A centre punch is a hardened steel marking-out tool used to create a small indentation in metal — the locating dimple that stops a drill bit wandering off the mark. Used together with a scriber (for drawing layout lines) and often a prick punch (for sub-millimetre layout accuracy), centre punches are the workshop standard for precision marking-out before drilling, fitting, or assembly. The right tool depends on three decisions: punch type (centre / prick / pin / drift / automatic / transfer), point angle (60° prick for layout, 90° centre punch for drill bit start), and whether you need the spring-loaded automatic mechanism or the hammer-strike manual version. This guide covers all three, the two-stage marking-out technique that every machinist learns, the AU and international brand picture, plus the Sutton + P&N + Stahlwille range stocked at AIMS.
AIMS Industrial stocks the full punches and punch sets range — 35+ active SKUs across Sutton Tools (AU industrial dominant), P&N (AU scribers and automatic punches), Trax (workshop value), and Stahlwille (German premium). Contact the AIMS team or call (02) 9773 0122 for technical advice or bulk supply.
What is a centre punch?
A centre punch is a hand tool consisting of a hardened steel shaft with a tapered conical point at one end and a flat striking face at the other. The point is hardened to approximately Rockwell C 58-62 — harder than mild steel but softer than file teeth — so it can create an indentation in mild and most workshop steels without deforming or chipping. Manual centre punches are struck with a hammer; automatic centre punches use a spring-loaded internal mechanism that fires when downward pressure exceeds the spring threshold.
The marking-out tool family used together in workshop practice:
- Scriber — a hardened steel or tungsten carbide-tipped tool used to draw layout lines on metal surfaces.
- Prick punch — sharp 30°-60° point for precise layout marks at line intersections.
- Centre punch — 90° point used after the prick punch to create the drill bit start indentation.
- Pin punch — parallel-shank punch used to drive pins through holes during assembly/disassembly.
- Drift punch — longer pin punch with a tapered front section for starting pins in deep blind holes.
- Transfer punch — set of precision-ground punches used to mark mating-hole positions from one workpiece onto another.
Centre punch vs prick punch — 90° vs 60° and why you need both
The single most important distinction in workshop marking-out: prick punches and centre punches have different point angles and different jobs. Using them in the wrong order — or using only one when both are needed — is the most common cause of drill bits wandering off the mark.
| Tool | Point angle | Job | When to use |
|---|---|---|---|
| Prick punch (or dot punch) | ~30°-60° (sharp) | Precision layout mark at the exact line intersection | First step in marking out. Sharp point lets you place the mark accurately on scribed lines. |
| Centre punch | ~90° | Widens the prick mark into a cone-shaped dimple for the drill bit point to start in | Second step before drilling. Wider dimple guides the drill bit accurately. |
| Centre punch (drill-bit-matched) | 118° or 140° | Matches drill bit geometry exactly — drill bit seats fully into the punch mark | Specialty use — precision machine shop work where drill wander must be eliminated. |
Why the two-angle system works: a 90° centre punch placed directly on a scribed line will slide off the line edge, producing an inaccurate mark. A sharp 60° prick punch sits precisely in the line intersection. Once the prick mark is verified, the centre punch follows to widen the dimple — the punch tip locates in the prick mark and can't wander.
This is documented across every traditional workshop training reference and every machinist forum (Practical Machinist, Hobby-Machinist, Home Shop Machinist BBS): always use both punches in sequence for any drilling job where accuracy matters.
The two-stage marking-out technique — and why you should file off the deformation
The full workshop marking-out sequence for accurate drilling:
- Apply layout fluid (engineer's blue / Dykem) to the workpiece face. Wait for it to dry. (Optional but standard for precision work.)
- Scribe layout lines using a sharp scriber, straight edge and rule. Cross lines at the centre of each intended hole position.
- Prick punch the intersection of the scribed lines. Hold the prick punch vertical, light hammer tap or hand pressure. Small precise mark.
- Verify the mark with a magnifier — confirm the prick mark sits exactly at the line intersection. If it's slightly off, lean the prick punch toward the correct position and tap again to walk the mark across.
- Centre punch the prick mark — the centre punch tip seats in the prick dimple and a firmer hammer blow widens the cone to drill-bit start size.
- File off the raised metal around the punch mark — the punch deforms metal upward around the dimple. The raised crater rim makes the drill bit hesitate or wander. A few quick strokes with a smooth file flattens the raised metal.
