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Newsgroups: rec.crafts.metalworking
Subject: Re: 3c Expanding Collets for internal holding
From: Robert Bastow <"teenut"@>
Date: Thu, 27 Jan 2000 20:13:35 GMT

I have never seen the beasts..but they are simple to make..especially if you
have access to the, holding a through bore.

Chuck a suitable sized stub of suitable metal and turn down about an inch in
length to a square shoulder.  Reverse this in chuck or collet and turn down to
within a few thou of your bore size and to suitable (Bore) length..again to a
sharpe shoulder..leaving about 1/8" of shoulder between the two diameters.  

Drill right through and tap a suitably sized fine thread.  Countersink the bore
to a 60 deg included angle.  

Center punche the shoulder at no 1 jaw position, so that you can replace it
accurately and remove the stub collet from the chuck.  Make or modify a hex
socket cap screw by machining th underside of the head to match the 60 deg

Slit the stub collet right down to the collar..if it is a partickularly "stiff"
one, you can first plunge a parting tool groove adjacent to the shoulder to make
the "wings" more flexible.

Replace the stub in the chuck, aligning the pop mark with #1 jaw.

Now skim it down to a close slip fit in your component bore.  Put in the
expander screw and away you go.   It will hold concentricity as well as any
"Boughten" collet.


Bob wrote:
> Ok... I've looked high and low.  Everyone sells a set of 5c expanding
> collets, and there are some arbor sets (the largest, at 1", is too small
> for my needs).  I've scoured Hardinge and other sites, but alas, no
> luck.  There are plenty of "step" type collets, but... ???
> Is there such a thing as expanding collets for internal holding for the
> 3c collet system?
> Thanks... Bob

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