial M20 – M36 Standard (shallow) sockets are for bolt heads and nuts sitting on short studs. Deep sockets are needed for long studs, spark plugs and recessed fittings where the bolt protrudes through the nut. A complete workshop set has both depths. Socket Profile Types: 6-Point vs 12-Point Sockets are available in 6-point (hex) and 12-point (bi-hex) profiles. The choice affects both the grip on the fastener and the ease of positioning the socket. A 6-point socket contacts the fastener at the flat faces of the hex, not the corners. This distributes force across a wider area and significantly reduces the risk of rounding a fastener — particularly on older, corroded, or already-chewed fasteners. For maintenance work where fasteners may not be in perfect condition, 6-point is the correct choice. A 12-point socket has twice as many engagement positions, which means less ratchet arc is needed to reposition — useful in confined spaces where the ratchet cannot swing far. The trade-off is that 12-point sockets contact the fastener at the corners rather than the flats, concentrating force on smaller contact areas and increasing the risk of rounding. For most maintenance and trade applications, 6-point sockets are the better choice. 12-point sockets have their place in confined-space work where positioning flexibility is critical, but they should be used on fasteners in good condition. What Is a Socket Set? A socket set is a collection of sockets paired with the ratchets, extensions, and adapters needed to drive them. The socket itself is a hollow, cylindrical tool that fits over a fastener — a bolt head or nut — and transfers torque from the ratchet to the fastener. The key parts of a socket set are: Sockets — the hollow cylinders that engage the fastener. Available in metric and imperial sizes, in shallow and deep lengths, and in 6-point and 12-point profiles. Ratchet — the handle with a one-way mechanism that lets you turn without repositioning. The square drive on the end mates with the socket. Extension bars — add reach between the ratchet and socket when you can't get the ratchet directly over the fastener. Available in short (50–75mm), medium (150mm), and long (250–300mm) lengths. Universal joint (U-joint) — allows the socket to work at an angle, useful for off-axis fasteners. Breaker bar — a long, fixed (non-ratcheting) bar for high-torque initial loosening. Adapters — allow you to use a socket of one drive size with a ratchet of another (e.g., 1/2" socket on a 3/8" ratchet). The drive size — the square male fitting on the ratchet that locks into the socket's square female recess — ties the system together. Every socket and ratchet in a set shares a common drive size. Socket Drive Sizes Explained: 1/4", 3/8", 1/2" and 3/4" Drive size refers to the side length of the square male drive on the ratchet or breaker bar. The four standard sizes are 1/4", 3/8", 1/2" and 3/4". These dimensions are imperial measurements regardless of whether the sockets themselves are metric — drive sizes have always been expressed in inches and are universal across metric and imperial socket sets worldwide. Drive size determines the torque capacity of the system, the size of the ratchet and sockets, and the access geometry. Bigger drive = more torque capacity, larger tool head, harder to get into tight spaces. 1/4" Drive 1/4" drive is the smallest common drive size, intended for low-torque work in confined spaces. The compact ratchet head fits into areas a 3/8" cannot reach. Common applications include interior trim and panel fasteners, electrical components, small engine parts, and precision assembly work. Typical torque capacity is around 35–60 Nm. Going beyond this risks snapping the drive or rounding the fastener. Socket sizes in 1/4" drive typically range from 4mm to 15mm metric (or 5/32" to 9/16" imperial). 3/8" Drive 3/8" drive is the most common all-around drive size for a reason: it covers the majority of fasteners encountered in automotive, light industrial, and general maintenance work, with a ratchet head small enough to fit most access points. It is the starting point for any socket set collection. Typical torque capacity is 80–200 Nm — sufficient for most standard fasteners. Socket range in 3/8" drive runs from around 6mm to 22mm metric (or 1/4" to 7/8" imperial). A practical rule used by tradespeople: stay on 3/8" drive for sockets up to 19mm. Beyond that, move to 1/2". 1/2" Drive 1/2" drive is the standard for automotive work, suspension and brake jobs, and heavier industrial maintenance. The larger ratchet head is bulkier but the torque capacity — typically 200–600 Nm — handles wheel nuts, hub bolts, and structural fasteners that would snap a 3/8" drive. 1/2" drive is also the standard pairing for impact wrenches in workshop settings. Socket sizes run from around 10mm to 32mm metric, or 3/8" to 1-1/4" imperial. Impact-rated 1/2" socket sets are common in automotive workshops. 3/4" Drive 3/4" drive is used for heavy plant equipment, trucks, mining machinery, and structural bolting where torque requirements are very high. This is specialist territory — ratchets are large, sockets are heavy, and the system is designed for bolts that would be damaged or impossible to remove with a 1/2" drive setup. Most general workshops won't need a 3/4" drive set. Which Drive Size Should I Start With? Start with 3/8" drive. It handles the broadest range of fasteners, fits most access points, and covers the gap between light bench work and serious automotive jobs. If you only ever own one socket set, make it a 3/8" metric set from 8mm to 24mm. Add 1/4" drive when you regularly work on small fasteners, electronics, interior trim, or anywhere the 3/8" ratchet head is physically too large to position correctly. Many tradespeople keep a small 1/4" set in their kit for these situations without replacing their 3/8" set. Add 1/2" drive once automotive work — wheels, suspension, brakes, engine mounts — becomes a regular part of your workload. The torque capacity difference between 3/8" and 1/2" is significant, and using a 3/8" drive on high-torque fasteners risks breaking the ratchet mechanism or the drive square on the socket. Many experienced tradespeople end up with all three. The 3/8" gets the most use by a significant margin. Deep vs Shallow (Standard) Sockets: When to Use Each Socket depth refers to how far the socket's internal hex or 12-point profile extends from the drive end to the open end. A shallow (standard) socket typically has 20–30mm of internal depth. A deep socket runs 50–70mm or more. When You Need a Deep Socket Use a deep socket when the fastener itself protrudes significantly through the nut — as with threaded rod and stud bolts — or when the bolt shank is long enough that a shallow socket cannot seat fully on the nut. Common examples: Wheel nuts on stud bolt wheels — the stud extends beyond the nut, requiring depth clearance Spark plugs — the plug sits recessed in the head, too deep for a standard socket (spark plug sockets are a specific type of deep socket with a rubber insert) Suspension fasteners — bolts with significant thread protrusion Electrical terminals and battery terminals — often with long bolt lengths The 10mm deep socket deserves a specific mention. It is the most frequently needed deep socket in automotive and general workshop work — under bonnets across almost every modern vehicle, you will find 10mm fasteners with enough thread protrusion to require depth. It is also the socket that gets misplaced most often in every workshop in Australia. Deep sockets also have more mass than shallow sockets of the same size. When paired with an impact wrench, this extra mass helps break loose stubborn high-torque fasteners. Some tradespeople default to deep sockets even when depth isn't strictly required for this reason. When Shallow Sockets Are Better Use shallow (standard) sockets when access is restricted and the compact length of the socket gives better working geometry. In a confined engine bay or below the dash, a deep socket on an extension can create leverage problems and introduce unnecessary flex into the drive path. A shallow socket directly on a short extension is steadier. Shallow sockets are also better when the ratchet head must be positioned at a tight angle — the shorter drive path reduces the leverage required and the chance of the socket walking off the fastener. The practical approach: if your set includes both depths, reach for the shallow socket first. If it won't seat, switch to deep. If you're building a kit and budget is limited, prioritise a full shallow set first, then add deep where you know you need it — typically 10mm, 12mm, 13mm, 17mm, and 19mm deep to start. Metric vs Imperial Sockets In Australia, the vast majority of modern equipment — vehicles, machinery, and industrial fasteners — uses metric thread standards. An Australian workshop set in metric will cover almost all day-to-day work. Imperial (SAE — Society of Automotive Engineers) sockets remain relevant in a few specific situations: American-manufactured equipment — US trucks, machinery, and older imported vehicles often use imperial fasteners Classic and vintage vehicles — pre-metric Australian and British vehicles (pre-1970s) used Whitworth or BSF fasteners, though these require dedicated Whitworth socket sets rather than standard imperial Some hydraulic fittings — JIC and NPT hydraulic fittings use imperial thread specifications One point worth clarifying: drive sizes (1/4", 3/8", 1/2") are always expressed in imperial inches regardless of whether you are using metric or imperial sockets. A 3/8" drive ratchet drives both metric and imperial sockets — the drive size and the socket measurement system are unrelated. There are also near-equivalent sizes between metric and imperial that tradespeople sometimes use as a workaround when the exact size is unavailable. For reference: 11mm ≈ 7/16", 13mm ≈ 1/2", 14mm ≈ 9/16", 17mm ≈ 11/16", 19mm ≈ 3/4", 22mm ≈ 7/8", 24mm ≈ 15/16". These are close enough to work in a pinch on soft metals but can round hardened fasteners — always use the correct size where possible. For a complete metric and imperial socket size reference, including common size ranges by drive size, see the AIMS Socket Size Chart: Metric & Imperial with Drive Sizes. Standard vs Impact Sockets: The Critical Difference Standard (chrome) sockets and impact sockets look similar but are built for different purposes. Using the wrong type on an impact tool is a safety issue, not just a tool wear issue. Standard (Chrome Vanadium) Sockets Standard sockets are made from chrome vanadium steel and given a chrome plating finish. They are designed for hand tools — ratchets, torque wrenches, and breaker bars — where the force applied is smooth and controlled. Chrome vanadium is hard and holds its shape well under steady torque. The thinner wall of chrome sockets is a deliberate design choice. It reduces the outside diameter of the socket, improving clearance in tight spaces. Do not use chrome (standard) sockets on impact tools. Impact wrenches apply sudden, high-energy pulses rather than steady torque. Chrome vanadium cannot absorb this shock loading the way impact-rated steel can — it can crack or shatter under impact, creating projectile fragments. This is not a remote possibility; it is a documented failure mode. Impact Sockets Impact sockets are made from chrome molybdenum (chrome-moly) steel, which is tougher and more ductile than chrome vanadium. The material deforms under overload rather than fracturing — a much safer failure mode. Impact sockets have thicker walls to distribute the shock loading of impact tool use. The thicker wall means impact sockets have a larger outside diameter for the same fastener size. In tight spaces, this can be a problem — a chrome socket that fits may be replaced by an impact socket that won't clear the surrounding structure. This is one reason tradespeople carry both types. Impact sockets are typically finished in a matte black phosphate rather than chrome, which makes them easy to distinguish from standard sockets at a glance. As a general rule: use chrome sockets for hand tool work and torque wrench work. Use impact sockets with impact wrenches and air tools. Other Socket Types Worth Knowing Torx (star) sockets are increasingly common in automotive applications, particularly European and modern Asian vehicles. Torx drive provides excellent torque transfer with minimal cam-out. Common sizes are T40, T45, T47, T50, T55, and T60 for automotive work. Spline sockets are used in specialised high-torque applications. The multiple lobes of the spline engagement distribute load across a larger contact area than a standard hex profile, making them suitable for fasteners that are heavily stressed in service. Spark plug sockets are a type of deep socket with a rubber or foam insert that grips the ceramic insulator of the spark plug, allowing it to be withdrawn from the plug recess without dropping. They are available in the two common spark plug hex sizes — 16mm and 21mm. Hex bit sockets (Allen key sockets) accept a hex bit and convert it to a socket drive. Useful for internal hex (Allen) fasteners that need more torque than a T-handle or L-key can provide. Pass-through sockets are open at both ends, allowing them to fit over threaded rod or long bolts that extend beyond the nut. Useful in construction and structural applications. Building Your Socket Set: A Practical Starting Point Rather than buying the cheapest 200-piece set you can find, build deliberately. Most of those pieces never get used, and the quality is often poor across the board. A solid starting kit for a trade or maintenance workshop: 3/8" drive metric socket set, 6-point, shallow — 8mm to 22mm at a minimum. This covers the majority of everyday fasteners. 3/8" drive ratchet — 72-tooth or higher for a finer engagement arc. A breaker bar is a useful addition for initial loosening. Extension set for 3/8" — short (75mm), medium (150mm), and long (250mm) covers most reach requirements. 3/8" drive metric deep socket set — 10mm, 12mm, 13mm, 17mm, and 19mm as a minimum. These are the depths you will actually need regularly. Add from here based on the work you do: 1/4" drive set for fine and confined work 1/2" drive set for automotive and heavy maintenance Impact socket set (black, chrome-moly) for impact tool use Torx and hex bit socket sets as your equipment requires Quality matters more for sockets that are used heavily. For a workshop that uses them daily, invest in a reputable brand. For occasional use, a mid-range set is adequate — but avoid the very cheapest options, where the heat treatment and tolerances are often poor enough that sockets round off at the drive square under normal load. Frequently Asked Questions What drive size should I buy first? Start with 3/8" drive. It handles the widest range of fasteners for general automotive, maintenance, and trade work. Most experienced tradespeople reach for their 3/8" set first and only switch to 1/4" or 1/2" when the job specifically requires it. Can I use a 3/8" drive socket on a 1/2" drive ratchet? Not directly — the square drive sizes must match. You can use an adapter to convert between sizes (e.g., a 3/8" to 1/2" adapter), but be aware that using a smaller socket on a larger drive setup means the socket becomes the weak link in the chain. Use the correctly-rated drive for the torque involved. What is the difference between a 6-point and 12-point socket? A 6-point socket grips the flat faces of the fastener hex and is much less likely to round a fastener. A 12-point socket has twice as many positioning points, which is useful in restricted spaces where you can only swing the ratchet a short arc, but it contacts the corners of the fastener and can round them under high torque. For most maintenance work, 6-point is the better choice. Can I use standard chrome sockets on an impact wrench? No. Standard chrome vanadium sockets are not designed to absorb the shock loading of impact tools. Under impact use, they can crack or shatter, creating fragments. Always use impact-rated (chrome-moly, typically black-finish) sockets with impact wrenches and air tools. Do I need both metric and imperial socket sets in Australia? For most Australian tradespeople, a metric set covers the vast majority of work. Imperial sockets are specifically needed when working on American-manufactured equipment, some older vehicles, or hydraulic systems with JIC/NPT fittings. If you occasionally encounter this work, a supplementary imperial set is worth having. If not, a metric-only set is the practical choice. What is the difference between deep and shallow sockets? Deep sockets have a longer internal cavity — typically 50–70mm versus 20–30mm for shallow sockets. Deep sockets are needed when the fastener has significant thread protrusion above the nut (as with stud bolts and wheel nuts), or when the socket must reach a fastener recessed into a housing. Shallow sockets have a smaller overall profile and are easier to use in confined spaces. Which is better for impact tools — deep or shallow sockets? For impact use, both can be used in impact-rated (chrome-moly) form. Deep impact sockets are often preferred because the extra mass of the socket helps drive home stubborn fasteners. However, shallow impact sockets are better in tight spaces where the added length of a deep socket creates clearance problems. Use whichever fits the application — the material rating matters more than the depth. What does torque rating mean for a socket set? Torque rating is not typically published for individual sockets, but drive size is a reliable proxy. 