- Drill on the flattened, dimpled mark — the drill bit point locates in the dimple, can't wander, and starts cleanly.
Forum-validated rule from Practical Machinist threads: filing off the raised metal around the centre punch mark is the single technique most workshop drillers skip — and it's the number-one cause of drill bit wander after centre punching. Two strokes with a file fixes it.
For hammer selection on the punch-strike step, see the Hammer Types Guide — a small ball pein or engineer's hammer (4-8 oz / 113-227 g) is the standard punch hammer. Heavier hammers oversize the dimple; lighter hammers don't seat the cone properly.
Manual centre punch — design, materials, hardness
A manual centre punch is a single piece of hardened steel — typically chrome-vanadium (CrV) for the workshop standard tier, sometimes tool steel with knurled grip for premium models. The shaft is straight or has a slight knurled grip section; the point end is heat-treated to Rc 58-62 hardness; the striking end is left at a softer temper so it deforms slightly under hammer strikes rather than chipping (the controlled "mushrooming" workshop trade-off — you re-grind the strike end occasionally rather than catastrophically failing).
Standard sizes range from 2mm to 6mm point body (the cone tapers from this body diameter), with overall lengths typically 100-150mm. The 2mm and 3mm sizes are for thin sheet and precision layout; 4-6mm sizes are workshop standard for plate and section steel.
AIMS-stocked manual centre punches:
- Sutton M707 Centre Punch CRV — Soft Grip (2-6mm sizes) — the AU industrial workshop standard. Massive 3,656-unit inventory across sizes. Soft-grip handle for hand-held use, chrome-vanadium body. From $5.27 per punch.
- Sutton M7070005 Centre Punch Set 5-piece (2-6mm) — full size range in one set. $29.76 for the complete workshop kit.
- Trax ARX-HDCP5 Centre Punch Set 5-piece — workshop value tier. $31.50.
- Stahlwille SW105-8/6 Pin/Centre Punch Set 6-piece with stand — German premium tier with combined pin and centre punch range. $112.59.
Automatic centre punch — how the spring mechanism works
An automatic centre punch eliminates the hammer. The punch body contains an internal spring-loaded mechanism — typically a heavy mass that's released under spring tension when downward pressure on the punch tip exceeds a threshold. The mass strikes the tip from inside the punch body, delivering a controlled hammer-equivalent blow without needing a separate hammer.
The mechanism allows one-handed operation — you hold the workpiece with one hand and press the punch with the other. The strike force is preset and consistent. Most automatic centre punches have an adjustable tension cap that lets you increase or decrease the strike force.
Why workshop users adopt automatic centre punches:
- One-handed operation — no need to grip both hammer and punch.
- Consistent strike force — every mark is the same depth.
- Faster for repetitive marking (production layout, sheet metal jig work).
- No hammer skip risk — the strike happens inside the body, not at the punch top.
- Compact tool — pocketable, fits in fitter's belt pouch.
The forum-validated reliability picture: automatic centre punches are mechanically more complex than manual punches and the failure modes are real. Forum users on Practical Machinist, Garage Journal, Home Shop Machinist BBS and BangShift document specific issues — old Starrett 18C models with threaded replaceable tips that unscrew under use, springs that lose tension, internal cleaning required after years of grit ingress. The next section covers brand reality.
Automatic centre punch brand reality — Starrett, General, Fowler, Eclipse, Rennsteig, PB Swiss, Moore & Wright
The international automatic centre punch brand picture has clear tiers — and the AU-stocked range covers the workshop value-to-premium spread without the US gold-standard top tier. Honest scope is important here.
