In article 1133335342.174333.5720
@g47g2000cwa.googlegroups.com,
says...
what are the advantages to a taper pin as opposed to a normal pin, or a
grade 8 bolt? would the pin be behind the collar or through it?

It's easier to get a good locational fit since you ream the
pin hole with the collar in place and the taper makes it
easy to produce an interference fit in both parts. Also
easier to assemble and disassemble than a tight fitting
straight pin since it only takes a few taps to seat or
unseat the pin.


The collar will be the platform for a roll bender die setup and it will
be subjected to a thrust load, so I was considering cutting into the
shaft to make a notch for a heavy duty clamp collar to sit in. so say,
buy a collar for 1.375" or 1.25" shaft and turn that notch into the
1.5" shaft. that baby would never move, right?

The collar mfrs publish data on the thrust required to move
the collar...
http://www.staffordmfg.com/pages/engdata_body.htm#5


The shaft could be
ordered with a keyway full length, and I could settle for tapped holes
in the ends rather than stepped down thread. Also, easy to
replace/service if it all crapped out on me..

Definitely easier if you don't require close concentricity
and the threads are somewhat smaller than the shaft. Tap
the ends and screw long alloy hex socket set screws into
the holes til they bottom out.

Ned Simmons