1/4" drive handles up to approximately 35–60 Nm safely. 3/8" drive handles up to approximately 80–200 Nm. 1/2" drive handles up to approximately 200–600 Nm. Going significantly beyond these ranges risks damaging the drive square on the socket or ratchet mechanism. Always use a torque wrench for precision fastening — a ratchet alone cannot tell you how much torque you've applied. Are cheap socket sets worth buying? It depends on the intended use. For occasional light work, a mid-range set from a reputable supplier is adequate. Avoid the very cheapest options — budget socket sets often have poor heat treatment, meaning the drive squares deform under load and the sockets round off quickly. For daily trade use, the cost difference between a budget set and a quality set is recovered quickly in fewer replacements and less time fighting slipping tools. Buy the best you can justify for the frequency of use. What size socket is used most often? 10mm and 13mm are the most commonly reached-for sizes in automotive and general workshop work in Australia. On modern vehicles specifically, 10mm covers a significant proportion of under-bonnet fasteners. 19mm is the most common wheel nut size on passenger vehicles and light commercials. Can I mix socket brands on the same ratchet? Yes, within the same drive size. The square drive is a standardised dimension — a 3/8" socket from any manufacturer will fit a 3/8" ratchet from any other manufacturer. There may be minor variation in fit tightness (a worn ratchet drive or a loose-toleranced socket can cause the socket to wobble), but cross-brand mixing is standard practice in workshops. What is a universal joint (U-joint) socket adapter used for? A universal joint allows the ratchet to work at an angle to the socket, which is necessary when the fastener is offset from the available access point. For example, when a bolt is visible but the ratchet cannot be positioned directly in line with it. U-joints reduce the torque that can be applied safely — the more extreme the angle, the greater the side-loading on the drive. Use an extension to offset the ratchet rather than extreme U-joint angles where possible. Cross-reference our Spanner Size Chart when you need to size a spanner to a metric or imperial fastener head. People Also Ask — Socket Sets Q: What drive size socket set should I buy for general automotive and mechanical work? A 3/8" drive socket set is the most versatile choice for general automotive and mechanical work — compact enough for access in tight spaces yet strong enough for most standard fastener sizes. Many mechanics own a 3/8" set as their primary tool and supplement it with a 1/4" drive set for smaller fasteners and a 1/2" drive set for larger bolts and wheel nuts. Impact work requires a dedicated 1/2" drive impact socket set rather than using standard chrome-vanadium sockets, which are not rated for impact loading. Starting with a quality 3/8" metric set covers the majority of workshop tasks. Q: What is the difference between a standard socket and a deep socket? A standard socket has a shorter profile designed to fit over a fastener head with minimal extension below the nut face. A deep socket has a longer internal depth, allowing it to fit over a bolt that protrudes significantly through a nut, or to reach nuts recessed down into a cavity. Deep sockets are commonly used for spark plugs, wheel studs, and nuts on threaded rod. The trade-off is that deep sockets have slightly less lateral stability than standard sockets, so they are best used with an extension bar rather than directly on a ratchet when torque accuracy is important. Q: Can I use standard chrome-vanadium sockets with an impact wrench? No — standard chrome-vanadium sockets should not be used with an impact wrench. Standard sockets are designed to resist the steady torque of hand ratchets and torque wrenches, but the sudden shock pulses of an impact wrench can crack or shatter them, creating a serious safety hazard. Impact sockets are made from more ductile chrome-molybdenum steel with thicker walls specifically to absorb impact shock without fracturing. They are usually finished in black oxide rather than chrome plating. Only use sockets rated for impact use with impact tools — the packaging or body of the socket will clearly indicate impact rating. Q: What is a bi-hex (12-point) socket and when should you use it? A bi-hex socket has 12 internal contact points rather than the 6 of a standard hex socket, allowing it to be positioned on a fastener at twice as many rotational positions. This is useful in confined spaces where the ratchet cannot swing through a full 60° arc. The trade-off is that 12-point sockets apply force at the corners of fastener flats, making them more likely to round off worn or corroded fasteners. For regular use on good fasteners, 12-point sockets work well; for removing stubborn or damaged fasteners, a 6-point socket provides better grip and reduces the risk of rounding the flats. Q: How do I know which socket size fits a metric bolt? Metric sockets are sized by the measurement across the fastener flats (AF dimension in millimetres). The socket size corresponds to the AF measurement of the nut or bolt head — for example, an M8 bolt typically has a 13mm AF head, requiring a 13mm socket. The AF size is stamped on the side of each socket. For common metric fasteners, standard size pairings are: M6 = 10mm, M8 = 13mm, M10 = 17mm, M12 = 19mm, M16 = 24mm. Hex socket head cap screws use different hex key sizes rather than AF sockets. When in doubt, trying the next size up or down finds the correct fit quickly. Looking for metric spiral point taps? Our metric spiral point taps range covers the common sizes and brands. Looking for strong hand? Our strong hand range covers the common sizes and brands.
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Types of Spanners Guide: Types, Sizes & Selection
Spanner vs Wrench — What's the Difference? In Australian and UK English, "spanner" is the standard trade term for a fixed-size hand tool used to turn hex nuts and bolts — ring spanners, open-end spanners, combination spanners. "Wrench" is the US term for the same tools. Both words describe the same family of fasteners-turning tools; only the regional usage differs. Are spanners and wrenches interchangeable terms? Mostly yes — but with one consistent exception. Adjustable-jaw tools (Crescent-style adjustables, pipe wrenches, monkey wrenches) are called "wrenches" worldwide, including in Australia. Fixed-size hex-fitting tools are called "spanners" in Australia and the UK, and "wrenches" in the US. So in an Australian workshop you'll hear "pass me the 19 mm spanner" and "pass me the pipe wrench" in the same conversation. Spanners are the backbone of any trade toolkit — and choosing the wrong type is one of the most reliable ways to round a nut, strip a fitting, or find yourself stuck halfway through a job. This guide covers every type of spanner used in Australian trades and workshops: what each one does, when to use it, and where it fails. Whether you are a maintenance fitter, tradie, mechanic, or setting up a home workshop, this is the complete reference. Spanner or Wrench? The Australian Terminology In Australia, the correct trade term is spanner. In the United States, the same tool is called a wrench. Both terms are understood in Australia, but spanner is the standard in trade settings. Some specific tools retain "wrench" in their name regardless — torque wrench, pipe wrench, and impact wrench are all normal Australian terminology. One important AU-specific term: shifter refers specifically to an adjustable spanner, not to all spanners. If someone on site asks for "the shifter," they mean the adjustable. "A spanner" means the correctly-sized fixed spanner for the job. ℹ️ Note: This guide uses Australian convention throughout — spanner for the tool category, with the US term noted where relevant. The term wrench is retained only in specific tool names (torque wrench, pipe wrench, impact wrench) where that is standard Australian trade usage. The Main Types of Spanners Explained There are more than a dozen distinct spanner types, each designed for specific access conditions, fastener types, and torque requirements. Understanding the limitations of each type is as important as knowing its intended use. 1. Open-End Spanner The open-end spanner has two fixed U-shaped jaws at opposite ends, set at 15° to the handle axis. Most are double-ended with two different sizes (e.g. 10/11mm, 12/13mm, 16/17mm). The 15° offset allows the tool to be flipped end-for-end after each partial turn — effectively doubling the usable arc in confined spaces. Best for: Quick access where a ring or socket cannot fit above the fastener; holding a nut while tightening from the opposite side; pipe fittings where a ring cannot thread over the tube end. Limitation: The open jaw contacts only two faces of the fastener. Under high torque, this concentrates stress on two points and causes slipping and rounding. Open-end spanners are run-down and access tools — not break-out tools. ⚠️ Warning: Never use an open-end spanner for heavy break-out torque on corroded or overtightened fasteners. Two-point contact will round the corners before the fastener moves. Use a ring spanner or socket for break-out — switch to open-end only once the fastener is already moving. 2. Ring Spanner (Box End Spanner) A ring spanner has a fully enclosed circular head engaging all six faces of a hex fastener (twelve engagement points in a bi-hexagonal design). This full engagement makes it the strongest fixed spanner type and the correct choice for any high-torque or corroded fastener situation. 6-point vs 12-point (bi-hexagonal): Most Australian ring spanners are bi-hex (12-point). A 12-point ring repositions every 15° of swing; a 6-point requires 30°. In tight spaces with a limited swing arc, 12-point ring spanners complete a full rotation in half the repositioning lifts. Six-point rings distribute force more evenly per flat and are preferred for extreme torque or already-damaged fasteners. Best for: High-torque applications, corroded or seized fasteners, repetitive tightening cycles where fastener rounding must be avoided. 📌 Key Fact: A 12-point bi-hexagonal ring spanner can be repositioned every 15° — half the arc required by a 6-point ring. In a confined space where the handle can only travel 20° before hitting an obstruction, this difference can determine whether the job is achievable at all. 3. Combination Spanner The combination spanner is the most common spanner in Australian trade toolkits. It has an open-end jaw on one end and a ring on the other — both the same size. A 17mm combination spanner gives you a 17mm open end and a 17mm ring on one tool. The open end runs the fastener down quickly; the ring end provides final high-torque drive or initial break-out grip. One tool, two functions, same size. A metric set from 6mm to 24mm covers the majority of fasteners in automotive, construction, and industrial maintenance work. What to look for: Chrome-vanadium steel (Cr-V) construction, clearly stamped sizes, 12-point bi-hex ring profile, chrome-plate finish for corrosion resistance. 4. Adjustable Spanner (Shifter) The shifter has one fixed jaw and one moveable jaw adjusted via a knurled worm gear. Common Australian sizes are 150mm, 200mm, 250mm, and 300mm — these refer to overall tool length, not jaw capacity. Overall Length Max Jaw Opening Common Use Range 150mm (6") ~22mm M6–M12 equivalent 200mm (8") ~28mm M6–M16 equivalent 250mm (10") ~34mm M10–M20 equivalent 300mm (12") ~42mm M16–M27, larger plumbing Critical technique: Always position the shifter so the pulling force acts on the fixed (lower) jaw. When force acts toward the moveable jaw, it spreads under load and slips off the fastener. Close the jaw snugly to zero play before applying torque, and re-snug every few turns during sustained use. ⚠️ Warning: Always pull toward the fixed jaw. Applying torque toward the moveable jaw causes it to spread under load, slip off the fastener, and round the corners — often suddenly and forcefully. Most shifters have a directional arrow stamped on the body. Follow it. Best for: Non-standard fastener sizes, large plumbing fittings, site work where carrying a full fixed spanner set is impractical. Not appropriate for critical or high-torque fasteners. For a complete guide, see our Adjustable Spanner & Shifter Guide — types, sizes, jaw opening table, and correct use technique. 5. Socket Wrench and Ratchet Handle A socket system separates the driving mechanism from the fastener engagement. Sockets clip onto a square-drive ratchet handle via a spring-loaded detent. Drive size determines both torque capacity and ratchet head bulk. Drive Size Fastener Range Approx. Max Torque Primary Application 1/4" (6.35mm) M4–M8 ~30–40 Nm Electronics, interior trim, small precision work 3/8" (9.5mm) M6–M16 ~80–120 Nm General automotive and workshop maintenance — most versatile 1/2" (12.7mm) M10–M24 ~200–600 Nm Wheel nuts, suspension, heavy industrial M12–M24 3/4" (19.05mm) M20–M36 ~800–1,500 Nm Heavy plant, trucks, large flanged pipework 1" (25.4mm) M30+ ~2,000 Nm+ Mining, crane assembly, heavy industrial structures Six-point sockets are preferred for high-torque and damaged fasteners — better load distribution per flat. Twelve-point allows more entry angles and suits tight spaces at the expense of some contact area per flat. Use deep sockets for nuts on long studs or bolts in recessed holes. A breaker bar — not the torque wrench — is the correct handle for break-out. For a complete size reference, see our Spanner & Socket Size Chart. 