| Brand | Tier | Forum reputation | AIMS stocked? |
|---|---|---|---|
| Starrett 18A (USA) | US gold standard — one-piece tip | "Lifetime tool" consensus where it works; reliability mixed in some forum threads but newer 18A design improved on older 18C | Not stocked — source on request |
| Starrett 18C (USA) | Heavy duty automatic | "Too strong, can poke holes through sheet metal" (Garage Journal direct quote — critical sizing warning). Older models with threaded replaceable tips had unscrewing issues; newer one-piece design improved. | Not stocked — source on request |
| General Tools (USA) | US value/standard tier | "Cheaper than Starrett but actually quite usable" — forum consensus is General is the practical purchase for most workshops | Not stocked — source on request |
| Fowler HD (Japan) | Japanese mid-tier | ~$22 AU equivalent — "similar quality to Starrett at a fraction of the cost" per forum reviews | Not stocked — source on request |
| Eclipse (UK) | UK premium | Forum-praised — "very nice" automatic centre punches in multiple sizes | Not stocked — source on request |
| Rennsteig (Germany) | German premium | 250N high-force version available ~$42 AU equivalent — specialty heavy-strike work | Not stocked — source on request |
| PB Swiss / Bauman | Swiss precision premium | Workshop solid centre punches well-regarded for fine layout work | Not stocked — source on request |
| Moore & Wright (UK) | UK heritage | Forum users report 60-year service life on UK-made M&W automatic punches — heritage quality | Not stocked — typically second-hand |
| P&N 267AP1125 (AU) | AU automatic — brass body | Brass body design — 125mm length, $20.90 — workshop standard at retail | ✅ Stocked |
| Trax ARX-ACP | Workshop value | $15.40 — entry tier; gets the job done for occasional use | ✅ Stocked |
| Harbor Freight $3.99 (USA budget) | Avoid — budget | Works briefly, internal mechanism fails — forum-flagged as compromised quality | Not stocked / avoid |
Forum-validated reliability technique: "Non-working" Starrett automatic punches are often restorable. Multiple Home Shop Machinist BBS threads document the same approach — disassemble the punch body, clean accumulated grit and dried lubricant from the internal mechanism, lightly oil moving parts, reassemble. Works in most cases. The mechanism is simple mechanical components, not consumables.
AU practical recommendation: for occasional workshop use, the P&N 267AP1125 Brass Auto Centre Punch ($20.90) or Trax ARX-ACP Automatic Centre Punch ($15.40) cover most workshop needs. For sustained production use or precision layout work, the Starrett 18A or General Tools auto punches are the US gold-standard alternatives — sourceable through AIMS supplier network on request.
Pin punches — driving pins through holes
A pin punch is a hardened steel punch with a parallel cylindrical body — no taper at the tip, unlike centre or prick punches. The point face is flat and slightly chamfered. Pin punches are used to drive roll pins, dowel pins, spring pins, hinge pins, and parallel pins through holes during assembly and disassembly.
Sizing matches pin diameter: a 3mm pin punch drives 3mm pins, etc. Standard sizes 2-6mm cover the workshop common range. Longer punches reach deeper into blind holes; shorter punches give better hammer control for visible work.
Workshop technique:
- Match the punch diameter to the pin diameter exactly (no smaller — the smaller punch slips off or bends the pin; no bigger — the punch won't enter the hole).
- Support the workpiece on a bench block, vice or anvil with a clearance hole for the pin to exit through.
- Strike the punch directly inline with the pin — angled strikes mushroom the pin head.
- For tight pins, apply penetrating oil first and let it soak for 30 minutes. (See the Penetrating Oil Guide.)
- For very tight pins or pins that won't budge with hand strikes, use a punch with a longer reach to allow more powerful hammer blows.
AIMS-stocked pin punches:
- Sutton M706 Pin Punch CRV — Soft Grip — sizes 2-6mm — workshop volume leader (2,992 units inventory).
- Sutton M7060005 Pin Punch Set 5-piece (2-6mm) — $34.62.
- Stahlwille Punch Pin — German precision, sizes 1.4-3.4mm × 82-100mm. $26-$32.
Drift punches and parallel pin punches — longer reach for deep work
A drift punch (sometimes called a "starter punch") has a tapered front section narrowing to the working tip — the taper provides initial strength for breaking a pin loose. A parallel pin punch is fully parallel from end to end and is used after the drift to drive the pin through. The combination drift + pin punch is the workshop technique for stubborn pins.
Long parallel pin punches (typically 150-200mm overall) are useful for driving pins through deep blind holes where a short pin punch can't reach the pin head. Stahlwille's SW108 series in 6-piece sets covers the parallel pin punch range for German-quality workshop use.
- Stahlwille SW108/6 Parallel Pin Punch 6-piece with textile wallet — $139.15.
- Stahlwille SW108/6 Parallel Pin Punch 6-piece with plastic stand — $118.08.
- Stahlwille SW102-5/6 Pin/Chisel Punch 6-piece wallet — combined pin punch + cold chisel set. $182.16.
Engineers scriber — marking lines on metal
An engineers scriber is a hand tool with a hardened-steel or tungsten-carbide-tipped point used to draw layout lines on metal surfaces. The hardened tip cuts a thin line into the metal — more permanent than pencil or marker, visible through metalworking fluids, and locatable by feel as well as sight.
