Wow! Thanks for that Ned. So a collar with a mere 5/16" bolt
potentially will hold 3000lbs. This is a medium duty machine so I think
that's good enough. Oh wait, what about knurling the shaft where the
collar is positioned? I would guess that it would definitely improve
the "bite"... right? it's easier than cutting into the shaft.. and in
the end.. it's better for something to give a little instead of snap
and fly I suppose.

ok, Compare a mounted roller bearing and a mounted ball bearing. The
dynamic load capacity is pretty much 2 to 1 in favor of the roller
bearing. Information from mcmaster.

I'm using flange mounted ball bearings and they have a 7200 lbs.
dynamic load capacity. there will be six total working against the same
load and this machine's tension force is by a hand operated screw
leveraged by a sliding 36" or so handle. maybe less. The double set
screw in each bearing is also somewhat needed to keep the shaft from
moving in this situation. BUT... question:

Do you think it would hinder the proper function of the ball bearing if
there were press fit bronze sleeves contacting the shaft where it
passes through the heavy plate that the bearings are attached to?? my
theory is that the bronze bearing will take some of the stress from the
load perpindicular to the shaft which is on the end, between the collar
and threaded end. flawed?

- LP