Chasing punches

(12/07)

Chasing punches, for Peter.

Notes on punch-making, so I don't lose them:

I got punch steel from Phoenix Steels. They were helpful on the phone and shipped quickly.

My square punches are made from their key steel, prices here. Key steel seems to be a rather variable thing, depending on the supplier, but theirs is a suitably hardenable steel.

The round ones are made from silver steel, prices here. They were helpful on the phone, and shipped my order quickly & efficiently. If you find a better source, please let me know.

Most of my punches are made from 4 & 5mm stock. But I've been working very thin metal - half a millimetre - on postage-stamp size bits. You might need larger and sturdier punches for larger work on thicker stock.

I only use round stock for punches with round ends. Otherwise, I always use square stock, because that makes it easier to control the angle of the tool when you're using it.

I only came across one place selling ready-made punches in Europe when I was searching, and that was Fischer. They have a vast array of shapes, at not-terrible prices, and they seem to be quite efficient. But, I keep needing new shapes while I'm working on something, so getting the punches by mail-order would be frustrating. I ordered chasing pitch from them (the black one, not the red one), and have been very pleased with it. Their web site can be a bit impenetrable, and it may be worth downloading their PDF catalogues to get more detail.

Oh - and they have punch blanks too, which is a bit more expensive than buying square tool steel, but would be very convenient.

You'll find plenty advice on making chasing tools on the web, espcially at Ganoskin. I am by no means an expert, but this is what I do.

Cut your steel to length with a hacksaw. My tools are all 90mm long. If you keep them the same length, you can store them all upright in a can and see all the working ends at once, which is convenient.

File the end to shape. You need to hold the tool in a solidly-mounted vice, and you need a decent-sized fine file, not a needle file. You'll also need a fine round file to make curved liner punches.

The round punches can be done more quickly on a lathe, if you have access to one.

Round the end with emery cloth (240 grit or so).

Then smooth it with 400 and then 800 wet-and-dry paper.

Polish with Autosol (from Halfords) on folded-up kitchen paper, or use a steel-polishing compound like Carbrax on a felt wheel.

Once you are happy with the shape and polish, it's time to harden.

Get an old tin full of cold water.

Hold the steel with pliers, and heat the working end to a bright red with a blowtorch.

While it is still red, drop it into water. Now it is hard, but very brittle. You need to temper it, which makes it a bit softer and a lot less brittle.

Clean the sides of the tool with 800 grit wet-and-dry till you can see metal, then start heating the tool an inch or so back from the working end.

You will see colour start to move down the tool. As soon as the working end is straw-coloured, drop it it into water.

(If you heat it too much, you will have softened the tool, and you need to re-harden it before you can re-temper it)

Now, polish the working end again. You may need to use 800 grit wet & dry on it first, if it has black scale on it.

That's it. Now go chase.

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