"DoN. Nichols" wrote in message
...

Very awkward, as I don't see how to make split nuts with a ball
race in them -- hmm ... maybe I *do*, but they would be quite expensive.

I've been thinking about this more and more. This is hard to describe but
here goes:

What if I could mount the ball nut in such a way that the normal split-nut
control would allow the ball nut to rotate freely when in the dis-engaged
position, but grab-on to the outside of the ball-nut when in the engaged
position. You'd also probably have to trap the ball nut along the leadscrew
direction somehow (with thrust bearings on each end or something like
that...)

I could almost do this with the split-nut mechanism that my lathe already
has. The current design has two brass halves of a nut that are forced
together when you swing the control lever down. I could mount the ball nut
to something that fits into this space (for the sake of this
discussion...let's just say it is a thick walled round tube. The inside of
the tube is big enough to clear the leadscrew completely). The ball nut
would be bolted to this tube. I'd replace the brass nut halves with
something that would grab the outside of the tube securely, and the tube
would be inserted inbetween these grabbers.

When I swing the control level down, the tube (and the ball-nut that is
bolted to it) would be stopped from rotating, and would then start to drive
the table. When I swing the control lever up, the ball-nut would once again
spin freely and the table would stop.

I don't know...sounds a little messy...but with a little attention to detail
it might actually work.

Todd