Scriber design varies but the common features are: knurled grip section, hardened tip (often replaceable on premium models), 90° bend point on dual-ended scribers (one straight tip for general layout, one 90° bent tip for marking inside curves and inaccessible areas), and a pocket clip for tradie use.
AIMS-stocked scribers (P&N range):
- P&N 267M06020 Workshop Engineers Scriber 270mm — 90° Bend Point Stainless Steel — dual-ended workshop scriber. $8.91.
- P&N 267M06041 Workshop Scriber Engineers Tungsten Tip 150mm Stainless Steel — tungsten carbide tip for hardened materials. $9.05.
- P&N 267QM0550 Workshop Quick Changeable Magnetic Pick-Up and Hooks Scriber Kit — multi-tip scriber kit with magnet base for retrieving small parts. $22.98.
Tungsten carbide vs hardened steel scriber tips — which is better?
The scriber tip material determines what surfaces the scriber can mark.
| Tip material | Hardness | Marks | Trade-off |
|---|---|---|---|
| Hardened steel (HSS) | Rc 60-65 | Mild steel, aluminium, brass, copper, soft non-ferrous | Cheap; tip wears with use; can't mark hardened steel or stainless reliably |
| Tungsten carbide | Rc 90-94 | Hardened tool steel, stainless steel, ceramics, glass, all softer materials | More expensive; tip brittle (chips if dropped on hard surface); minimal pressure required for clear mark |
| Diamond-tipped | Hardest available | All materials including tungsten carbide tooling and ceramic substrates | Specialty; high cost; reserved for very hard materials |
Practical rules from forum-validated workshop technique:
- Light pressure with carbide — minimal pressure for clear mark. Heavy pressure breaks carbide tips.
- Oil before scribing on machined metal — improves scribe line clarity, makes the line stand out against the cutting oil/coolant residue.
- Store scribers tip-up or in a sheath — dropped scribers chip the tip on the workshop floor.
- Hardened steel scriber is fine for mild steel — don't pay premium for carbide if you're working soft materials only.
- Carbide scriber for stainless / hardened steel — HSS won't mark hardened materials at all.
For workshop layout marking, Bossweld Engineer's Chalk (75 × 10 × 10mm, 50pc) complements the scriber for temporary marks that brush away cleanly — chalk-line layout on rough steel is the typical workshop combo.
Transfer punches — locating mating-hole positions
A transfer punch is a precision-ground straight punch sized to fit exactly into an existing drilled hole. When held inside the hole with the protruding end against a mating surface, a hammer tap transfers the hole position onto the mating part — exact mark with no measurement required.
Transfer punches come in sets matched to standard drill sizes — typically a 28-piece set covering common metric sizes from 3mm to 13mm, or imperial 1/8" through 1/2" in 1/64" increments. Used for: matching bolt-hole patterns between assemblies, copying jig hole positions, retrofitting hardware where original mounting holes need to be replicated.
The technique works because the punch outside diameter matches the hole inside diameter — there's no movement when the punch is in the hole, so the strike point is exactly under the hole centre.
AIMS doesn't currently stock dedicated transfer punch sets but can source on request through the supplier network. The Stahlwille SW108 parallel pin punch sets ($118-$139) cover similar territory for general workshop pin and centre work.
Nail punches — different category (honest scope)
A nail punch is technically a punch but the application is carpentry, not metalwork. Nail punches drive nail heads below the surface of timber or plasterboard — the indentation is then filled with putty or wood filler before painting. The point is flat or slightly concave to seat on the nail head; the punch body tapers slightly toward the working end.
The AIMS-stocked Sutton M709 Nail Punch CRV — Soft Grip series (sizes 1.5-6mm, 3,441 units inventory) covers the standard carpenter and joinery nail punch range. The Sutton M7090005 Nail Punch Set 5-piece (2-6mm) is the bundled workshop kit ($30.83).
For carpentry-specific punches — Sutton M7120500 Flooring Punch 5 × 125mm for floor nail setting, Sutton M7110600 Roofing Punch 6 × 195mm for roofing fastener work — see the dedicated punches and punch sets collection. These are workshop tools but sit outside the centre-punch / pin-punch metalwork scope of this guide.