6. Ratchet Spanner A ratchet spanner looks like a standard combination spanner but incorporates a ratchet mechanism in the ring end. The ring drives in one direction and free-spins on the return stroke — the tool never needs to be lifted and repositioned. Most have a reversing switch for direction change. Best for: Confined spaces where a socket ratchet handle is too bulky but repeated short-stroke tightening is needed — engine bays, control panels, panel-mount assemblies. Fine-tooth ratchets (72-tooth and above) are preferred for very tight spaces where only a few degrees of swing are available. Limitation: The ratchet mechanism reduces peak break-out torque compared to a solid ring. Use a conventional ring for break-out on seized fasteners, then switch to the ratchet spanner for run-down and tightening. For a complete guide, see our Ratchet Spanner Guide — types, tooth count, flex head vs fixed head, and break-out tips. 7. Torque Wrench A torque wrench is a precision measuring instrument that applies a specified, quantified torque to a fastener. It is not a general-purpose tool — it exists to ensure critical fasteners are tightened to the manufacturer's specification, preventing both loosening and overtightening damage. Types in common Australian use: Click-type (micrometer): Set the desired torque; the wrench clicks and releases when reached. Most common in trade. Available in 1/4", 3/8", and 1/2" drive. Typical accuracy ±4% in the upper 80% of range. Beam-type: A needle deflects against a scale as torque is applied. Simple, accurate, durable — no calibration loss. Requires visual confirmation during use. Digital/electronic: Strain gauge with digital readout and programmable alerts. High accuracy (±1–2%). Used in production and calibration-critical environments. Torque-angle: Applies initial torque then rotates a specified additional angle. Required for torque-to-yield (TTY) stretch bolts — modern cylinder head and con-rod bolts. ⚠️ Warning: Never use a click-type torque wrench as a breaker bar. Applying break-out force damages the internal spring mechanism and invalidates calibration. Keep a dedicated breaker bar for break-out. Also return the torque setting to minimum after use to prevent spring fatigue. For full torque wrench type comparison, drive selection, and calibration intervals, see our guides: Torque Wrench Selection Guide and Torque Wrench Calibration Guide. 8. Flare Nut Spanner (Line Spanner) A flare nut spanner is a ring spanner with a slot cut in one side. The slot allows the tool to slide sideways over a pipe and seat around the fitting nut — providing near-full ring engagement on the nut without needing to thread the tool over the end of the tube. Why it exists: Brake, fuel, hydraulic, and air conditioning lines have fitting nuts at the end of a rigid tube. A full ring cannot thread over the tube. An open-end spanner fits but provides only two-point contact — enough to round the soft fitting nuts these lines use. The flare nut spanner provides ring-level grip with open-end access. Common AU applications: Brake line unions (M10×1.0, M12×1.0 in metric AU vehicles), fuel line fittings, A/C refrigerant line connections, hydraulic instrumentation tubing. A socket-drive crow foot version allows torque wrench use on these fittings. 💡 Pro Tip: Never use an open-end spanner on brake or fuel line fittings if a flare nut spanner is available. The fitting nuts are made from soft steel or copper-nickel alloy and round extremely easily. A rounded brake line fitting requires cutting the line and fitting a new end — not a repair that belongs on the side of a road. 9. Pipe Wrench (Stillson) A pipe wrench — called a Stillson in Australia — has a spring-loaded jaw with serrated hardened teeth designed to grip round pipe. The jaw tightens its bite as torque is applied in the working direction. Pipe wrenches grip by biting into and slightly deforming the workpiece surface — they will mark any surface they contact. Suitable materials only: Black steel pipe, galvanised steel pipe. Not suitable for chrome or decorative fittings, copper, aluminium, brass fixtures, or precision-machined surfaces. The teeth will scar these surfaces permanently. Wrench Length Pipe Capacity (OD) Common Application 200mm (8") Up to ~20mm OD Small bore plumbing, hydraulic steel tube 300mm (12") Up to ~40mm OD DN25–DN32 steel pipe — compressed air and commercial plumbing 450mm (18") Up to ~65mm OD DN50 and larger industrial pipework 600mm (24") Up to ~90mm OD Large bore steel mains 10. Allen Key (Hex Key) An Allen key — also called a hex key or hex wrench — is an L-shaped or T-shaped tool with a hexagonal cross-section, used to drive socket-head cap screws (SHCS), button heads, and grub screws. Common forms: L-shape: Short arm for torque, long arm for reach. Most common form for trade use. T-handle: Fast for run-down. Not appropriate for final torque — overtightening strips the internal hex recess. Ball-end: Allows engagement up to ~25° off-axis. Use for run-down only — full flat-face engagement required for final torque. Hex bit sockets: Hex key inserts for standard drive ratchets or impact tools. Most efficient for production and maintenance work. Metric vs imperial in Australia: Metric hex keys (1.5–12mm) are the primary standard. The 4mm, 5mm, and 6mm sizes are most commonly encountered. Imperial hex keys (3/32"–3/8") are needed for American-specification equipment and some imported power tools. 11. Impact Wrench (Rattle Gun) In Australian trade vernacular, an impact wrench is universally called a rattle gun. It delivers high torque through rapid rotary hammer impacts (typically 1,000–3,200 impacts per minute) rather than continuous rotation. Each impact delivers a high-energy rotational jolt — the accumulative effect produces torques far beyond continuous motor output, with minimal reaction force felt by the operator. Pneumatic vs battery-powered: Pneumatic tools are lighter for a given torque output and lower cost, but require a compressor and fixed air supply — best for workshops. Modern 18V/20V brushless battery tools match quality pneumatic output and go anywhere — best for site and field work. Best for: Wheel nuts, structural bolting (M16+), high-volume fastener removal, and breaking seized fasteners where a breaker bar creates excessive reaction force. ⚠️ Warning: Chrome sockets must never be used with impact tools. Standard chrome-finish sockets are not rated for the sudden high-energy hammer loads of an impact wrench. Chrome sockets can shatter at impact loads, sending fragments at high velocity. Always use impact-rated (black phosphate finish) sockets with rattle guns. This is a safety requirement, not a preference. 12. Scaffold Spanner (Podger) A scaffold spanner — called a podger or podger wrench — combines a fixed spanner head (typically 21mm for AU Kwikstage and Ringlock coupler nuts) with a tapered alignment spike (podger) on the opposite end. The spike aligns bolt holes in scaffolding components before the bolt is inserted; the spanner end tightens the coupler nut. One tool handles both alignment and fastening — critical when working at height where additional tools are dropped-object hazards. 13. Strap Wrench A strap wrench uses a flexible loop of rubber, nylon webbing, or chain attached to a rigid handle. The loop grips through friction across the surface of the workpiece — no jaw contact, no edge loading. Best for: Oil filter removal and installation (no canister piercing); chrome-plated plumbing fittings that must not be scratched; round pipe nipples and smooth cylindrical surfaces with no machined flats; PVC or thin-wall plastic components where jaw pressure would crack the material. Limitation: Friction grip fails on wet or oily surfaces. Rubber or chain-type strap wrenches give better grip on oily filters than nylon webbing. Spanner Types Comparison Table Type Contact Points Torque Capacity Best Application Key Limitation Open-end 2 flats Light–medium Quick access, pipe fittings, confined spaces Rounds fasteners under high torque Ring (box end) 6 or 12 points High High torque, corroded fasteners Cannot pass over pipe; needs overhead clearance Combination Both Medium–high General trade and maintenance Compromises of each end type apply Adjustable (shifter) 2–4 flats Medium Non-standard sizes, plumbing, site work Jaw flex; slips if direction is reversed Socket + ratchet 6 or 12 points Very high Production work, recessed fasteners, studs Requires overhead clearance for socket depth Ratchet spanner 12 points Medium Confined repetitive fastening Reduced break-out torque vs solid ring Torque wrench Square drive Precision measurement Critical fasteners to specification Calibration instrument — not a general tool Flare nut (line) 4–5 points Medium–high Brake, fuel, hydraulic line fittings Slotted ring is weaker than solid ring Pipe wrench (Stillson) Serrated bite Very high Steel pipe and round stock Marks all surfaces; chrome and soft metals unsuitable Allen key (hex key) Full hex face Low–medium Socket head cap screws, grub screws Strips internal hex socket on overtightening Impact wrench (rattle gun) Square drive + impact Extreme (powered) High-volume and high-torque fastening Requires impact sockets; no precise torque control Scaffold/podger 6 points + alignment spike Medium–high Scaffolding and structural steel erection Specialised — not a general workshop tool Strap wrench Friction (surface) Low–medium Round surfaces, chrome fittings, oil filters Slips on wet or oily surfaces Metric Spanner Sizes: What Fits What In Australia, the overwhelming majority of fasteners are metric. The correct spanner for any hex fastener is determined by its AF (Across Flats) measurement — the distance between two parallel opposite faces of the hex head. This is the number stamped on every spanner. The approximate rule for standard metric hex fasteners is AF ≈ bolt diameter × 1.7. Bolt Size Standard AF Spanner Required Common Application M4 7mm 7mm Electronics, instrument mounting M5 8mm 8mm Light assemblies M6 10mm 10mm Most common general fastener — guards, automotive trim, brackets M8 13mm 13mm Engine covers, motor mounting, medium structural M10 17mm 17mm Heavy equipment bolting, automotive chassis, machinery frames M12 19mm 19mm Structural steelwork, flanged pipe connections M14 22mm 22mm Heavy plant, agricultural equipment, trailer hitches M16 24mm 24mm Structural bolting Grade 8.8, crane components M20 30mm 30mm Heavy structural bolting, large machinery mounting M24 36mm 36mm Very heavy structural and industrial applications M30 46mm 46mm Mining equipment, bridge and heavy civil structures 📌 Key Fact: The AF dimensions for metric hex fasteners are fixed by ISO 4014 (bolts) and ISO 4032 (nuts). For Grade 8.8 structural fasteners per AS/NZS 1110, the AF dimensions match the ISO standard — M10 = 17mm, M12 = 19mm, M16 = 24mm, M20 = 30mm. These are consistent across all compliant manufacturers. For a printable metric, imperial, and BSP spanner reference, see our Spanner Size Chart — Metric, Imperial & BSP. Metric vs Imperial Spanners in Australia Australia completed its metric conversion progressively through the 1970s and 1980s. Metric is now the dominant standard across automotive, construction, manufacturing, and engineering. Imperial fasteners have not disappeared entirely — they appear in specific sectors and equipment types. Where metric is the exclusive standard: All Japanese, Korean, European, and post-1980 Australian vehicles; all modern industrial machinery to ISO/DIN/AS standards; all Australian construction hardware (AS 1110, AS 1112). Where imperial is still encountered: American agricultural equipment: Many US tractor and implement brands — John Deere, Case IH, Agco — maintain SAE imperial fasteners on chassis and drivetrain components through to recent models. Any AU farm workshop servicing US-brand machinery needs a complete imperial set. Pre-metric vehicles: Classic and vintage Australian vehicles built before the mid-1970s (pre-metric Holden, Ford, Chrysler AU) use imperial AF sizes throughout. Imported American industrial machinery: Compressors, pumps, conveyors from US manufacturers commonly use SAE fasteners throughout regardless of import date. ℹ️ Note: Metric and imperial spanners are not interchangeable. Common near-mismatches include 19mm vs 3/4" (19.05mm) and 22mm vs 7/8" (22.23mm). On a clean fastener the difference may feel minor — on a corroded fastener under torque, even 0.2mm of slop will begin rounding the corners. When in doubt, measure the AF with a calliper before selecting the tool. How to Read a Spanner Size Every spanner is marked with its size. Understanding what the number means depends on the tool type: Open-end, ring, combination spanners: The stamped number (e.g. 17) is the AF in millimetres — the jaw width matching the across-flats measurement of the hex fastener head. Adjustable spanner (shifter): The number is the overall tool length in millimetres (150, 200, 250, 300), not the jaw opening capacity. Sockets: The socket size is the AF of the fastener it fits. The drive size (stamped on the square drive hole) indicates which ratchet it attaches to. Allen keys (hex keys): The number is the across-flats width of the hexagonal key shank — must match the fastener recess exactly. Pipe wrenches: The size refers to maximum recommended pipe diameter capacity, not the tool length. 📌 Key Fact: AF stands for Across Flats — the perpendicular distance between two opposite parallel faces of a hex head fastener. It is the universal standard for specifying spanner, socket, and hex key sizes. For standard ISO metric hex bolts: M6 = 10mm AF, M8 = 13mm, M10 = 17mm, M12 = 19mm, M16 = 24mm, M20 = 30mm. These are fixed by international standard regardless of manufacturer or country of origin. How to Choose the Right Spanner The right spanner depends on more than whether it fits the fastener head. Work through these five checks before picking up any tool: 1. Confirm metric or imperial. Measure the AF with a calliper if uncertain. A 19mm spanner on a 3/4" bolt (19.05mm AF) appears to seat — under break-out torque it will round the corners. 2. Assess the torque required. Run-down and light snug: open-end, Allen key, ratchet spanner. Standard assembly: combination ring end or socket ratchet. High torque — structural or mechanical joints: ring spanner or 1/2" drive socket with breaker bar. Manufacturer-specified torque: torque wrench — look up the spec, set the wrench, do not guess. Extreme torque or seized fastener: impact wrench with impact sockets. 3. Assess access constraints. Open access: choose by torque requirement. Restricted swing arc: ratchet spanner or flex-head socket ratchet. Limited overhead clearance: low-profile socket or offset ring spanner. Fastener on a pipe end: flare nut spanner or open-end. Round surface with no flats: pipe wrench (steel) or strap wrench (soft/polished). 4. Assess fastener condition. New, clean: any correctly-sized tool at the right torque level. Corroded or overtightened: ring spanner or socket only — maximum contact area. Partially rounded: use a socket or ring first; if still slipping, a damaged-bolt extractor socket. Completely rounded: nut splitter, vice-grips, or controlled cutting as a last resort. 