Find a duplicate collet and practice on it to see what works best.

Collets can be extremely hard and they are also flexible which makes working on them quite difficult

As mentioned, grinding is probbly the way to go

Just a thought…wouldn't modifying the key be better…only one to do rather than a set…

It's in pretty deep but could be coaxed out and ground down…

Ken. Are you sure that these collets have the same profile?

The angle at the thick end for example?

At one point I inherited an Aciera F1 and found that this company:

http://www.floydautomatic.co.uk/products.asp

actually make collets, in fact they make Schaublin ones, so maybe they could make some with a longer keyway? They are based in Baldock, Herts. I seem to remember that their W20 ones seemed quite reasonably priced, so may not be prohibitive to get specials especially since it's a small variation. Could even be a niche product for them as there are enough Pultras around, I bet they have been asked before.

John.

dubble post

Edited By Ady1 on 08/09/2014 21:40:19

I think you will find that collets for the Smart & Brown lathes,…the models L and A, will also fit the 'big' Pultra as both are 20mm and made by the same company(Pultra now defunct)

You are the daughter of Godzilla and I claim my five pounds!

graham.

I have the feeling that I read somewhere about modifying collets with a carbide cutter.

I don't know if you were thinking of my recent use of a carbide indexable tool for cutting a hardened steel ballscrew housing but some of the common grades are indeed rated for working hardened steel. You have to run the piece at the specified surface speed and take proper (but light) cuts but if you don't mind setting fire to yourself and your workshop, it may be worth trying. The limitation may be getting your machine to deliver enough power at a high enough speed for the tool to cut properly. The advantage is that you don't need to anneal the work or use a grinder and it's reasonably quick.

My experience was with the flange of a hardened ballscrew of around 2" diameter that needed to be turned down to about 1.2" on the Bantam which has something like a 1.5HP motor. I think I was using in the region of 1800-2000 rpm (ie slightly overspeed) and power feed with carriage stop. The final result was clean and accurate and cost me almost 2 inserts (3 edges out of 4). The sparks were mighty.

My main concern would be the workholding, given the spring of the collet jaws. I have no idea if that is a problem.

There are a couple of photos of the process in one of my albums near the bottom.

Murray

Have a look here:

I bought one from a famous auction site for £15 and have found it useful for the sort of job you want to do on hardened steel.

Matt

I just resurrected this thread to see if anyone did manage to lengthen the keyway slot on a collet.

I have the same problem as the OP, my collet is a 15mm shank Boley, one of a number of Crawford & Boley collets that came with my lathe and the one I want to use won’t draw in as it’s keyway slot is 5mm shorter than the others for some unknown reason.

I guess grinding is the only option here, the original OP doesn’t seem to have visited the forum lately so might not hear from him.

Yes or the more common T slot / woodruff cutter in carbide. you dont mention the width but the typical 4mm wide cutters are about £4 on your favourite site