Sheet metal, hollow, and wad punches — adjacent product class
Brief mention of related products that are sometimes searched under "punch" but are different tools:
- Sheet metal hole punches — hydraulic-assisted punches that cut full holes through sheet metal in one stroke. The Q-Max Round Sheet Metal Punch ($51.94+, 40 size variants), Bramley Chassis Hole Punch ($61.32+), Bordo Chrome Alloy Screw (Chassis) Punch ($72.68+), and Excision 210/16 Round Punch ($54.58+) cover the AU range. Used for: chassis hole punching, electrical enclosure cut-outs, sheet metal fabrication.
- Oblong / shaped punches — same family but with non-round profiles. The Excision 210/16 Oblong Punch ($134.64+) covers slot punching for switch mounting and bus-bar work.
- Hollow / wad punches — cylindrical cutters used to punch holes through soft materials (leather, gasket material, plastic sheet, cork). The Maxigear Hollow Punch / Wad Punches set ($14.21+, 54 variants) is the AU workshop standard. The Maun Wad Punch Metric Set 5-32mm with Centre Punch (10pc) ($225.28) is the UK premium tier.
- Notching punches — see the separate notching punches and dies collection.
These are different tools from the centre/prick/pin/drift punch family covered in this guide — different application, different chemistry, different selection criteria.
Materials guide — what each punch works on
Like files, hardened steel punches can only mark materials softer than the punch body itself. The punch tip is hardened to roughly Rockwell C 58-62 — works on most workshop steels but fails on fully-hardened tool steel and hardened bearing races. Tungsten carbide scriber tips at Rc 90-94 extend the range to hardened steel and ceramics.
| Material | Best punch/scriber | Notes |
|---|---|---|
| Mild steel (1018, 1020) | Standard centre punch + HSS scriber | Workshop default — any punch works. |
| Structural steel (350MPa+) | Standard centre punch + HSS scriber | Works fine — punch tip harder than workpiece. |
| Cast iron | Standard centre punch + HSS scriber | Works fine — workpiece typically softer than punch. |
| Aluminium / brass / copper / non-ferrous | Centre punch + HSS scriber | Marks easily — lighter strikes needed; over-striking deforms aluminium. |
| Stainless steel (304/316 annealed) | Centre punch + tungsten carbide scriber | Punch works; HSS scriber dulls quickly — use carbide. |
| Tool steel (annealed) | Centre punch + carbide scriber | Works when annealed; not after hardening. |
| Hardened tool steel (Rc 55+) | Diamond-tip scriber only — no punch | Punches won't mark; diamond scriber is the only option. |
| Hardened bearing races | Diamond scriber only | Don't try to centre punch — punch tip will chip. |
| Ceramics / glass | Tungsten carbide or diamond scriber | Punches will shatter ceramic. Use carbide scribe + drill bit specifically rated for ceramic. |
| Plastic (ABS, PC, nylon) | Light centre punch or just drill direct | Plastic compresses under punch; mark is shallow but visible. Many plastic jobs skip the punch step. |
| Sheet metal < 1mm | Light manual punch; avoid heavy auto punch | "Starrett 18C too strong, can poke holes through sheet metal" — forum warning. Use light automatic or manual punch with controlled hammer tap. |
AU brand guide — Sutton, P&N, Trax, Stahlwille
| Brand | Tier | Range | AIMS stocked? |
|---|---|---|---|
| Sutton Tools | AU industrial DOMINANT — workshop volume leader | M707 Centre, M706 Pin, M709 Nail (all CRV soft-grip 2-6mm), plus 5-piece sets and roofing/flooring specialty punches | ✅ Full range — massive 9,000+ unit total inventory across SKUs |
| P&N | AU automatic + scribers | 267AP1125 Brass Auto Centre Punch, three scriber variants (270mm dual-end, 150mm tungsten tip, magnetic kit) | ✅ Yes |
| Trax | Workshop value | ARX-ACP Automatic Centre Punch, ARX-HDCP5 Centre Punch Set 5pc, ARX-PCS7 Punch & Chisel Set 7pc | ✅ Yes |
| Stahlwille | German premium | Punch Pin range (8 sizes), SW105-8/6 Pin/Centre 6pc, SW108/6 Parallel Pin 6pc, SW102-5/6 Pin/Chisel 6pc | ✅ Yes |
| Starrett (USA) | US gold standard | 18A/18C automatic centre punches; 124/125 prick punches | Not stocked — source on request |
| General Tools (USA) | US value | Auto centre punches; magnetic scribers | Not stocked — source on request |
| Fowler (Japan) | Japanese mid-tier | HD auto punches — Starrett-equivalent quality at lower price | Not stocked — source on request |
| Eclipse (UK) | UK premium | Automatic centre punches in multiple sizes | Not stocked — source on request |
| Rennsteig (Germany) | German specialty | 250N high-force automatic punch | Not stocked — source on request |
| PB Swiss / Bauman | Swiss precision | Solid centre punches and scribers — fine layout work | Not stocked — source on request |
| Moore & Wright (UK) | UK heritage | Automatic centre punches with documented 60-year service life | Not stocked — typically second-hand market |
| Harbor Freight $3.99 punches | US budget — avoid | Internal mechanism fails quickly per forum reports | Not stocked / avoid |
Sutton Tools dominates AU industrial workshop punch supply — same patriot positioning as P&N files, Macnaught grease guns, Linishall wire wheels. Sutton M707/M706/M709 punch series alone holds 9,000+ units across inventory at AIMS — sustained demand and supply depth confirms the workshop-standard status. P&N covers the scriber range and the brass automatic centre punch — also AU-made, also industrial workshop standard. Stahlwille is the German premium tier for workshops specifying premium hand-tool quality. Trax is the workshop value tier for occasional-use buyers.
