backlash comped nut design re:Re: Ball screws for CNC plasma cutters

Smoke,

ANOTHER design which WILL fit, and takes advantage of
leadscrew "flank angle" is as follows:

What we're going to make will look a LOT like a 5C collet (and most
other ??WW?? collets of similar "type" as well).

1)Chuck some round Bar stock several inches long in the lathe.

2)Keeping the 5C picture in your minds eye, turn the diameter down
for a couple of inches(to the point where the 'flare' begins.

3)Thread this outer diameter with your chosen mounting thread for a
short distance. (Check out the ballscrew catalogs and use the thread
which will be used if you convert to ballscrews later.)This will
correspond to the outer "holds it in" thread on the end of the 5C.

4)Drill through and tap for your leadscrew.

5)Now turn the part around in the lathe, and chuck on the small (just
turned) diameter. Set up for an angle cut(taper or compound) and make
a nice "ramp" from the inner dia. to the outer dia.

6)Part off, leaving a short 1/8 to 1/4" 'land' at the major diameter.

Now, slice from the "fat" end towards the mount thread (again, think
5C collet) Two cuts will create four "fingers".

What we do now is use a coil compression spring around the outside of
the nut. When the nut is mounted to the machine, the spring will be
captured between the nut mounting surface and the tapered "ramp".
This will have the desired effect of "closing down" the fingers on
the thread, removing backlash in the process! The "flank angle" of
the leadscrew will work in our favor, and the action will continue to
adjust for wear...

Cool, huh?!

Problem is, there's no adjustability in this "basic version" just
described. You have no way to change the length of the spring and
its' force once the part is made. So...

3a) CONTINUE this thread almost the entire way to the flare.
<other steps as above>
7) Make a thin threaded "adjustment ring" which fits over the outside
of the nut body and allows you to compress the spring more or less to
supply needed pressure for backlah comp.

Notes: You MAY need to reduce the diameter where the "fingers" begin,
so they have enough flexibility. This will depend somewhat on the
material chosen. Delrin works VERY well. phosphor bronze is also
typical.

If you're not up to the task of making an adjustment ring, you could
just use an appropriately sized(length) bushing with shim washers for
adding tension later...

If you use the same thread (extended) for the adjustment ring, you
will need to have a bottom to your mount threads. Two solutions: Make
another 'adjustment ring' and use it as a locknut. Or, add a setscrew
to the mounting surface which bears on the 'mount threads' of the
nut. Or (okay, at least 3!) use two different thread sizes.(mount
size will of necessity be smaller than the adjust threads).

Hope this helps. (and that it is clear)

Ballendo

P.S. You know, if you can get (or make) threads inside the collet,
you could even use an already manufactured collet! I'm thinking of
the soft types used for special sizes /shapes. Just have to thread
for the leadscrew and find (or make) an appropriate spring. BTW,
the "depth stop" threads in a 5C collet WILL NOT work since they do
not extend into the "finger" area...

> Apparently we see the construction of the part differently based on
> the description given.<snip>
> The split nut assembly will STILL be larger in diameter than the
> space I have available for it!
> Smoke