5. Confirm precision requirements. Standard assembly: firm hand-tight-plus using ring end or socket. Manufacturer torque specification: torque wrench — non-negotiable for critical joints. Common Spanner Mistakes to Avoid Rounding fasteners with an open-end under high torque. Two-point contact concentrates force and rounds corners. Use a ring or socket for break-out and final torque. Switch to open-end only for run-down once the fastener is moving freely. Using a shifter in the wrong direction. Force toward the moveable jaw causes it to spread and slip. Check the direction arrow before applying force. Using a close-but-wrong size. 14mm open-end on a 9/16" bolt (14.3mm AF) appears to seat. Under torque, the 0.3mm difference rounds the corners. Measure with a calliper when uncertain. Pushing instead of pulling. Where possible, pull a spanner toward the body. If the tool slips while pushing, knuckles impact the nearest sharp metal surface. Pulling provides more control and reduces injury risk. Cheater bars on standard spanners. Extending a spanner handle with a pipe to gain more leverage is dangerous — the tool is not rated for the torque achievable. If more torque is needed, use a tool rated for the load: longer handle, breaker bar, or impact wrench. Using a torque wrench as a breaker bar. Break-out force damages the internal spring mechanism and invalidates calibration permanently. Keep a dedicated breaker bar for break-out. The torque wrench enters the sequence only after the fastener is already moving. Chrome sockets on impact tools. This is a safety requirement, not a preference. Chrome sockets can shatter under impact loads. Use black impact sockets with rattle guns exclusively. Spanner Safety — Australian Standards In Australian workplaces, hand tool use falls under general duty obligations in the Work Health and Safety Act 2011 and corresponding state legislation. The relevant manufacturing and quality standard for manually-operated spanners is AS/NZS 1700 — Hand Tools: Spanners and Wrenches, which covers dimensional, material, and marking requirements for tools sold in Australia and New Zealand. Pre-use inspection: Check open-end jaw faces for rounding or spreading. Inspect ring internal profiles for wear (oval profile loses engagement). Look for cracks at the jaw root and ring-to-handle junction. Check adjustable spanner worm gear for grit or corrosion. Remove any damaged tool from service immediately. Storage and maintenance: Chrome-vanadium spanners resist corrosion well but benefit from a light oil wipe after wet or marine environment use. Store in roll pouches, shadow boards, or foam-lined drawers — loose storage causes nicks and burrs on jaw faces. In scaffolding and elevated work, tool tethering is required under WHS regulations. 💡 Pro Tip: In any workshop with high fastener volumes, a shadow board with a painted outline for each spanner size delivers faster tool selection, instant visibility of missing tools, and a controlled tool management system for workplace audits. The setup cost is low; the compound benefit over years of use is significant. The right spanner for every job. Shop combination, ring, open-end & torque spanners from Stahlwille & more AIMS Industrial stocks a comprehensive range of spanners, wrenches, and socket sets for trade, workshop, and industrial use — combination spanner sets, adjustable shifters, scaffold podgers, torque wrenches, flare nut sets, and impact socket sets. Browse spanners & wrenches Talk to a specialist Frequently Asked Questions What is the difference between a spanner and a wrench? In Australian and British usage, the tool is called a spanner. In American usage, the same tool is called a wrench. They refer to the same thing — the names differ by region. In Australia, spanner is the correct trade term. Some specific tools retain "wrench" in their name — torque wrench, pipe wrench, and impact wrench are all standard Australian terminology. In casual conversation "wrench" is understood, but in trade settings "spanner" is correct. What is the most versatile spanner for general trade work in Australia? The combination spanner is the standard workhorse for Australian trade work. It combines an open-end jaw for fast run-down with a ring end for high-torque tightening on the same tool at the same size. A quality metric combination spanner set from 6mm to 24mm covers the majority of fasteners encountered in automotive, construction, and industrial maintenance. This is the correct starting point for any trade toolkit. What does shifter mean in Australian trade terminology? Shifter is the Australian colloquial term for an adjustable spanner — one with a fixed jaw and a moveable jaw adjusted via a worm gear to fit different fastener sizes. It is not a generic term for all spanners. Common sizes are 150mm, 200mm, 250mm, and 300mm, where the number is the overall tool length, not the jaw opening capacity. How do I read the size marked on a spanner? For open-end, ring, and combination spanners, the stamped number such as 17 is the AF (Across Flats) measurement in millimetres — the jaw width corresponding to the flat-to-flat dimension of the hex fastener head. A 17mm spanner fits a 17mm AF fastener, which is a standard M10 bolt. For adjustable spanners the number is the overall tool length. For Allen keys the number is the across-flats width of the hex key shank itself. What is the difference between an open-end and a ring spanner? An open-end spanner grips two opposite flats of a hex fastener using a U-shaped jaw. It is fast to position but contacts only two faces, making it prone to slipping and rounding the fastener under high torque. A ring spanner has a fully enclosed circular head engaging all six faces simultaneously, providing maximum grip and torque capacity. The ring is the correct choice for high torque or corroded fasteners. The open-end is correct for run-down speed and access in spaces where a ring cannot fit. Combination spanners carry both. Can I use an adjustable spanner instead of a fixed spanner? Yes, but it should not be the preferred choice. A shifter is most useful when the correct fixed spanner is unavailable, for non-standard fastener sizes, or for large plumbing fittings. The moveable jaw introduces flex that increases the risk of slipping and rounding the fastener, particularly under high torque. Load must always be applied toward the fixed jaw — not the moveable jaw. Whenever the correct fixed spanner is available, use it. What spanner fits an M10 bolt? An M10 bolt has a standard AF of 17mm under ISO 4014. A 17mm spanner or socket is the correct tool. The approximate rule for standard metric fasteners is AF equals bolt diameter multiplied by 1.7, giving 17mm for M10. When uncertain, measure the AF directly with a vernier calliper — some fastener types and grades use non-standard AF dimensions. Why do most ring spanners have 12 points rather than 6? A 12-point (bi-hexagonal) ring can be repositioned every 15 degrees of swing, compared to 30 degrees for a 6-point ring. In confined spaces with a limited swing arc, this halves the repositioning lifts needed per full fastener rotation. Six-point rings distribute force over more of each fastener face and are preferred for very high torque or damaged fasteners. In practice, 12-point is the standard for general use and 6-point is specified for maximum-torque situations. What is a ratchet spanner and when is it the right tool? A ratchet spanner has a ratchet mechanism in the ring end that drives the fastener in one direction and free-spins on the return stroke, eliminating the need to reposition the tool between strokes. It is correct in confined spaces where a socket ratchet handle is too bulky but repeated short-stroke tightening is needed. It is not the right tool for initial break-out on a seized fastener — the mechanism reduces peak torque. Use a conventional ring for break-out, then switch to the ratchet spanner for run-down. How do I choose between 1/4 inch, 3/8 inch, and 1/2 inch drive socket sets? Drive size determines torque capacity and ratchet head size. A 1/4 inch drive suits M4 to M8 fasteners and light precision work. A 3/8 inch drive is the most versatile and the recommended starting point, covering M6 to M16 and handling 80 to 120 Nm comfortably. A 1/2 inch drive is needed for M12 to M24 fasteners, wheel nuts, and heavy industrial work, handling 200 to 600 Nm manually. Most workshops carry all three, with the 3/8 inch set doing the majority of everyday work. What is a flare nut spanner and when must I use one? A flare nut spanner is a ring spanner with a slot cut in one side, allowing it to slide sideways over a pipe and engage the fitting nut at the tube end. It provides near-full ring engagement on the nut — far superior to an open-end spanner. It must be used on brake, fuel, hydraulic, and air conditioning line fittings where a full ring cannot thread over the tube. These fitting nuts are made from soft materials and round extremely easily with an open-end spanner. A rounded brake line fitting requires cutting the line and fitting a new end. What type of spanner is correct for scaffolding work in Australia? A scaffold spanner, also called a podger spanner, is the correct tool. It combines a fixed spanner head — typically 21mm for the Kwikstage and Ringlock coupler nuts used in the dominant Australian scaffolding systems — with a tapered alignment spike (podger) on the opposite end. The podger aligns bolt holes before the bolt is inserted; the spanner end tightens the coupler nut. A standard 21mm combination spanner does not include the alignment spike and is not a substitute. For metric to imperial socket cross-references and 1/4", 3/8" and 1/2" drive sizes, see our Socket Size Chart. Cross-reference our Metric Bolt Size Guide when working with metric M-series fasteners. What spanner size do I need for a wheel nut? Most Australian passenger cars use 19mm or 21mm wheel nuts, while light commercial vehicles and 4WDs often use 22mm or 24mm. Check the wheel nut directly with the spanner before buying a set. A 1/2 inch drive socket and breaker bar is the correct tool for wheel nut work — a torque wrench is then used to finalise the nut to manufacturer specification. What's the difference between a socket and a spanner? A socket is a separate hex-shaped cup that drives onto a ratchet handle via a square-drive connection. A spanner is a one-piece tool with the hex grip and handle integrated. Sockets allow one handle to swap between dozens of fastener sizes and are faster for repetitive work, while spanners are faster to grab for a single fastener and work in tight spaces where a ratchet head won't fit. Are wrench and spanner sizes the same? Sizes themselves use the same Across Flats measurement, but the labelling differs. Australian and UK spanners are marked in millimetres for metric fasteners. American wrenches are typically marked in fractional inches for imperial fasteners. A 19mm metric spanner is close to but not the same as a 3/4 inch wrench — 19.05mm — and using one in place of the other will round a fastener under load. Need adjustable hand reamers? Browse the AIMS range at adjustable hand reamers. AIMS Industrial stocks open end wrenches — see the full range for trade and industrial use.
Read moreTap & Die Guide: Cutting Threads
How to Cut Threads with a Tap & Die — Quick Reference The seven-step process for cutting accurate threads using hand taps and dies. Select the correct tap drill size — match the drill diameter to the tap from a tap drill chart (e.g. M6 × 1.0 = 5.0 mm drill). Drill the pilot hole square and clean — use cutting fluid; deburr both sides of the hole. Use cutting fluid — never tap dry. Cutting fluid prevents tap breakage and gives clean threads. Start with a taper tap — 7–10 cutting threads on the leading edge to ease into the hole. Turn forward two turns, then back a quarter turn — clears chips and prevents binding. Repeat for full depth. For blind holes, finish with a bottoming tap — fewer leading threads, cuts to the bottom of the hole. For external threads, use a die with a die stock — keep square to the work, apply cutting fluid, same forward-back rhythm. Set this aside as your basic tapping procedure. The detailed sections below cover drill size selection, tap types, common problems and recovery from broken taps. Tap & Die Set Guide: How to Tap Threads & Cut Externals A tap and die set is the standard tool for cutting internal and external screw threads by hand. A tap cuts the female thread inside a drilled hole; a die cuts the male thread onto a rod or bolt shank. Together they cover thread creation, thread repair, and thread restoration across the full range of metric, imperial, and pipe thread standards used in Australian industry, automotive, engineering, and maintenance work. This guide covers how both tools work, how to select the correct drill size before you tap (this is where most threads fail), which tap type to use for through holes versus blind holes, how to cut external threads cleanly, how to choose the right lubricant for the material you are threading, the difference between thread cutting and thread chasing, and the root causes of broken taps and how to prevent them. Contents What are taps and dies? Types of taps: taper, plug, and bottoming Thread standards in Australia Tap drill size: the critical first step How to tap a thread (step by step) How to cut external threads with a die Lubrication by material Thread chasing vs thread cutting Common mistakes and broken taps Frequently asked questions What are taps and dies? A tap is a fluted, hardened steel tool used to cut internal threads inside a pre-drilled hole. The flutes run along the length of the tap body; they provide the cutting edges and allow chips to escape during cutting. The tap is rotated into the hole using a tap wrench or T-handle, and it removes material in a helical pattern to form the thread profile. A die is a hardened circular tool with a central threaded aperture and cutting edges around its inside diameter. It is held in a die stock (a handle with a central hole to seat the die). The die is placed over the end of a rod or bolt shank and rotated to cut an external thread. Most dies are split and adjustable — a small screw allows the aperture to be opened slightly for a first rough pass and then closed to final size for a finishing pass. The tap cuts the nut; the die cuts the bolt. That is the simplest way to remember which does what. Taps and dies are made from one of three materials, depending on application and price point: High-speed steel (HSS): The standard for industrial and professional use. Suitable for steel, aluminium, brass, cast iron, and most engineering materials. Resharpening is possible. HSS is the correct choice for serious workshop use. Carbon steel: Found in cheaper consumer-grade sets. Adequate for occasional soft material use (aluminium, brass, plastic). Unsuitable for stainless steel or repeated hard steel use. Edge life is substantially shorter than HSS. HSS-Co (cobalt HSS): Premium grade for stainless steel, titanium, and high-alloy steels. Higher cost, significantly better performance in hard or abrasive materials. Types of taps: taper, plug, and bottoming Hand taps are produced in three configurations that differ in the amount of lead chamfer — the tapered section at the tip that begins the cutting action. Selecting the correct type for the job prevents the most common beginner failures. Taper tap (also called starting tap) A taper tap has 7–10 threads chamfered at the tip, creating a long, gradual entry. The extended lead distributes cutting load over many teeth, making the tap easy to start square and reducing torque at entry. Taper taps are the correct first choice for starting new threads in any unthreaded hole. They work well in through holes and are forgiving of minor misalignment at the start. Limitation: The long chamfer means the taper tap cannot thread to within 7–10 thread pitches of the bottom of a blind hole. For blind holes requiring full-depth threads, a plug or bottoming tap must follow. Plug tap (also called second tap or intermediate tap) A plug tap has 3–5 chamfered threads at the tip. It can start in an unthreaded hole (useful when a taper tap is not available), cuts threads closer to the bottom of a blind hole than a taper tap, and is the most common general-purpose tap included in standard sets. If a tap and die set includes only one tap per size, it is almost always a plug tap. For most through-hole tapping applications, a plug tap alone is sufficient. For blind holes, use a taper tap first to establish the thread, then follow with a plug tap to deepen it. Bottoming tap (also called third tap or bottom tap) A bottoming tap has only 1–2 chamfered threads. It cannot start in an unthreaded hole — attempting to do so is a reliable way to break the tap. Its sole purpose is to extend threads to within 1–2 pitches of the bottom of a blind hole after a taper and/or plug tap has already cut the thread. If your application requires full-depth threading in a blind