AIMS-stocked range deep dive
| Need | Recommended product | Price |
|---|---|---|
| Workshop centre punch — workshop default | Sutton M707 Centre Punch (2-6mm) | From $5.27 |
| Centre punch set — complete workshop range | Sutton M7070005 Centre Punch Set 5-piece (2-6mm) | $29.76 |
| Pin punch — driving pins through holes | Sutton M706 Pin Punch (2-6mm) | From $5.58 |
| Pin punch set | Sutton M7060005 Pin Punch Set 5-piece (2-6mm) | $34.62 |
| Automatic centre punch — one-handed marking | P&N 267AP1125 Auto Centre Brass Punch 125mm | $20.90 |
| Automatic centre punch — workshop value | Trax ARX-ACP Automatic Centre Punch | $15.40 |
| Engineers scriber — workshop standard | P&N 267M06020 Workshop Engineers Scriber 270mm 90° Bend | $8.91 |
| Tungsten carbide scriber — hardened materials | P&N 267M06041 Workshop Scriber Tungsten Tip 150mm | $9.05 |
| Magnetic scriber kit — pickup tool combo | P&N 267QM0550 Magnetic Pick-Up and Hooks Scriber Kit | $22.98 |
| Parallel pin punch — German premium set | Stahlwille SW108/6 Parallel Pin Punch 6pc wallet | $139.15 |
| Pin/centre combination — German premium set | Stahlwille SW105-8/6 Pin/Centre Punch 6pc stand | $112.59 |
| Pin + chisel combination | Stahlwille SW102-5/6 Pin/Chisel Punch 6pc wallet | $182.16 |
| Centre punch + chisel value set | Trax ARX-PCS7 Punch and Chisel Set 7-piece | $35.70 |
| Nail punch (carpentry) | Sutton M709 Nail Punch (1.5-6mm) | From $5.27 |
| Engineer's chalk — layout marking complement | Bossweld Engineer's Chalk 75 × 10 × 10mm (50pc) | $12.47 |
Browse the full inventory in the punches and punch sets collection.
Common centre punch and scriber mistakes
| Mistake | What goes wrong | Fix |
|---|---|---|
| Using only a centre punch (skipping the prick punch) | 90° punch slides off scribed lines — inaccurate mark, drill wanders | Two-stage: prick punch first for accuracy, centre punch over for drill start. |
| Not filing off the raised metal after punching | Drill bit hesitates and wanders around the crater rim | Two strokes with a smooth file flatten the raised metal. |
| Using a heavy automatic centre punch on thin sheet | Punches a hole right through sheet metal — forum warning on Starrett 18C | Use light automatic, manual punch with light tap, or 18A instead of 18C. |
| Heavy pressure with tungsten carbide scriber | Brittle carbide tip chips or breaks | Minimal pressure — carbide cuts on lightness, not force. |
| Using HSS scriber on hardened steel or stainless | Mark won't take or wears out scriber quickly | Tungsten carbide tip for hardened materials. |
| Hammering punch off-axis | Mushrooms the punch head, deforms the mark | Strike directly inline with the punch axis. Small ball pein hammer. |
| Using wrong-size pin punch for pin diameter | Smaller punch slips; larger punch won't enter hole | Match punch diameter to pin diameter exactly. |
| Using a centre punch on hardened bearing race | Punch tip chips against harder material | Use diamond scriber for hardened bearings; don't try to centre punch. |
| Failing to disassemble + clean a "dead" automatic punch | Spent money replacing a working punch with gritty internals | Strip, clean, oil internal mechanism — forum-documented restoration. |
| Confusing centre punch with nail punch | Wrong tool for the job — nail punches have flat tips for nail heads, not cone points | Centre punch for metalwork drilling; nail punch for carpentry sinking nail heads. |
Selection checklist
- What's the job? Marking out before drilling → centre punch (+ prick punch for precision). Driving pins → pin punch. Layout lines on metal → scriber.
