Yeah, Don. Going in to this project, I would have guessed the littlle
collets were buttresss threaded but upon close examination they proved to be
ordinary 60 degree threads. I suppose in such small sizes there is not
enough loss in strength, standard over buttress, to justify the extra
complications of "square" threading. I would expect larger collet threads
to be more square; however I think 5C's are 60 deg. (not that I'm going to
try to make any).

Bob Swinney
"DoN. Nichols" wrote in message
...
According to Robert Swinney :

[ ... ]

Later I decided to make some WW square and hex collect blocks to use with
the small Sherline vise. Having a set of WW collets from 1/64 through
5/16
", the quick set-up collect blocks seemed like a good addition to my
Sherline collet set. So I set out to make everything on my big lathe,
using
5C collets for good centering. Turning the 20 degree collect nose tapers
in
the blocks was a piece of cake but then, Bam! Trouble reared its ugly
head.
I had no tap to thread the WW collect opening in the drawbar for collect
closing. What to do? Careful measuring revealed the thread to be 9/32 -
40. Human, that's a strange one. None were found in my tap drawer. OK,
let's look in the catalogs and buy one - none listed in 3 or 4 catalogs,
none shown in McMaster-Carr on line.

To add to the fun -- that is not a normal thread form It is a
buttress thread. Look at a collet under magnification to see what it
looks like.

Here is an eBay auction selling them:

8921767285

He also sells the taps for the 10mm (D size) collet drawbars as
well. (Hmm ... he specifically says that the 10mm is a buttress thread,
but does not for the WW collets, so I may be wrong.)

Enjoy,
DoN.

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