hole, the correct sequence is: taper tap → plug tap → bottoming tap. Skipping to the bottoming tap immediately is the single most common cause of tap breakage among beginners. ✅ Which tap to use: quick reference Through hole: Plug tap alone is sufficient. Taper tap first if you want easiest starting. Blind hole, partial depth: Taper tap → plug tap. Blind hole, full depth to bottom: Taper tap → plug tap → bottoming tap. Spiral point (gun) taps Spiral point taps have a modified cutting face that pushes chips forward and down through the hole rather than evacuating them backward. They are faster than hand taps in through holes and are the standard choice for machine tapping. They are not suitable for blind holes — chips pushed to the bottom have nowhere to go and will cause jamming. Spiral flute taps Spiral flute taps have helical flutes that pull chips up and out of the hole, away from the cutting zone. They are the correct choice for blind holes in machine tapping, and are particularly effective in soft, stringy materials like aluminium and stainless steel. Not common in hand tap sets but worth knowing about for production applications. Thread standards in Australia Australia uses three thread standard families in everyday industrial, mechanical, and plumbing applications. Buying the right set and selecting the right tap for the job requires understanding which standard applies to your application. Metric (M) threads The dominant thread standard for fasteners in Australia. All modern machinery, automotive, structural, and most engineering fasteners use metric threads. Metric threads are defined by nominal diameter and pitch: M8×1.25 means 8 mm major diameter, 1.25 mm between thread crests. Coarse pitch is the standard for most fastener applications; fine pitch (e.g., M8×1.0) is used where vibration resistance, thin-wall material, or precise adjustment is required. A metric coarse tap and die set covering M3 to M12 handles the overwhelming majority of general workshop work. Sets extending to M20 cover structural, heavy engineering, and automotive applications. BSP (British Standard Pipe) threads BSP threads are standard for pipe fittings, hydraulic connections, pneumatic fittings, and plumbing in Australia and New Zealand. BSP uses a 55° thread angle (compared to 60° for metric) and thread pitch defined in threads per inch. Two variants exist: BSPP (BSP parallel, also called G thread): Both male and female threads are parallel. The seal is made by a bonded seal washer (Dowty seal) or O-ring at the face, not by the threads. Most common in hydraulic and pneumatic fittings. BSPT (BSP taper): The male thread is tapered (1:16 taper). Sealing is achieved by the taper interference, often supplemented by PTFE tape. Common in plumbing and gas applications. BSP sizes are nominal pipe sizes, not actual thread diameters: a ½" BSP fitting has an actual thread OD of approximately 20.96 mm — considerably larger than ½". This causes persistent confusion when measuring. A dedicated BSP tap and die set is needed for pipe thread work; metric taps will not cut BSP threads even if the diameter appears similar. UNC / UNF imperial threads Unified National Coarse (UNC) and Unified National Fine (UNF) threads are the standard for imperial fasteners, predominantly found in older Australian equipment, American-made machinery, and imported automotive components. UNC/UNF uses a 60° thread angle (same as metric) but pitch is defined in threads per inch rather than millimetres. A ⅜"-16 UNC fastener has a ⅜" major diameter and 16 threads per inch. If your application involves older equipment, American vehicles, or any fastener sold in fractional inch sizing, you need an imperial tap and die set. Metric and imperial taps will not interchange — do not attempt to run an M10 tap into a thread started by a ⅜"-16 die. Tap drill size: the critical first step The most common cause of failed threads — weak engagement, tap breakage, torn threads — is an incorrectly sized pilot hole. Too small, and the tap must remove too much material: cutting torque rises sharply, and the tap breaks or the hole strips. Too large, and thread engagement is shallow: the resulting thread is weak and will strip under load. The standard tap drill size gives approximately 75% thread engagement — the industry benchmark that balances thread strength against cutting torque. At 75% engagement, the thread achieves approximately 98% of the strength of full (100%) thread engagement, while cutting torque is manageable. Going to 65% engagement (0.1–0.2 mm larger drill) is common practice for hard materials (stainless steel, titanium, high-tensile alloys) where reducing tap breakage risk outweighs the marginal strength reduction. Tap drill formula (metric): Tap drill diameter = Nominal diameter − Pitch Example: M10×1.5 → tap drill = 10 − 1.5 = 8.5 mm The following table covers the metric coarse thread sizes most commonly tapped in workshop practice, plus key BSP sizes: Thread size Pitch (mm) Standard tap drill (75% engagement) Reduced engagement drill (65%, hard materials) M3 0.5 2.5 mm 2.6 mm M4 0.7 3.3 mm 3.4 mm M5 0.8 4.2 mm 4.3 mm M6 1.0 5.0 mm 5.1 mm M8 1.25 6.8 mm 6.9 mm M10 1.5 8.5 mm 8.7 mm M12 1.75 10.2 mm 10.4 mm M14 2.0 12.0 mm 12.2 mm M16 2.0 14.0 mm 14.2 mm M20 2.5 17.5 mm 17.7 mm ¼" BSP (BSPP/BSPT) 19 TPI 11.8 mm — ⅜" BSP 19 TPI 15.3 mm — ½" BSP 14 TPI 19.1 mm — ¾" BSP 14 TPI 24.5 mm — 1" BSP 11 TPI 30.5 mm — Always verify tap drill size against the specific tap manufacturer's data before drilling. Variations of ±0.1 mm exist between standards. For critical applications, consult the tap manufacturer's drill size recommendation. How to tap a thread (step by step) Step 1: Mark and centre-punch the hole location Accuracy at this step determines alignment through the entire process. Use a centre punch to dimple the surface at the exact hole location before drilling. The dimple prevents the drill from walking off position and ensures the hole starts where intended. Step 2: Drill the pilot hole to the correct size Use the tap drill size from the table above. Drill the hole square to the surface — a drill press is strongly preferred over a handheld drill for critical applications. Misalignment of even 1–2° will be magnified through the tapping process and produce a crooked thread. For blind holes: drill to a depth equal to the required thread depth plus 3–5 thread pitches of clearance. The tap needs space beyond the thread zone to avoid bottoming out. Mark the required depth on the drill bit with tape. Step 3: Deburr the hole entry After drilling, use a larger drill bit or countersink (held by hand and rotated) to chamfer the top edge of the hole lightly. This removes the sharp burr raised by drilling, provides a lead-in for the tap, and prevents the first thread from being raised above the surface — a common cause of nut/bolt interference. Step 4: Apply cutting lubricant Apply lubricant to the tap before entering the hole. Do not dry-tap any material except cast iron and some plastics. See the lubrication section below for material-specific recommendations. Step 5: Start the tap square This is the most critical step. Place the taper tap at the hole entrance and apply gentle downward pressure while rotating slowly clockwise. After the first 1–2 full turns, the tap is threading itself and no further downward pressure is needed — the thread pitch pulls the tap in at the correct rate. Use a small engineer's square held against the tap body and the work surface to verify the tap is entering square. If it is tilted, back the tap out completely and restart. Tapping a crooked thread cannot be corrected once started. Step 6: Use the forward-back chip-breaking rhythm Advance the tap ¾ to 1 full turn forward, then reverse ¼ to ½ turn. The reverse stroke breaks the chip, preventing the chip mass from packing in the flutes and jamming the tap. This rhythm is non-negotiable in any material that produces continuous chips — steel, stainless, aluminium. In brittle materials (cast iron, brass), chips break naturally and the rhythm is less critical but still good practice. Never force a tap. If resistance increases sharply, back the tap out, clear the chips, re-lubricate, and re-enter. Forcing a tight tap is the second most common cause of breakage after misalignment. Step 7: For blind holes, manage depth carefully Back the tap out completely periodically to clear chips from the flutes. In blind holes, chips cannot fall through — they accumulate in the flutes and at the hole bottom. A tap jammed against a chip mass at the bottom of a blind hole will break. Clear chips every 4–5 full rotations in blind holes, more frequently in soft materials that produce long, stringy chips. Step 8: Follow with plug and bottoming taps if required Once the taper tap has completed its depth, follow with a plug tap using the same technique to deepen the thread, and then a bottoming tap if full-depth threading to the hole bottom is required. Re-lubricate between each tap. Step 9: Clean the threaded hole Before installing any fastener, clear the tapped hole of chips and cutting fluid. Compressed air into the hole (wear eye protection), followed by a thread cleaning brush or a bolt with the shank wrapped in a rag, removes residual chips. A chip in the thread will prevent a fastener from seating fully and can strip the thread on installation. How to cut external threads with a die Cutting external threads with a die follows similar principles to tapping — correct preparation, starting square, and the forward-back rhythm — with a few specific differences. Prepare the rod or bar end The rod must be the correct diameter for the thread being cut. For metric threads, the rod diameter should equal the nominal thread diameter within a tolerance of −0.05 to −0.15 mm. A slightly undersize rod produces a correct fit; a rod exactly at nominal diameter may be too tight for the die to start. File or turn a 15–20° chamfer on the end of the rod — this gives the die a lead-in and prevents the die from splitting the first thread. Set the die in the stock Place the die in the die stock with the chamfered (lead) side facing down toward the rod end. Most dies are marked on one face — this marked face faces up in the stock. The three adjustment screws in the stock seat the die centrally. For adjustable split dies, open the die slightly (loosen the centre screw, tighten the two outer screws) for the first rough pass. Start the die square As with tapping, starting square is critical. Place the die flat against the rod end and apply downward pressure while rotating clockwise. If the rod is held in a vice, orient the die stock handles vertically and use them as a visual reference. After 2–3 threads are engaged, the die is self-pulling and no downward pressure is required. Use the forward-back rhythm and lubricate The same ¾ turn forward, ¼ turn back chip-breaking rhythm applies. Lubricate the die and rod throughout. Dies are more susceptible to chip packing than taps because the die surrounds the material — chips have less room to escape. Finish to size After the first rough pass, back off the die and close it to final size by reversing the adjustment (tighten the centre screw, loosen the outer screws). Run the die through again to cut the threads to full depth and proper fit. Check fit with a nut: the nut should thread freely by hand with no perceptible wobble or binding. Lubrication by material Cutting lubrication reduces friction, removes heat, aids chip evacuation, improves thread finish, and extends tool life. "Any oil" is not adequate — the correct lubricant for the material being threaded makes a measurable difference in both tool life and thread quality. Material Recommended lubricant Notes Mild steel Neat cutting oil or sulphurised threading oil Sulphurised oils (e.g., pipe threading oil) are particularly effective for steel — the sulphur reacts with the steel surface to reduce friction. Do not use on copper or brass (stains). Stainless steel Heavy-duty tapping paste or sulphurised oil Stainless work-hardens rapidly when dry. Inadequate lubrication causes the tap to rub rather than cut, generating heat that hardens the surface and seizes the tap. Do not rush, do not dry-tap. Aluminium Kerosene, WD-40, or purpose-made aluminium tapping fluid (Tap Magic) Aluminium is soft and sticky — it loads up in the flutes rapidly without lubrication. Kerosene is the traditional workshop choice. Dedicated aluminium tapping fluids provide better chip evacuation and finish. Cast iron Dry — no lubricant Cast iron is self-lubricating due to its graphite content. Cutting oil can cause chips to clump and jam the tap. Blow chips clear with compressed air between passes. Brass / bronze Light cutting oil or dry Brass cuts freely with or without lubricant. Light oil improves finish. Avoid sulphurised oils — sulphur stains and can react with copper alloys. Titanium / high-alloy steel Heavy sulphurised oil or specialist tapping paste These materials are hard, work-harden aggressively, and generate significant heat. Use HSS-Co taps, reduce engagement to 65%, and apply generous lubrication. Take the chip-break rhythm seriously — taps break easily in titanium. Plastic / nylon Dry or light oil Most plastics tap dry. Some engineering plastics (HDPE, nylon) benefit from a very light oil. Avoid heavy cutting fluids — they can swell or degrade some polymers. Thread chasing vs thread cutting Thread chasing and thread cutting are fundamentally different operations performed by different tools. Confusing them — specifically, using a standard tap or die to "clean up" a damaged thread — is one of the most damaging mistakes in thread repair work. Thread cutting: creating new threads A standard tap or die cuts new threads by removing material to form the thread profile. When used in an unthreaded hole or on an unthreaded rod, this is correct use. When used to "clean" or "restore" a thread that already exists, a standard tap or die removes a small amount of additional material on every pass — leaving the thread slightly oversized on a bolt or undersized in a nut. The result is a loose, weakened thread that will strip more easily than the original. Thread chasing: restoring existing threads A thread chaser is a tool specifically designed to restore damaged or corroded threads without removing material. Chasers have a relieved profile and work by re-forming and cleaning existing thread crests rather than cutting new material. A thread chaser run through a rusty or slightly burred thread restores it to its original profile — the fit with a mating fastener is preserved. For bolt threads, rethreading dies or thread file sets (files with thread profiles on each face) perform the same function on external threads. For nut or tapped hole threads, spark plug thread chasers are common in automotive use; more general thread tap chasers (also sold as "re-tap" tools) are available in metric and BSP. When to use which: Hole with no threads, or thread so badly stripped it needs to be recut → standard tap (consider a thread insert/Helicoil if the material is thin or soft) Existing thread that is corroded, galled, burred, or has a damaged crest → thread chaser Bolt thread that is lightly damaged or has paint/rust buildup → rethreading die or thread file Common mistakes and broken taps Broken taps are the most costly mistake in tapping work — extracting a broken tap from a blind hole in a critical component can be more expensive than replacing the component entirely. All tap breakage has a root cause that could have been prevented. If a tap has already broken, see our Broken Tap Removal Guide for the six recovery methods. If the parent thread itself is damaged from a broken tap, stripped fastener, or repeated cycling, see our Stripped Thread Repair Guide covering Recoil and Helicoil wire inserts, TimeSert solid bushings, and Keysert locking inserts. 