- Material hardness? Rc 55+ workpiece = diamond scriber only, no punch. Otherwise standard punches work.
- Sheet metal under 1mm? Light manual punch — avoid heavy automatic. Starrett 18C and Rennsteig 250N are "too strong" for thin sheet.
- One-handed operation needed? Automatic centre punch — P&N or Trax for value, Starrett 18A / General for US premium (source on request).
- Mark hardened steel or stainless? Tungsten carbide tipped scriber — P&N 267M06041.
- Production layout volume? Automatic + 28pc transfer punch set (sourced) saves significant labour vs prick-and-centre two-stage.
- Pin sizes for assembly/disassembly? Match punch diameter to pin diameter — Sutton M706 covers 2-6mm; Stahlwille SW108/6 covers premium parallel-pin work.
- Workshop standard set? Sutton 5-piece centre punch + 5-piece pin punch + P&N tungsten scriber covers 90% of workshop jobs for under $80.
For sizing advice, bulk supply, or sourcing Starrett/Eclipse/PB Swiss specialty punches, contact the AIMS team or call (02) 9773 0122. Adjacent guides: Hand File Guide (filing off the centre punch raised mark), Drill Bit Selection Guide (drilling on the centre-punched mark), Hammer Types Guide (selecting the right hammer for punch work), Keyway Guide (fitting work that uses pin punch technique).
Frequently Asked Questions
What's the difference between a centre punch and a prick punch?
The point angle. A prick punch has a sharp 30-60° point for precision layout marking — placed exactly at the intersection of scribed lines for high-accuracy layout. A centre punch has a 90° point for widening the prick mark into a cone-shaped dimple that guides the drill bit. The two-stage technique (prick punch first, then centre punch over the prick mark) is the workshop standard for accurate drilling. Some specialty centre punches use 118° or 140° points to match drill bit geometry exactly — used in precision machine shop work where drill wander must be eliminated.
What is the angle of a centre punch?
Standard centre punch is 90°. Prick punches (sometimes called dot punches) are 30-60°. Drill-bit-matched centre punches are 118° (matching standard twist drill geometry) or 140° (matching some specialty drill bits). For most workshop drilling, the 90° standard is the right choice — the cone shape lets the drill bit point seat properly and start cleanly.
How does an automatic centre punch work?
The punch body contains a spring-loaded internal mechanism — a heavy mass held under spring tension. When downward pressure on the punch tip exceeds the spring threshold, the mass releases and strikes the tip from inside the body, delivering a consistent hammer-equivalent blow without needing a separate hammer. The tension cap on the rear of the punch allows force adjustment. Most automatic centre punches are pre-set to a workshop-standard strike force suitable for general steel marking.
Centre punch vs pin punch — what's the difference?
Centre punches have tapered conical points (90° for centre, 30-60° for prick) used to mark or indent metal. Pin punches have parallel cylindrical bodies with flat tip faces — used to drive roll pins, dowel pins, spring pins through holes during assembly and disassembly. Different jobs entirely: centre punch creates a mark; pin punch transfers force through a pin.
Pin punch vs drift punch — when to use each?
Drift punches have a tapered front section narrowing to the working tip — the taper provides initial strength for breaking a stuck pin loose. Parallel pin punches are fully parallel from end to end and are used after the drift to drive the pin through the hole. Workshop technique: drift first to break the pin free, then switch to parallel pin punch to drive it through.
Is a centre punch the same as a nail punch?
No. Centre punches have tapered conical points (90° or 60°) for marking metal before drilling. Nail punches have flat or slightly concave tips for driving nail heads below the surface of timber or plasterboard. Different application entirely — centre punch for metalwork, nail punch for carpentry. AIMS stocks both ranges from Sutton (M707 for centre punches, M709 for nail punches).
What is a transfer punch?
