Re: [CAD_CAM_EDM_DRO] Re: collets

Lew,
I'll have to second this one, as all I've been doing for the last 2
weeks is making collets for an obsolete Czech universal mill.
Personally, I have found 4340 stressproof mechanical tubing to be an
excellent choice, much better than 4140 with the added bonus (for ME)
that I do not have to worry about drill wander over the 29" length of
the collet.
Damnedest thing I've seen, 20" draw bar on a 29" long collet. The
spindle bore is trumpet shaped and has 16" of contact surface for
compressing the collet.

Sorry for the ramble, but hopefully it helps.

Iain

dkowalcz@... wrote:

>
> Lew,
>
> Well, here's how I've made collets:
>
> 1. Chuck up a bar of "stressproof" steel. This is steel that has an
> artificially high yield point so that it bends a little farther
> without taking a "set". Threads and finishes well as a bonus.
>
> 2. Do the ID clearance bore first, then turn the OD and seating
> taper, then thread and part off. Leave a solid plug where the
> gripping surface will be.
>
> 3. Re-chuck, zero it out, and bore to the basic size +.005 or so,
> then generate the nose taper.
>
> 4. Cut the slots with a slitting saw on a regular mill. It's
> typically easier to cut 4 slots than 3 if you don't have a dividing
> head, and works just as well.
>
> It's fine to just copy the socket seating angle on the collet in
> most cases. Some folks like to add an extra degree or two there, but
> IMHO that's not worth the effort as it really doesn't change much at
> clamp-up.
>
> Yours,
> Dave Kowalczyk
> TurboCNC software at --> http://www.dakeng.com
>