Subject: Collet Question

From: [email-masked] (Vincent Iorio)
Date: 6 May 1994 17:49:50 -0400

I have a question about collets.  I hope some one can help.

I know that I can use 3AT collets on my Craftsman 12" lathe with #3
M.T. in the headstock.

Question - Is a 3AT the same as a 3C?  If not, can I use 3C collets?

Question - Has anyone ever used a spring collet system?  I have seen
it in the MSC catalog and several other places.  It's expensive, but
you can use the same collets on a lathe and a milling machine because
the sell "arbors" for #3 and #5 M.T. and R-8 (and ISO 30,40,50).  It
seem that in the long run I would save money because I need only the
one set.  One person I talked questioned how much "purchase" area or
grip they had, does any one know?

Question - Has anyone use Morse Taper collets? I have seen #2 and #3
here and there.  I'm concerned that the collet is harder then the
shaft on my lathe that I could do damage by drawing the collet in.
Any comments?

Thanks for any info. If I get enough I can organize it and send it to
whoever organizes the FAQ.

					     Vince

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From: [email-masked] (Joe Landau)
Date: Fri, 13 May 1994 05:19:25 GMT

In article <[email-masked]>, f.w.kerfoot..iii ([email-masked]) writes:
>From article <[email-masked]>, by [email-masked] (Clive Washington):
>> In article <[email-masked]>, [email-masked]
>> (Vincent Iorio) wrote:
>> 
>> I assume you mean collets that are closed by drawing into the morse taper.
>> 
>> I have seen several amateur designs for this system, but have never
>> tried it.  The main problem is that a morse taper is so slow that it
>> would not self-release when the axial force was removed.  If the
>> collet jams, you have to hit it from the rear to detach it, and this
>> is no good for the mandrel bearings.  The commercial collets I have seen
>> use a much faster taper (20-30 degrees), and these release without
>> persuasion.

I _think_ that a taper is self-releasing if the coefficient of friction is
less than the tangent of the taper angle.  Looks reasonable on paper. 
Perhaps someone more knowledgeable than I can verify or correct.

--Joe Landau