Hi Chris,

I have made some spare collets to be able clamp some odd diameter work, I just used silver steel and didn't harden/temper it. Since the silver steel is harder than mild steel even if not hardened my homemade collets have survived for many years. You could probably use something like EN8 or EN24, not as easy to machine as EN1A of course.

I assume commercial collets are hardened, tempered and ground.

Thor

I've made split one way, threaded shank 15 degree taper collets for my trent pinion mill in the past, and I made these all out of 19mm .303 stainless steel. I've never had a problem with them,

I machine the body first, backwards facing so that I can finish with the screw cut for the shank, otherwise I can't grip the taper backwards to machine it due to the angled face, so I drill to size whilst machining it and finish with a reamer, once I've parted off I would then stamp the size on the face with very small 1.0mm number stamps, this has to be done in a quick 15 degree angle jig I made, and before the splits are machined so as to not damage the collet whilst stamping.  Then I use a small slitting saw and rotary table on the mill to split the collet, then it is finished. 

As you can tell, I got this process down to the tee eventually because of how many I needed to make. 

Like others have said, if I was going to make a much bigger collet that would fit my MT4 lathe, then i'd probably use EN8, I wouldn't bother with any treatment for what we do.

The professional ones are always ground rather than machined these days, and are probably always some kind of nickel bearing alloy steel.

Michael W

Edited By Michael-w on 31/07/2017 21:25:36