Jim Wilkins wrote:

For short lengths a 5C spin index should work well.

The entire length of the finished part is octagonal. Yes, I
could make it out of round stock in this manner, but then
would have to move to the lathe to part off, or hack saw
off. While quantities are low by production standards, I
could be making up to 100 pcs in each of three different
sizes, and that would be a big pain. Also, we're looking at
multiple grooves, or finning, just as a way to reduce
weight. If the part was already to length it would require
handling twice, turning the part around in the collet.
If I had an 8" length, I could proceed to make the part
complete in one smooth process. I'd just be changing 'bars'
a lot more often that I'd originally wanted to.

For perspective, this is for a high tech violin bow made
from carbon fiber. Customer is going to the expense of
buying 5-40 threaded titanium screws from Germany and having
me make as light an aluminum knob for the end as we can, all
to shave another gram or so. It's a production process, the
focus is on end results, not cost. Yet, we don't have
anywhere near the volume to justify custom extrusions.

Appreciate the input though!

Jon