Re: spinning ball nuts

> That "design challenge" will indeed be the "SNAFU"! I still think

you will

> need AT LEAST a 1.25" O.D. screw! I built such a machine in '86
> (126"-"X-screws") and I DID use 1.5"O.D. x ½" pitch ball-screws.

Expensive, yes, but it

> worked!
>

Jan -Thanks for your help. I'm curious why you think still a 1.25"
screw will be needed. This has HUGE load carrying capability, far
more than the couple of hundred pounds tension (at most) load exerted
on it by moving the carriage , even while cutting. Seems all I'll
want to do is have a screw stiff enough to not sag appreciably when
the carriage is at the extreme either end. And even a little sag
would be OK from a positioning perspective, as the screw would
be "lifted" into place as the carriage (a rigid system, much more so
than any sag seen in the screw)passes by. The need for a 1.25"
SPINNING screw comes from the effect of it whipping like a jump rope
at high RPMs if it's not rigid enough (overcome by upping it's
diameter as the unsupported span increases).
I will plan on incorporating a tensioning rig onto one end of the
stationary screw (I'll have a VERY rigid 2"x4" welded steel box beam
machine frame) to hopefully find a good tension that doesn't deform
or unduly stretch the screw while still offering a straight, sag free
push-me pull-me system.
Again, thanks for your insight, and please offer me any corrections
if I've misinterpreted or overlooked anything you've offered.
To all other replies to my inquiry, thank you all. I feel much
better about this approcah with the bits and pieces of your collected
experiences.
Best Regards -
Scott