1. Wrong pilot hole size Drilling too small is the direct cause of excessive cutting torque. At 75% thread engagement the tap has enough material to cut cleanly; below this, cutting force rises non-linearly and the tap is increasingly likely to seize or snap. Always use a tap drill chart — never estimate the hole size. 2. Misalignment at entry This is the number one cause of tap breakage in precision work. A tap entering even 2–3° off square will be progressively stressed as it advances. The threads on one side are cut deeper than the other; the tap body is placed in bending stress in addition to torsional stress. Use a drill press for pilot holes. Use an engineer's square to verify the tap at entry. A tap guide — a simple jig that holds the tap perpendicular to the surface — is inexpensive and eliminates this failure mode entirely. 3. No chip-breaking rhythm Tapping straight through without reversing — especially in blind holes or with deep cuts in steel — allows chips to pack into the flutes. Packed flutes jam, torque spikes, and the tap breaks. The forward-back rhythm is not optional; it is the technique. 4. Bottoming out in a blind hole A bottoming tap driven to the base of a blind hole with chips still present will shear off cleanly. Know your hole depth, mark the tap with tape at the appropriate depth, and back out to clear chips before reaching the bottom. 5. Inadequate or wrong lubricant Dry tapping in steel or stainless is a reliable way to break a tap quickly. In stainless, the surface work-hardens under the tap's rubbing face within seconds of dry contact. Always lubricate, and use the correct lubricant for the material. 6. Using a worn or damaged tap HSS taps have a finite service life. A tap with chipped cutting edges or worn flute geometry cuts poorly, generates heat, and is structurally weakened. Inspect taps before use under good light. If a cutting edge is chipped or a flute is cracked, discard the tap. The cost of a new tap is always less than the cost of extracting a broken one. ⚠️ If you break a tap in a workpiece Options in order of destructiveness: (1) tap extractor tool — only works on taps not fully broken below the surface; (2) EDM (electrical discharge machining) — the standard professional method for broken taps in critical components; it burns the tap out without affecting the parent material; (3) drilling out — only possible if the tap is smaller than the next drill size that can be accommodated, and even then risks damaging the hole. For broken taps in critical or expensive components, take the part to a machine shop with EDM capability before attempting destructive extraction. Frequently asked questions What is a tap and die set used for? A tap and die set is used to cut screw threads. The tap cuts internal (female) threads inside a drilled hole — allowing a bolt or machine screw to thread into it. The die cuts external (male) threads onto a rod or bolt shank. Together they are used to create new threads, repair stripped or damaged threads, and restore corroded or galled fasteners. Common applications include workshop fabrication, automotive repair, machinery maintenance, and plumbing and pipe fitting work. What is the difference between a taper, plug, and bottoming tap? The three tap types differ in the lead chamfer at the tip. A taper tap has 7–10 chamfered threads — the long lead makes it easy to start square and distributes cutting load, but it cannot thread to within 7–10 pitches of the bottom of a blind hole. A plug tap has 3–5 chamfered threads — it is the general-purpose tap for most jobs. A bottoming tap has only 1–2 chamfered threads — it cannot start in an unthreaded hole but can extend threads to the very bottom of a blind hole after the taper and plug taps have done their work. For blind holes requiring full-depth threads, use all three in sequence: taper, then plug, then bottoming. What size drill do I use before tapping? The tap drill size equals the nominal thread diameter minus the thread pitch for metric coarse threads. Common sizes: M6×1.0 requires a 5.0 mm drill; M8×1.25 requires 6.8 mm; M10×1.5 requires 8.5 mm; M12×1.75 requires 10.2 mm. This gives approximately 75% thread engagement, which is the standard recommended for most materials. For hard materials like stainless steel or titanium, drill 0.1–0.2 mm larger to reduce cutting torque and tap breakage risk — the thread strength reduction is marginal. Always verify with the tap drill chart included with your set or the tap manufacturer's data. What is a BSP tap and die set? A BSP (British Standard Pipe) tap and die set cuts the pipe thread standard used for plumbing, hydraulic, pneumatic, and gas fittings in Australia and New Zealand. BSP threads have a 55° thread angle (unlike the 60° of metric and UNC threads) and pitch measured in threads per inch. BSP taps and dies will not interchange with metric tools even when sizes appear similar. Two BSP types exist: BSPP (parallel, used with a bonded seal or O-ring) and BSPT (tapered, seals by thread interference). A combined BSP set covering ⅛" to 1" handles most workshop and plumbing applications. How do I use a die to cut external threads? Chamfer the rod end at 15–20° to give the die a lead-in. Mount the die in the die stock with the chamfered face of the die toward the rod. Apply cutting fluid. Place the die flat on the rod end and rotate clockwise with gentle downward pressure until 2–3 threads engage — after this the die is self-pulling. Use the forward-back chip-breaking rhythm throughout. For adjustable split dies, run the die open for the first pass, then close to final size and run through again for a correct fit. Check with a mating nut — it should thread freely by hand with no wobble. What lubricant should I use when tapping? The correct lubricant depends on the material: use neat cutting oil or sulphurised threading oil for mild steel; heavy tapping paste or sulphurised oil for stainless steel (which work-hardens rapidly without lubrication); kerosene or a dedicated aluminium tapping fluid for aluminium; no lubricant for cast iron (it is self-lubricating and oil causes chip clumping); light oil or dry for brass and bronze. Do not use water-soluble coolants as a substitute for tapping oil — they are designed for flood cooling, not boundary lubrication under slow sliding contact. What is the difference between thread cutting and thread chasing? Thread cutting creates new threads by removing material. Thread chasing restores existing threads without removing material. Using a standard tap or die to clean up a damaged thread removes additional metal and leaves the thread slightly oversize or undersize, producing a looser, weaker fit than the original. Thread chasers — specifically designed tools with a relieved profile — re-form and clean thread crests without cutting new material, preserving the original thread dimensions. For damaged or corroded threads on existing fasteners and fittings, use a thread chaser, not a standard tap or die. Why do taps break and how do I prevent it? Taps break for six main reasons: pilot hole too small (excessive cutting torque); misalignment at entry (bending stress on the tap body); no chip-breaking rhythm (chips pack and jam); bottoming out in a blind hole; inadequate or wrong lubricant; and using a worn or chipped tap. Prevention: always use the correct tap drill size, verify alignment at entry with an engineer's square, use the forward-back rhythm consistently, mark depth on the tap when working in blind holes, lubricate correctly for the material, and inspect taps before use. These six habits eliminate the vast majority of tap breakage. Can I use metric taps on imperial threads or vice versa? No. Metric and imperial (UNC/UNF) threads have different pitches, different diameters, and the same 60° thread angle — which makes them appear interchangeable but they are not. An M10×1.5 tap and a ⅜"-16 UNC tap are close in diameter (10 mm vs 9.53 mm) but have different pitches and diameter. Starting a metric tap in an imperial thread, or vice versa, will cross-thread and destroy both the tap and the workpiece. Always identify the thread standard before selecting a tap. BSP threads are a further separate standard with a 55° angle — completely non-interchangeable with either metric or UNC. How do I identify an unknown thread? Identifying an unknown thread requires two measurements: the thread pitch and the outside diameter. Use a thread pitch gauge (a set of combs with different pitch profiles) to identify the pitch by finding the comb that fits perfectly with no rocking. Then measure the outside diameter with a vernier calliper or micrometer. With pitch and diameter, cross-reference a thread identification chart to determine the standard and size. For pipe threads, note that BSP nominal sizes do not correspond to actual diameters — a ½" BSP thread has an OD of approximately 21 mm, not 12.7 mm. What is a thread insert and when should I use one? A thread insert (commonly sold as Helicoil or Time-Sert) is a helical coil or solid insert of hardened steel that is fitted into a tapped hole to provide a stronger, more durable thread than the parent material alone. Thread inserts are used when: the parent material is too soft to hold a thread reliably (aluminium, magnesium, plastic); a thread has been stripped and the hole cannot be replaced; a metric thread needs to be added to a location previously held a different thread; or when thread strength must be increased beyond what the parent material can provide. Installing a thread insert requires drilling the hole oversize to a specific insert tap drill, tapping with a special insert tap, and pressing or winding the insert in with an installation tool. Metric or imperial — which tap and die set should I buy? For general Australian workshop use, buy a metric set first. Modern machinery, automotive, structural fasteners, and new fabrication in Australia are overwhelmingly metric. A metric coarse set covering M3 to M12 (or M3 to M20 for heavier work) will handle the majority of applications. If you work on older equipment, American vehicles, or agricultural machinery with imperial fasteners, add a UNC/UNF imperial set. If you do any plumbing, hydraulic, pneumatic, or gas fitting work, a BSP set is essential and cannot be substituted with metric tools. High-quality HSS sets from Sutton Tools (Australian-made), Gearwrench, Irwin, or LPR Toolmakers are appropriate for professional workshop use. Avoid carbon-steel sets for anything beyond occasional soft-material use. AIMS Industrial stocks tap and die sets in metric, imperial, and BSP across professional HSS and HSS-Co grades. For thread repair kits, individual tap sizes, and cutting fluids, contact our team. People Also Ask — Taps and Dies for Thread Cutting Q: What is the difference between a taper tap, plug tap and bottoming tap? All three cut the same thread profile but differ in their starting taper. A taper tap has a long lead taper (7–10 threads), making it the easiest to start in a hole and align correctly — used first to start a thread. A plug tap has a shorter taper (3–5 threads) and is used for general-purpose tapping once started. A bottoming tap has almost no taper and cuts threads to the very bottom of a blind hole. The correct sequence for a blind hole is taper → plug → bottoming tap. Q: What size drill bit should I use before tapping a thread? The tap drill size equals the thread's nominal diameter minus one pitch. For an M8 × 1.25 tap, the drill is 8 − 1.25 = 6.75mm (typically rounded to 6.8mm). Drill too small and the tap breaks; drill too large and the thread has insufficient engagement depth. Tap drill charts — available on the AIMS threading guide — list correct drill sizes for all metric and UNF/UNC thread sizes. Always use the correct drill and cutting fluid for the material being tapped. Q: What is a spiral point versus spiral flute tap? A spiral point tap (also called a gun tap) has a straight flute with an angled cutting face that pushes chips ahead of the tap down into through-holes. It is fast and effective in through-hole tapping, especially in ductile metals. A spiral flute tap has helical flutes that draw chips back up out of the hole — essential for blind holes where chips cannot be pushed through. Using a spiral point tap in a blind hole packs chips at the bottom and risks tap breakage. Q: Can taps and dies be used on stainless steel? Yes, but stainless steel is substantially harder to tap than mild steel and work-hardens quickly. Use a high-speed steel (HSS) or cobalt tap rather than a carbon steel tap. Apply cutting fluid generously — a sulphur-based cutting oil or dedicated tapping compound performs significantly better than general-purpose oils on stainless. Turn the tap forward half a turn, then back a quarter turn to break chips and prevent work-hardening. Use a slower, steadier speed with hand tapping. Q: How do I use a die to cut an external thread? Secure the workpiece vertically in a vice. Apply cutting fluid to the stock. Place the die in the die stock with the chamfered (lead-in) side facing down toward the work. Start by pressing down while rotating slowly — the lead chamfer guides the die squarely onto the stock. Turn forward half a turn, then back a quarter turn to break chips. Keep applying fluid throughout. Check alignment frequently with a square. If resistance builds suddenly, back off and clear chips before continuing. Browse adjustable hand reamers at AIMS Industrial for application support and stock confirmation.
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Spanner Size Chart: Metric & Imperial Wrench Sizes
