What steel to use for a punch ?

[Smallfry]

I need to mark the centres of some locating pins on an engine adaptor plate I am making.

I have metric and imperial transfer punches, but the master has blind holes. So I put a couple of old locating dowels in the lathe and turned them down so the ends looked like the ends of the transfer punches. The steel seemed quite soft, so I thought I would harden them by heating to bright red hot, then quenching, which is the method, as I understand. Didn't bother with tempering, as it was one use only.

Put the modified dowels in the casting, and turned it over onto the steel plate, the gave the casting a whack, to mark the centres on the plate. Unfortunately didn't work, as it just flattened the points on the dowels.

Can I use a different grade of steel, silver steel perhaps, to repeat this process more successfully ? Will I still be able to turn some points on it with the lathe, and will I need to harden it afterwards ?

Any suggestions ?

 

[Kram]

Silver steel works well, easy to harden. Tempering is generally a good idea, if it shatters it could get stuck. Qunch hardened steel can be glass brittle without tempering - just stick it in oven with your dinner at 200c.

HSS lathe bits also work well, you wont be able to harden or soften it with a normal torch but a lathe with carbide can turn it ok.

If you have tig, you can weld a hard point on mild steel using drill bit as filler then grint or turn a point. Temper at 500c before you turn it (blue/purple).

If they are threaded holes, point grub screws.

Slightly more expensive but worthwhile option is a screw set.

Transfer Screws - Arc Euro Trade

Transfer Screws are used to transfer hole locations from parts with threaded holes and especially useful with blind threaded holes.

www.arceurotrade.co.uk

 

[Parm]

In this situation an over sized broken tap, turned down to a point will work

 

[Kram]

As would a broken drill bit (more choice of sizes). Cut it off just before the flutes end as that part is still hard, shanks usually soft.

 

[Ian X]

Silver steel rod of size required, easy enough to heat treat and as long as it's not for production work it will do the job just fine.

 

[iNf]

Cut the head off a masonry nail, spin in drill chuck against an abrasive wheel/ belt to a roughly 60° point.
Turn any suitable steel to the diameter and length required, drill hole the diameter of the masonry nail and loctite/glue
the nail in. You can make transfer punches of any diameter/length you require.

 

[Smallfry]

Thanks guys. Some great suggestions.

Didn't even think of old drills, taps, and masonry nails ! I will go and have a rummage and see what I can find ! Would much rather repurpose than buy something new.