Logo

Why Forge Your Own Punches and Chisels

There is a particular satisfaction in reaching for a chisel you made yourself, knowing the steel is sound and the temper is where you want it. Shop-bought tools are made to a price point and a generic specification; your own can be shaped to suit your hand, your hammer, and the work you actually do. A punch with the exact taper you prefer, or a hot cut with a bevel angle that slices cleanly through 20mm bar, is a tool that earns its place on the rack.

More practically, punches and chisels are consumables. Tips blunt, edges chip, and shanks eventually mushroom. Being able to reforge, re-harden, and re-temper them keeps you working instead of waiting on a delivery. It is also one of the best exercises in heat treatment a smith can do, because the results are immediate and unambiguous: a chisel either cuts or it does not.

Choosing the Steel

You want a steel that hardens readily and holds an edge at temperature. Water-hardening tool steels are traditional for this work — the old EN9 and EN42 grades, or the modern equivalents sold as gauge plate and silver steel. Silver steel (a bright, centreless-ground carbon steel around 1% carbon) is excellent for punches and small chisels, though it is unforgiving if you quench it carelessly.

Salvage works beautifully too. Coil springs from cars, old files, and hayrake tines are all high-carbon and forge into fine tools. A file makes a superb hot cut, though you must anneal it first — heat to bright red and bury it in ashes or vermiculite overnight — before you file, grind, or forge it, or it will snap.

• Hot cuts: medium-carbon steel, tempered fairly soft. They run hot and are not expected to hold a razor edge.
• Cold chisels and punches: higher carbon, harder temper. These need edge retention at room temperature.
• Drifts and slitters: tough, moderately hard steel that resists bending more than wear.

Forging a Hot Cut Chisel

Start with a bar around 200–250mm long and 20–25mm square. Draw out one end to a taper, working it evenly so the transition is smooth rather than stepped — a sharp shoulder is a stress riser that will snap under the hammer. Bring the tip down to roughly 8–10mm wide and about 3mm thick, then forge the cutting edge.

For a hot cut, aim for an included angle of about 50–60 degrees. That sounds blunt, but hot steel parts easily and a thin edge will fold and burn in the cut. For a cold chisel, go a little steeper at 60–70 degrees. Work the bevels from both sides so the edge stays centred; an off-centre edge will steer the cut and wear unevenly.

Leave the striking end alone for now — do not forge it to a point or mushroom it deliberately. A slightly domed, softened head is what you want. If you fancy a handle, forge a short tang, but many smiths simply hold hot cuts with tongs or set them in a wooden handle that can be knocked off.

Forging Punches

Punches come in more shapes than most people realise, and each has its own logic. A round punch for drifting holes is tapered along its length, so it can be driven through and then released. A slot punch is flattened and widened to open an oval hole. A centre punch has a short, steep point. A hot punch for decorative work might be shaped to leave a specific mark.

Whichever you make, taper the body gently. A punch that is parallel-sided will jam; one with a slight taper from tip to shoulder will come free with a twist. The tip should be flat or very slightly domed — never needle-sharp, because a fine point simply burns away in hot metal and gives you nothing. Dress the working end square and smooth before heat treatment.

Hardening and Tempering

Heat the working end to a good cherry red, around 780°C. The reliable test is a magnet: carbon steel goes non-magnetic just above its critical temperature, so bring it to non-magnetic and then a shade brighter. Do not overheat it to orange or yellow — you will grow the grain and end up with a brittle tool.

Quench vertically, tip first, in the right medium. Water or brine for EN9 and silver steel; oil for oil-hardening grades and salvaged spring steel. Plunge straight down and move it gently — a sideways entry warps the tool. Hold it under until it stops hissing, then pull it out while the body is still warm to the touch.

Now temper. Polish the tip back to bright metal with emery, then heat the shank behind the tip and watch the oxide colours run towards the edge.

• Cold chisels and cold punches: quench when the tip reaches pale straw to straw, roughly 220–240°C.
• Hot cut chisels: let it run to brown or purple, around 260–290°C. Softer, tougher, and perfectly capable of cutting hot steel.
• Hot punches: purple to blue, 280–320°C, so they deform rather than shatter when they meet hot metal.

As soon as the colour arrives at the edge, quench the whole tool in water to stop it running further. Then block-temper the striking head: heat it to blue-purple and let it cool slowly, so the hammer end is soft and mushrooms safely instead of chipping.

Finishing and Testing

Grind the final bevel after tempering, keeping the tool cool with frequent dips — a blue patch on a freshly sharpened edge means you have just undone your tempering. Stone the edge, oil the body against rust, and fit a handle if you want one.

Test on scrap. A good hot cut shears through bar with a firm hammer blow and a clean sound. If it dents and rolls, it is too soft; if the edge chips out, it is too hard — re-temper and try again. Every tool teaches you something, and the second one is always better than the first.