Use this spanner size chart to find the right spanner for the fastener or fitting in front of you — whether metric, imperial (AF), or BSP. Spanner size refers to the across-flats (AF) measurement of the fastener head, which is the same dimension the spanner jaw must match. Getting it right avoids rounded heads and stripped fittings. This guide is part of AIMS Industrial's curated Engineering Reference Charts library — 78 reference articles across fasteners, threading, bearings, lubrication and safety standards. Spanner Size Selector — Match Spanner to Bolt This chart is a working spanner selector — every size row links to the AIMS spanner range or a covering set. Use the scenarios below to find the right AF spanner fast, or scroll to the chart tables below. How to use: 1. Identify bolt size or AF spanner size needed 2. Click the size in the chart for the matching range 3. Open the right AIMS spanner set M4–M8 Light Workshop 7–13mm AF — small fasteners 7–13mm View → M10–M16 General 17–24mm AF — workshop default 17–24mm View → M18–M24 Heavy Bolts 27–36mm AF — structural / engine 27–36mm View → Imperial AF (SAE) Inch sizes — older / US specs AF View → BSP Fittings Hydraulic & pneumatic fittings BSP View → Ratcheting Spanners Speed in restricted spaces Ratchet View → Adjustable Spanner One-tool catch-all (shifter) Shifter View → Browse Stahlwille / Ko-Ken / Bahco Premium European + Asian range Brands View → Quick rule: spanner size is the AF (across-the-flats) measurement — the bolt head's outside dimension, not the bolt thread. M10 bolt = 17mm AF spanner. M12 = 19mm AF. AIMS stocks Stahlwille, Ko-Ken, Bahco and Trax spanner sets covering 6–32mm metric and 1/4"–1-1/4" imperial. Need help? Call (02) 9773 0122. Jump to: How Sizes Work Bolt → Spanner Metric Range Imperial AF Conversion BSP Fittings Open / Ring / Combo Related Selectors How Spanner Sizes Work Spanner size is measured across the flats (AF) of the fastener head — the distance between two parallel faces of the hex. A 19mm spanner fits any fastener that measures 19mm across the flats, regardless of whether the fastener thread is metric or imperial. Bolt thread diameter (M8, M12 etc.) and spanner size are different measurements. The tables below show the relationship between bolt size and spanner size. An M8 bolt has a 13mm hex head — so you need a 13mm spanner, not an 8mm one. Open-end spanners engage two flats and are faster to use. Ring spanners (12-point) engage all six flats and are preferred for high-torque work, as they're less likely to round a fastener head. Combination spanners give you both in one tool — open end for speed, ring end for torque. Metric Spanner Size Chart — Bolt Thread to Spanner Size This table shows the spanner size required for each metric bolt thread size. Sizes follow ISO standard hex dimensions. Always confirm against the actual fastener if in doubt — some manufacturers use non-standard hex sizes. Bolt Size Spanner Size (AF) Common Application M4 7mm Small fasteners, electronics, thin sheet M5 8mm Small fasteners, covers, guards M6 10mm Most common — engines, brackets, interior panels M7 11mm Less common metric size M8 13mm General engineering, structural fasteners M10 17mm General engineering, machinery M12 19mm Automotive, structural, machinery M14 22mm Suspension components, driveline M16 24mm Heavy structural fasteners M18 27mm Heavy fasteners, industrial equipment M20 30mm Large structural and machinery fasteners M22 32mm Heavy machinery, plant equipment M24 36mm Large bolts, plant and structural M27 41mm Heavy plant and infrastructure M30 46mm Large plant, civil infrastructure M33 50mm Very large structural fasteners M36 55mm Heavy infrastructure, mining Metric Spanner Size Chart — Full Range The table below covers the full common metric spanner range from 6mm to 50mm, showing typical fastener applications for each size. Useful when you know which spanner you have and need to identify what it fits. Spanner Size (mm) Typical Bolt / Fastener Notes 6 M3.5 bolt head Uncommon — small precision fasteners 7 M4 bolt head Electronics, small assemblies 8 M5 bolt head Light fasteners, covers 9 General use Less common in metric sets 10 M6 bolt head Most common metric spanner size 11 M7 bolt head Less common metric size 12 General use Some fittings and M7 fine thread 13 M8 bolt head Common workshop size 14 1/8" BSP fittings Hydraulic and pneumatic fittings 15 General use Some M9 fasteners, brake fittings 16 General use Some M10 fine thread 17 M10 bolt head (standard) Common automotive and machinery size 18 General use Some hydraulic fittings 19 M12 bolt head Also close to 3/4" AF (19.05mm) 21 General use Some wheel nuts and couplings 22 M14 bolt head / 3/8" BSP Common fitting and fastener size 24 M16 bolt head Heavy structural applications 26 1/2" BSP fittings Most common BSP fitting size 27 M18 bolt head Industrial and heavy equipment 30 M20 bolt head Large structural fasteners 32 M22 bolt head / 3/4" BSP Heavy machinery and plant 36 M24 bolt head Large bolts, plant equipment 41 M27 bolt head / 1" BSP Heavy plant and large fittings 46 M30 bolt head Large plant and infrastructure 50 M33 bolt head / 1-1/4" BSP Very large structural and fittings Imperial (AF) Spanner Size Chart Imperial spanners are sized in fractions of an inch and are common on American-manufactured vehicles and equipment, agricultural machinery, and older plant. The sizing follows the across-flats (AF) convention — the same measurement system as metric, just in inches. Spanner Size (inch) Decimal (inch) Metric Equivalent (mm) Typical Use 1/4" 0.250" 6.35 Very small fasteners 5/16" 0.313" 7.94 Small fasteners 3/8" 0.375" 9.53 Light fasteners 7/16" 0.438" 11.11 General use 1/2" 0.500" 12.70 General use 9/16" 0.563" 14.29 General use 5/8" 0.625" 15.88 General use 11/16" 0.688" 17.46 General use 3/4" 0.750" 19.05 Common — close to 19mm metric 13/16" 0.813" 20.64 General use 7/8" 0.875" 22.23 Common — close to 22mm metric 15/16" 0.938" 23.81 General use 1" 1.000" 25.40 General use 1-1/16" 1.063" 26.99 Close to 27mm metric 1-1/8" 1.125" 28.58 General use 1-3/16" 1.188" 30.16 Close to 30mm metric 1-1/4" 1.250" 31.75 General use 1-5/16" 1.313" 33.34 General use 1-3/8" 1.375" 34.93 General use 1-7/16" 1.438" 36.51 Close to 36mm metric 1-1/2" 1.500" 38.10 General use Metric to Imperial Spanner Conversion Chart No exact metric-to-imperial match exists for most sizes — the measurement systems are independent. The table below shows the closest imperial spanner to each common metric size. Where the difference is large, the fit will be too loose for torqued fasteners. Always use the correct size where precision matters. Metric Size (mm) Closest Imperial Imperial in mm Difference 7 9/32" 7.14 +0.14mm 8 5/16" 7.94 -0.06mm (tight) 10 3/8" 9.53 -0.47mm (won't fit) 11 7/16" 11.11 +0.11mm 13 1/2" 12.70 -0.30mm (won't fit) 14 9/16" 14.29 +0.29mm 17 11/16" 17.46 +0.46mm 19 3/4" 19.05 +0.05mm ✓ 22 7/8" 22.23 +0.23mm 24 15/16" 23.81 -0.19mm (tight) 27 1-1/16" 26.99 -0.01mm ✓ 30 1-3/16" 30.16 +0.16mm 32 1-1/4" 31.75 -0.25mm (tight) 36 1-7/16" 36.51 +0.51mm 41 1-5/8" 41.28 +0.28mm 46 1-13/16" 46.04 +0.04mm ✓ BSP Fitting Spanner Sizes BSP (British Standard Pipe) sizes are nominal pipe bore sizes — not the actual across-flats measurement of the fitting. This catches people out: a 1/2" BSP fitting requires a 26mm spanner, not a 1/2" (12.7mm) one. The table below shows the spanner size needed for common BSP male threaded fittings. Sizes may vary slightly between fitting types and manufacturers. BSP Size Spanner Size (AF) Common Application 1/8" BSP 14mm Small fittings, gauges, bleed nipples 1/4" BSP 19mm Air fittings, small hydraulic connectors 3/8" BSP 22mm General plumbing, pneumatic lines 1/2" BSP 26mm Most common BSP size — hydraulic and pneumatic fittings 3/4" BSP 32mm General industrial plumbing 1" BSP 41mm Larger hydraulic and plumbing fittings 1-1/4" BSP 50mm Large pipe and industrial fittings 1-1/2" BSP 55mm Large pipe fittings 2" BSP 65mm Very large industrial fittings Open-End, Ring and Combination Spanners Choosing the right type of spanner matters as much as choosing the right size. Each type suits different situations. Spanner Type How It Grips Use When Limitation Open-end 2 flats Access is tight, fastener is in good condition, speed matters More likely to round worn fasteners Ring (box-end) All 6 flats (12-point) High torque, corroded or tight fasteners, precision work Must be dropped over the fastener — needs clearance above Combination Open one end, ring other end General use — ring to break loose or torque, open to run down Both ends are the same size Flare nut (crow's foot) 5 flats — slotted ring Brake and fuel lines — allows the spanner to pass over the line Lower torque rating than a solid ring spanner Ratchet spanner Ring with ratchet mechanism Tight spaces where a full swing arc isn't possible Not suited to very high torque Related AIMS Selectors This selector pairs with AIMS's other fastener & tool guides: Socket Size Chart Selector — when you need socket + ratchet not open-end spanner. Types of Spanners — open-end / ring / combo / flare / podger reference. Ratchet Spanner Guide — flex-head vs reversible vs gear count. Adjustable Spanner Guide — shifter selection and use. Choosing Socket Drive Size — when to step up or down a drive size. Metric Bolt Size Guide — bolt thread to head size reference. Metric Bolt Torque Chart — torque values per grade and size. BSP vs NPT vs UNC Thread Standards — fitting thread identification. Or browse the full spanners & wrenches range, ring spanners, ratcheting spanners, or by brand: Stahlwille, Ko-Ken, Bahco, Trax. Next-day Australia-wide dispatch from our Milperra warehouse.Frequently Asked Questions What is the most common spanner size?In metric, 10mm is the most frequently used spanner size — it fits M6 bolt heads, which appear on engines, brackets, and interior components across virtually every vehicle and machine. In imperial, 3/4" and 7/8" are among the most common SAE sizes. What size spanner fits an M8 bolt?An M8 bolt has a 13mm hex head, so you need a 13mm spanner. The bolt diameter (8mm) and the spanner size (13mm) are different measurements — the spanner fits the hex head, not the thread shank. This is a common source of confusion. What's the difference between AF and metric spanners?Both metric and AF (across flats) spanners measure the jaw opening in the same way — across the flats of the fastener. The difference is the unit: metric spanners are sized in millimetres, AF spanners in fractions of an inch. An AF spanner will be labelled in fractions (3/4", 7/8" etc.), while a metric spanner will be labelled in whole millimetres (19mm, 22mm etc.). Can I use a metric spanner on an imperial fastener?In some cases yes — where the metric size is very close to the imperial size. The best match is 19mm and 3/4" (19.05mm), where the difference is only 0.05mm. However, for torqued fasteners always use the correct spanner to avoid rounding. The conversion chart above shows the closest matches and their differences. What spanner do I need for BSP fittings?BSP fittings require a larger spanner than the pipe size suggests. The most common size — 1/2" BSP — requires a 26mm spanner, not a 1/2" (12.7mm) one. Always refer to the BSP fitting spanner chart above, as the pipe bore size and the fitting hex size are completely different measurements. What does AF mean on a spanner?AF stands for Across Flats — the distance between two parallel faces of a hex fastener. Both metric and imperial spanners are sized by this measurement. When you see a spanner marked "3/4" AF, it means the jaw opens to 3/4 of an inch across the flats. Metric spanners don't usually carry the AF label but are sized the same way. What's the difference between a ring spanner and an open-end spanner?A ring spanner has a closed circular end that fits over the fastener and engages all six flats. This reduces the risk of rounding and allows more torque to be applied safely. An open-end spanner has a U-shaped jaw that engages only two flats — it can be inserted sideways, which is useful in tight spaces, but it's more likely to slip or round a worn fastener. For any high-torque application, use the ring end. What is a flare nut spanner used for?A flare nut spanner (also called a crow's foot spanner) has a ring end with a slot cut into it, allowing it to pass over a brake line or fuel line before engaging the fitting nut. It grips five of the six flats rather than two, giving better purchase than an open-end spanner while still allowing it to be slid onto a fitting with a line attached. They are essential for brake and fuel line work where a standard ring spanner cannot be dropped over the top. Got the size? Get the spanner. Shop our full range of metric & imperial spanners From open-end to ring and combination spanners — AIMS Industrial stocks sizes across metric, AF, and BSP standards, ready to ship Australia-wide. Browse spanners Talk to a specialist People Also Ask — Spanner Size Chart: Metric & Imperial Wrench Sizes Q: What spanner size fits an M10 bolt? An M10 coarse bolt (1.5 mm pitch) uses a 17 mm spanner across the flats. M10 fine (1.25 mm pitch) also uses 17 mm. This is one of the most common sizes in Australian trade and maintenance work — a 17 mm open-end or combination spanner is considered a toolbox essential. Q: How do I convert spanner sizes from metric to imperial? Divide the metric jaw size in mm by 25.4 to get inches. A 13 mm spanner equals approximately 1/2" (actually 12.7 mm, so there's a slight mismatch — never substitute if the fit is loose). Common near-equivalents: 11 mm ≈ 7/16", 13 mm ≈ 1/2", 17 mm ≈ 11/16", 19 mm ≈ 3/4". Q: What size spanner is needed for BSP fittings? BSP (British Standard Pipe) fitting sizes are not the same as their thread diameter — a 1/2" BSP fitting uses a 27 mm spanner across the hex, while a 3/4" BSP uses 32 mm. Always check the fitting's hex size, not its pipe thread designation, to choose the right spanner. Q: What is the difference between an open-end and combination spanner? An open-end spanner engages two faces of the fastener and suits confined spaces where a ring won't fit. A combination spanner has an open end on one side and a ring (box) end on the other — the ring end gives better grip and is less likely to round off a fastener, making it the better choice when access allows. See AIMS's full adjustable hand reamers range — trade pricing and Australia-wide despatch. For open end wrenches, see our open end wrenches range stocked across Australia.
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Socket Size Chart: Metric, Imperial & Drive Sizes
Socket size is the across-flats (AF) measurement of a fastener head, sized in millimetres (metric) or fractions of an inch (imperial/SAE). A 19mm socket equals 3/4" (19.05mm). The quick-reference table below lists the most-used sizes in both systems; full metric, imperial and drive-size charts are further down. Quick answer — socket conversions Metric → Imperial: 8mm ≈ 5/16" · 10mm ≈ 3/8" · 11mm ≈ 7/16" · 13mm ≈ 1/2" · 14mm ≈ 9/16" · 15mm ≈ 19/32" · 16mm ≈ 5/8" · 17mm ≈ 11/16" · 19mm ≈ 3/4" · 21mm ≈ 13/16" · 22mm ≈ 7/8" · 24mm ≈ 15/16" · 27mm ≈ 1-1/16" · 30mm ≈ 1-3/16" Imperial → Metric: 1/4" ≈ 6.5mm · 5/16" ≈ 8mm · 3/8" ≈ 10mm · 7/16" ≈ 11mm · 1/2" ≈ 13mm · 9/16" ≈ 14mm · 5/8" ≈ 16mm · 3/4" ≈ 19mm · 7/8" ≈ 22mm · 15/16" ≈ 24mm ⚠️ Close ≠ exact. For torqued fasteners always use the correct system to avoid rounding the head. For more engineering reference charts and selection tables, see our Engineering Reference Charts hub — covering fasteners, bearings, lubrication, measuring, welding and Australian standards. Socket Size Selector — Find the Right Socket for the Job This chart is a working socket selector — every chart row links to a stocked AIMS product (Ko-Ken, Stahlwille or Trax) or to the matching range. Use the scenarios below to land on the right drive size + socket size fast, or scroll to the chart tables below. How to use: 1. Match drive size to job type 2. Find the metric or imperial socket size in the chart 3. Click the size to view the stocked product Electronics & Small Screws 1/4" drive — fine work 1/4" View → General Workshop 3/8" drive — most-common 3/8" View → Automotive & Engineering 1/2" drive — bolts to M22 1/2" View → Heavy Truck & Mining 3/4" drive — high-torque 3/4" View → Impact / Air Tools Impact-rated black sockets Impact View → Torx & Hex Drive Bolts Torx & hex bit sockets Torx/Hex View → Browse Socket Sets Multi-piece complete sets Sets View → Ko-Ken / Stahlwille / Trax Top brands stocked Brands View → Quick rule: 1/4" drive for small jobs (electronics, dash trim), 3/8" for general workshop and automotive, 1/2" for chassis and engine bolts (M10-M22), 3/4" for heavy truck and mining (M24+). For impact tools, use black impact-rated sockets only — chrome sockets shatter under hammer load. Need help? Call (02) 9773 0122. Jump to: How Sockets Work Metric 1/4" Metric 3/8" Metric 1/2" Imperial SAE Conversion Deep vs Standard Choosing Drive Size Related Selectors Socket Size Chart — Metric to Imperial Quick Reference The most common metric socket sizes and their closest imperial (SAE) equivalents: Metric Imperial (SAE) Metric Imperial (SAE) 8mm 5/16" 17mm 11/16" 10mm 3/8" 19mm 3/4" 11mm 7/16" 22mm 7/8" 13mm 1/2" 24mm 15/16" 14mm 9/16" 27mm 1-1/16" How Socket Sizes Work Socket sizes refer to the across-flats measurement of the fastener head — the same dimension used for spanners and open-end wrenches. A 19mm socket fits a fastener with 19mm across the flats, regardless of whether the fastener itself is metric or has a metric thread. Drive size is separate from socket size. It refers to the square drive on the ratchet or extension bar that connects to the socket — 1/4", 3/8" or 1/2". A 3/8" drive 13mm socket and a 1/2" drive 13mm socket both fit the same nut, but the larger drive handles more torque. Standard (shallow) sockets work for most fasteners. Deep sockets are needed where the fastener shank protrudes through the nut — common on wheel studs, bolts with long thread engagement, and spark plugs. Metric Socket Size Chart — 1/4" Drive A 1/4" drive is suited to light work: electronics, small engines, interior trim, and