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

Thanks...I'll give this one a bit more thought...when I get a round
tuit....I have an idea that MIGHT improve yours a bit.

Smoke

>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
>
>
>
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