According to Steve Lusardi :
That is not a shear pin. It is an assembly pin. I have made many drawbars
and I have tried turning them from solid bar. This usually fails unless the
steel bar has been totally normalized (annealed). Even with a follower rest,
the bar bends as its diameter is reduced. So, it is much cheaper to pin a
Hex on a piece of hotroll bar and thread the other end. Normally a solid
straight pin around .150 is used.

Hmm ... you might be interested in the drawbar for my Nichols
horizontal mill's vertical attachment. It consists of two parts:

1) The bar, with two different threads on the two ends -- one to
mach either of the common 40-taper holders threads.

2) A cylindrical piece, about an inch long, with different threads
in each end, and with a pair of opposed flats milled in the
middle.

So -- you swap ends on both pieces, and it serves as a drawbar
for the other style of thread.

You could mill three pairs of flats to give a final hex if you
so desired.

Obviously, if you are talking R8 collets, this is not a problem,
but someone somewhere up-thread mentioned 30-taper collets -- similar
enough to 40-taper so the problem might exist there as well.

Enjoy,
DoN.

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