A precision-ground straight punch sized to fit exactly into an existing drilled hole. When held inside the hole with the protruding end against a mating surface, a hammer tap transfers the hole position onto the mating part — exact mark with no measurement required. Sold in sets matched to standard drill sizes (typically 28-piece sets covering 3mm to 13mm metric or imperial 1/8" through 1/2" in 1/64" increments). Used for matching bolt-hole patterns between assemblies, copying jig hole positions, retrofitting hardware.
What is an engineers scriber?
A hand tool with a hardened-steel or tungsten-carbide-tipped point used to draw layout lines on metal surfaces. The hardened tip cuts a thin line into the metal — more permanent than pencil or marker, visible through metalworking fluids, locatable by feel as well as sight. Standard engineers scribers have a knurled grip and a 90° bent tip on one end for inside curves. Tungsten carbide tipped scribers extend the range to hardened steel and stainless.
Tungsten carbide vs hardened steel scriber — which is better?
Depends on the material. Hardened steel (HSS) scriber at Rc 60-65 marks mild steel, aluminium, brass, copper and soft non-ferrous metals — cheaper, but tip wears with use and won't mark hardened steel or stainless reliably. Tungsten carbide scriber at Rc 90-94 marks hardened tool steel, stainless steel, ceramics, glass and all softer materials — more expensive, brittle tip (chips if dropped), needs only minimal pressure for clear mark. Rule: HSS for soft workshop work, tungsten carbide for hardened/stainless work.
How do I mark out for drilling on metal?
Standard workshop sequence: apply layout fluid (engineer's blue) to the workpiece face; scribe layout lines with sharp scriber + straight edge; prick punch at line intersections for precise marks; verify marks with magnifier; centre punch over the prick mark to widen the cone for drill bit start; file off the raised metal around the punch dimple; drill on the flattened mark. The two-stage prick-then-centre approach plus the file-off-deformation step are the workshop standards that separate accurate drilling from drill-wander rework.
Why do I need to file the punch mark before drilling?
Centre punching deforms metal upward around the dimple — the punch displaces material rather than removing it, so a raised crater rim forms around the dimple. The raised metal makes the drill bit hesitate, skip, or wander as it tries to start cutting on uneven surface geometry. A few quick strokes with a smooth file flatten the raised metal and leave a clean dimple in a flat surface — the drill bit point seats properly and starts cleanly. This single technique is the most-skipped workshop step and the number-one cause of drill bit wander after centre punching.
Why is my drill bit wandering off the centre punch mark?
Three likely causes ranked by frequency: (1) the raised metal around the punch dimple wasn't filed off — file the high spot flat; (2) the punch mark is shallow or off-centre — re-punch deeper and verify position; (3) the drill bit isn't sharp — a dull drill bit walks across surfaces regardless of how good the centre punch mark is. For thin sheet, also check that the drill bit point angle matches the centre punch angle — if the punch is 90° and the drill is 118°, the drill point edges contact before the centre point seats, encouraging wander.
What's the best automatic centre punch brand?
Forum consensus across Practical Machinist, Hobby-Machinist, Garage Journal and Home Shop Machinist BBS: Starrett 18A is the US gold standard ("lifetime tool" where it works), General Tools is the practical workshop choice at lower cost, Fowler HD (Japan) offers Starrett-equivalent quality at ~$22, Eclipse (UK) and Rennsteig (Germany) are premium European alternatives, Moore & Wright UK punches have documented 60-year service life. AIMS-stocked AU options: P&N 267AP1125 brass auto centre punch ($20.90) for workshop standard, Trax ARX-ACP ($15.40) for value tier. Avoid Harbor Freight budget punches — forum-flagged as compromised quality.
Can I use a centre punch on hardened steel?
No — standard centre punches at Rc 58-62 can't mark hardened steel at Rc 55+. The punch tip will skate across the surface or chip. For marking hardened tool steel, hardened bearing races, hardened stainless or similar materials, use a tungsten-carbide-tipped or diamond-tipped scriber instead. The carbide scriber cuts where the steel punch can't deform.
Does AIMS stock Starrett centre punches?
Not currently in stock — Starrett 18A and 18C are sourceable through AIMS supplier network on request. AIMS-stocked alternatives that cover similar workshop scope: P&N 267AP1125 brass auto centre punch ($20.90), Trax ARX-ACP automatic centre punch ($15.40), Sutton M707 manual centre punch range ($5.27+). For Starrett, General Tools, Fowler, Eclipse, Rennsteig, PB Swiss or Moore & Wright punches, contact the AIMS team to discuss sourcing.