re:Re: Timing Belts vs. Rack and Pinion drive

Terry wrote:

>How do you support the leadscrew on a large machine? A 3/4" dia. x
>10' long leadscrew will have considerable sag when the gantry is at
>one end of the machine.

Simple answer first. You Don't.(3/4 is too small for this distance)

But...

You could rig supports(like a lathe steady or follower rest)
which "fold"(or roll, or drop) out of the way when the gantry is near.

Or...

You could let the screw sit in a 1/4 circumference "trough" and use a
nut that is only 3/4 circumference. (like thomson fully-supported
shafting and ball-bushings). "trough" could be moglice!

else...

Spin the NUT. And tension the 3/4 screw so it doesn't sag. (This
solution is actually used on several commercial machines )

Hope this helps.

Ballendo