torque-sensitive applications. Typical range is 4mm–15mm. Handles up to approximately 35 Nm. Socket Size (mm) Drive Size Typical Use 4 1/4" Small screws, electronics 5 1/4" Small fasteners 5.5 1/4" Small engine components 6 1/4" General light fasteners 7 1/4" General light fasteners 8 1/4" Interior panels, brackets 9 1/4" General use 10 1/4" Most common metric bolt head 11 1/4" General use 12 1/4" General use 13 1/4" M8 bolt head 14 1/4" General use 15 1/4" Upper limit of 1/4" drive Metric Socket Size Chart — 3/8" Drive A 3/8" drive covers the widest general-purpose range — from 8mm up to 24mm in most sets. The right choice for most automotive, machinery, and workshop tasks. Handles up to approximately 100–135 Nm. Socket Size (mm) Drive Size Common Fastener 8 3/8" M5 bolt head 9 3/8" General use 10 3/8" M6 bolt head — most common 11 3/8" General use 12 3/8" M8 bolt head (some) 13 3/8" M8 bolt head (standard) 14 3/8" M9 bolt head 15 3/8" General use 16 3/8" M10 bolt head (some) 17 3/8" M10 bolt head (standard) 18 3/8" M11 bolt head 19 3/8" M12 bolt head / wheel nuts (many) 21 3/8" General use 22 3/8" M14 bolt head 24 3/8" M16 bolt head Metric Socket Size Chart — 1/2" Drive A 1/2" drive is for heavy work: wheel nuts, suspension components, heavy machinery, and high-torque fasteners. Standard range is 17mm–50mm. Handles 200 Nm and above depending on the tool. Socket Size (mm) Drive Size Common Fastener 17 1/2" M10 bolt head 19 1/2" M12 bolt head / most wheel nuts 21 1/2" General heavy use 22 1/2" M14 bolt head 24 1/2" M16 bolt head 27 1/2" M18 bolt head 30 1/2" M20 bolt head 32 1/2" M22 bolt head 33 1/2" Wheel nuts (heavy vehicles) 36 1/2" M24 bolt head 38 1/2" Heavy machinery 41 1/2" Heavy machinery / axle nuts 46 1/2" Axle nuts / heavy plant 50 1/2" Large axle and hub nuts Imperial (SAE) Socket Size Chart Imperial sockets are sized in fractions of an inch and are common on American-manufactured vehicles and equipment, agricultural machinery, and older plant. The sizing convention follows SAE (Society of Automotive Engineers) standards. Available in 1/4", 3/8" and 1/2" drive. Socket Size (inch) Decimal (inch) Metric Equivalent (mm) Typical Drive 3/16" 0.188" 4.8 1/4" 1/4" 0.250" 6.35 1/4" 5/16" 0.313" 7.9 1/4" 3/8" 0.375" 9.5 1/4" / 3/8" 7/16" 0.438" 11.1 3/8" 1/2" 0.500" 12.7 3/8" 9/16" 0.563" 14.3 3/8" 5/8" 0.625" 15.9 3/8" 11/16" 0.688" 17.5 3/8" 3/4" 0.750" 19.1 3/8" / 1/2" 13/16" 0.813" 20.6 3/8" / 1/2" 7/8" 0.875" 22.2 1/2" 15/16" 0.938" 23.8 1/2" 1" 1.000" 25.4 1/2" 1-1/16" 1.063" 27.0 1/2" 1-1/8" 1.125" 28.6 1/2" 1-3/16" 1.188" 30.2 1/2" 1-1/4" 1.250" 31.8 1/2" 1-5/16" 1.313" 33.3 1/2" 1-3/8" 1.375" 34.9 1/2" 1-1/2" 1.500" 38.1 1/2" Metric to Imperial Socket Conversion Chart No exact metric-to-imperial match exists — socket sizes are based on different measurement systems. The table below shows the closest imperial socket to each common metric size. In most cases the fit will be too loose for torquing; use the correct metric socket where precision matters. Metric Size (mm) Closest Imperial Difference 8 5/16" +0.1mm 9 3/8" +0.5mm 10 3/8" -0.5mm 11 7/16" +0.1mm 12 15/32" -0.1mm 13 1/2" -0.3mm 14 9/16" +0.3mm 15 19/32" +0.0mm 16 5/8" -0.1mm 17 11/16" +0.5mm 18 11/16" -0.5mm 19 3/4" +0.1mm 21 13/16" -0.6mm 22 7/8" +0.2mm 24 15/16" -0.2mm 27 1-1/16" +0.0mm 30 1-3/16" +0.2mm 32 1-1/4" -0.2mm Standard vs Deep Socket Guide Standard (shallow) sockets handle the vast majority of work. Deep sockets are needed when the bolt shank extends through the nut, leaving the socket unable to seat properly on a shallow socket. Common applications for deep sockets include wheel studs, exhaust bolts, spark plugs, and any application where thread is exposed above the nut. Socket Type Depth Use When Standard (shallow) ~25–35mm Bolt head or nut flush / minimal thread protrusion Deep ~60–75mm Thread protrudes through nut (wheel studs, spark plugs) Extra deep / pass-through 100mm+ Long studs, threaded rod, specialised applications Choosing the Right Drive Size Drive size determines torque capacity and tool compatibility. Match the drive to the job — using a 1/2" drive on small fasteners risks overtorquing and rounding; using a 1/4" drive on large fasteners risks snapping the drive or the socket. Drive Size Socket Range Torque Range Typical Applications 1/4" 4–15mm / 3/16"–9/16" Up to ~35 Nm Electronics, small engines, interior trim, torque-sensitive work 3/8" 8–24mm / 5/16"–15/16" 35–135 Nm General automotive, machinery, most workshop tasks 1/2" 17–50mm+ / 11/16"–2" 135 Nm+ Wheel nuts, suspension, heavy machinery, high-torque fasteners 3/4" 33–75mm+ 700 Nm+ Heavy plant, earthmoving, structural work 1" 50mm+ 2,000 Nm+ Mining, large infrastructure, industrial plant Related AIMS Selectors This selector pairs with AIMS's other fastener & tool guides: Spanner Size Chart — metric AF spanner sizes mapped to bolt size + spanner products. Choosing Socket Drive Size — detailed walkthrough on when to step up or down a drive size. Ratchet Spanner Guide — flex-head vs reversible vs gear count selection. Adjustable Spanner Guide — shifter selection and use. Types of Spanners — open-end / ring / combo / flare / podger reference. Impact Driver vs Impact Wrench — when to use impact sockets vs hand tools. Socket Head Cap Screw Guide — Allen/hex socket fastener reference (paired with socket bits). Metric Bolt Torque Chart — torque values per grade and size (use with torque wrench). Or browse the full sockets range, ratchets & sockets, spanners & wrenches, or by brand: Ko-Ken, Stahlwille, Trax. Next-day Australia-wide dispatch from our Milperra warehouse.Frequently Asked Questions What is 10mm socket in imperial? A 10mm socket is approximately 3/8 inch (9.525mm). The match is close — 10mm is 0.475mm larger — but for torqued fasteners always use the 10mm socket on metric bolts. 10mm fits M6 bolt heads which are extremely common on engines and brackets. Is 3/8 inch socket the same as 10mm? No, they are close but not identical. A 3/8 inch socket measures 9.525mm and a 10mm socket measures 10mm — a 0.475mm difference. A 3/8" socket will fit loosely on a 10mm hex and risks rounding the head under torque. Use the correct system for the fastener. What is 13mm socket in imperial? A 13mm socket is approximately 1/2 inch (12.7mm). The difference is only 0.3mm. 13mm is the standard size for M8 hex bolts — one of the most-used sizes in automotive and machinery work. What is 14mm socket in imperial? A 14mm socket is approximately 9/16 inch (14.29mm). 14mm is commonly used for M10 hex bolts, brake calipers and many engine fasteners. What is 15mm socket in imperial? A 15mm socket is approximately 19/32 inch (15.08mm). 15mm is less common in the standard imperial range — most SAE sets skip from 9/16" (14.29mm) to 5/8" (15.88mm). What is 16mm socket in imperial? A 16mm socket is approximately 5/8 inch (15.88mm). 5/8" is 0.125mm smaller than 16mm — usable on a light fit but always use 16mm for torqued M10 fine-thread fasteners. What is 17mm socket in imperial? A 17mm socket is approximately 11/16 inch (17.46mm). 17mm is one of the most common sizes used on M10 hex bolt heads and brake hardware. What is 19mm socket in imperial? A 19mm socket is equivalent to 3/4 inch (19.05mm) — only 0.05mm difference. This is one of the closest metric/imperial pairs and either socket can usually be used interchangeably on a light fit. What is 21mm socket in imperial? A 21mm socket is approximately 13/16 inch (20.64mm). 21mm is the standard size for many wheel lug nuts on European vehicles. What is 22mm socket in standard? A 22mm socket is approximately 7/8 inch (22.23mm). 22mm is widely used on M14 hex bolts and is a common spark plug socket size. What is 28mm socket in imperial? A 28mm socket is approximately 1-1/8 inch (28.58mm). The difference is 0.58mm — use the correct metric size for axle nuts and large machinery fasteners. What are socket sizes in order? Common metric socket sizes in order: 4, 4.5, 5, 5.5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 27, 30, 32, 36mm. Common imperial (SAE) sizes in order: 5/32, 3/16, 7/32, 1/4, 9/32, 5/16, 11/32, 3/8, 7/16, 1/2, 9/16, 5/8, 11/16, 3/4, 13/16, 7/8, 15/16, 1, 1-1/16, 1-1/8 inch. What is the most common socket size? In metric, 10mm is the most frequently used socket size — it fits M6 bolt heads which appear on engines, brackets and interior components across virtually every vehicle and machine. In imperial, 3/8" and 7/16" are among the most common SAE sizes. Can I use a metric socket on an imperial fastener? In some cases yes — where the metric size is very close to the imperial size. For example, an 11mm socket is almost identical to a 7/16" (11.1mm). However, for torqued fasteners, always use the matching socket to avoid rounding. The closest metric-to-imperial matches are shown in the conversion chart above. When do I need a deep socket? Use a deep socket when the bolt shank protrudes through the nut, preventing a standard socket from seating properly. Common applications include wheel studs (where the thread extends past the wheel nut), spark plugs, and long threaded rod assemblies. If a standard socket rocks or won't engage the full depth of the hex, switch to a deep socket. What is the difference between 6-point and 12-point sockets? A 6-point socket has six internal contact points and grips the flat sides of the hex fastener. It is less likely to round worn or corroded fasteners and is the preferred choice for high-torque work. A 12-point socket has twelve contact points, allowing it to engage the fastener at more angles — useful in tight spaces where swing is limited. For general use, 6-point is the better choice. Ready to get to work? Shop our full range of sockets & socket sets From 1/4" drive metric to 1/2" drive imperial — AIMS Industrial stocks sockets for every drive size and standard, ready to ship Australia-wide. Browse sockets Talk to a specialist People Also Ask — Socket Size Chart: Metric, Imperial & Drive Sizes 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 15 mm socket is nearly identical to 19/32". 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 does 6-point vs 12-point socket mean? 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.
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Clamping Made Easier and Faster with Lockjaw
(Taken from this post by Sutton Tools. Republished with permission. Edited for point of view, recency and relevance.) Over many years, Lockjaw pliers and clamps have gained a devoted following of tradespeople, weekend warriors and hobbyists. Quite simply, they are known to be much easier and more reliable to use than other brands. The key is the ability for users to set a pressure – from slight to extreme – via the unique Set and Forget™ adjustor. The plier or clamp will then hold this same pressure automatically, self-adjusting to grip the correct distance according to the thickness of the material. This feature is extremely useful when clamping different materials. For example, pine wood could be damaged at the pressure you’d use to hold a slab of Masonite, and Masonite could drop from the clamp at the pressure you’d use for a softwood. So, you want to set the pressure to suit the material, regardless of its thickness. Most importantly, the process of setting the pressure is by turning a screw mechanism embedded in the tool’s handle; so it’s a single-handed operation. This capability is critical for clamping, because you typically need the other hand to manipulate the material you are holding. Hence, the Lockjaw promise: 7x faster, 100% easier. In manufacturing, construction and similar industries involving regular clamping of materials, this time-saving ability can translate to thousands of dollars a year in process time savings. More stocks now available As a tool manufacturer and supplier, Sutton Tools is proud to be the official Australian distributor of Lockjaw products and has a reputation for maintaining ready-to-ship stocks of over 16,000 SKUs at adequate levels for their customers’ needs. However, due to the popularity of Lockjaw pliers and clamps, they have not always been able to prevent shortages and backorders. To address this, they have recently reorganised and streamlined their Lockjaw supply chain processes, which means stock availability should no longer be an issue. They’ve also improved the packaging, so it’s less likely to suffer damage in transit. Shop for Lockjaw pliers and clamps now. 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. People Also Ask — Locking Pliers & Clamps Q: What are locking pliers used for? Locking pliers — sometimes called by the trade as a self-grip or mole-type tool — clamp onto a workpiece and stay locked with strong, hands-free pressure until released. That makes them a cross between pliers and a clamp. Tradespeople use them to grip and turn rounded or damaged fasteners, hold parts together for welding or drilling, act as a temporary handle or clamp, and free seized nuts and bolts. Because the jaws lock under adjustable pressure, you can set them onto an item and let go, freeing both hands for other work. Their versatility is why they are a staple in automotive, fabrication and general maintenance kits. Q: How do you adjust and lock the pliers onto a workpiece? Locking pliers have an adjusting screw in the end of one handle that sets the jaw opening and clamping force. You turn the screw so the jaws are slightly smaller than the item, then squeeze the handles until they snap shut and lock with firm pressure. If they are too loose or too tight, you release and fine-tune the screw and try again. A release lever in the handle pops them open when you are done. The knack is setting the screw so the lock engages with a positive snap and real clamping force — too loose and they slip, too tight and they will not close. Q: What is the difference between locking pliers and a clamp? A standard clamp is purpose-built to hold work together with a fixed frame and a screw or lever, giving steady, distributed pressure for tasks like glue-ups and welding fit-up. Locking pliers are a portable, hand-sized tool that locks onto a point with concentrated jaw pressure, doubling as a gripping and turning tool as well as a temporary clamp. Locking clamps blend the two — locking-plier mechanisms fitted with clamp-style jaws (such as C-clamp or sheet-metal jaws) for holding fabrication work. Choose a clamp for steady holding over a wider area, and locking pliers where you need a quick, strong, portable grip or a turning tool. Q: What jaw shapes are available on locking pliers? Locking pliers come with several jaw styles for different jobs. Curved jaws are the general-purpose shape and grip round and hex items well. Straight or long-nose jaws reach into tight spots and grip small parts. Wide or sheet-metal jaws spread the clamping force to hold panels flat without marking, which suits fabrication. C-clamp jaws turn the tool into a deep-reach welding clamp. Chain and specialty versions grip large or awkward shapes. Matching the jaw shape to the task — gripping, turning, or clamping flat work — gets the best hold, so many workshops keep a few jaw styles on hand. Q: Can locking pliers damage the workpiece? They can, because they grip with concentrated, serrated jaw pressure that can mar soft surfaces, crush thin material or chew up the corners of a fastener if over-tightened. That is a fair trade-off when freeing a seized or already-damaged bolt, but on finished or soft parts it is worth protecting the surface — backing the jaws with cloth or soft pads, using smooth or wide jaws, or choosing a proper clamp instead. Set the clamping screw only as tight as the job needs rather than maximum. Used with that bit of judgement, locking pliers grip securely without leaving unnecessary damage. Need adjustable hand reamers? Browse the AIMS range at adjustable hand reamers.
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