Re: [CAD_CAM_EDM_DRO] size of leadscrew question

> > The table I have in mind will have a 48" cutting length X axis, so figure 5
> > to 6' long. Could I substitute a 1/2" leadscrew with 10tpi and 2 starts?

Here is what you can expect from a 1/2" leadscrew that moves a nut at 1", per 2
turns, at 60" long. You will be able to very comfortably run Rapids as high as
250ipm without too much concern for the wobble syndrome. Beyond that, that small
of a diameter will wobble. I have run my machine with that setup as high as
600ipm with quite a bit of wobble, even though both ends are set in the proper
bearings and tensioned slightly. Pushing the envelope, Some of the wobble will be
taken up as the nut itself moves to the center area of the lead screw. A small
amount of wobble has shown no disasterous effect over time.

I used to look at all the heralded "Rapid Rate" capability, but over time have
dismissed it as being something you need ONLY if you really need it. I really
have not met any hobbiests who really need even 500" per minute on a contact
cutting type tool. Production Shops.... Sure. They need it. In the hobby shop it
can be dangerous.

If I was to replace my 60" long Screw, I would increase the diameter to a 3/4"
screw. But, if costs have you counting pennys, you can run the 1/2" and replace
it some day. Just make your design have enough room to allow for it later on.
When it becomes time to swap it, you really do not have any problems getting back
a good chunk of your money on the old screw when you sell it on E-Bay!

Keep in mind, I am speaking of a 1/2" "lead" screw (2 turns per inch). If you
drop that to .200, you will have the "wobblies" show up well under 200ipm over
that length of screw. As far as capability, I do not have the Kerk Nut specs in
front of me with the data, but it will be a really long time before you actually
"wear out" an Acetal antibacklash nut if you go the route of a smooth rolled lead
screw..........

Chris L