RE: [CAD_CAM_EDM_DRO] re:Moglice Problem - Fixed?

>-----Original Message-----
>From: ballendo@... [mailto:ballendo@...]
>>Cast the epoxy nut on the most worn section of your screw, but only
>>cast HALF at a time.<snip>
>
>You will want to cast over the BEST part of your screw! picture a
>worst case where the screw is worn to only 1/2 thread height:
>
> | |
> __ | __ __ |
> /__\ __ Where the threads are OK |__// \\__// \\__|
> / \__/ \__ the nut will fit like: / \__/ \
>

This assumes that the wear happens only on the crown of the thread. Actually,
almost *no* wear occurs there. Almost all of the wear in on either cheek of the
thread, so the ASCII art should look like:
Worn thread new thread
__ __ ____ ____
/..\ /..\ /....\ /....\
___/....\______/....\___ __/......\____/......\____
........................ ..........................

Nut cast on worn running on new Nut cast on new running on worn
IIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIII
IIII/__\IIIIIIII/__\IIII III/ \ \IIIIII/ \ \IIIII
III/....\IIIIII/....\III II/ \_\IIII/ \_\IIII
__/......\____/......\__ ..........................
........................

Note that in the right drawing, the nut has longitudinal play equal to the wear
on the thread, which is what this whole exercise is trying to avoid.
In the left drawing, the nut has no play, but has expanded a bit to fit over the
wider threads.
The same holds for standard (non-Acme) threads.

The real problem with casting on the worn area is that you *must* split the cast
nut in situ; until it is split, it won't screw off either (unworn) end of the
screw! On the other hand, that may be the best way to actually split it: Cut
longitudinal groove as deep as you dare, then start unscrewing it.

To make an expanding nut like this really work properly, it should be split into
4. If it is only split in 2, the halves must separate much more to provide extra
clearance near the split line (where the "splitting" motion is tangential, not
radial, to the screw). If you want to get fancy you can split it collet-style: 8
splits, each one 3/4 of the length, alternating from either end of the nut!
-Kevin Martin