Re: [CAD_CAM_EDM_DRO] Plastic leadscrew nuts

In a message dated 19-May-02 08:00:52 Central Daylight Time,
zvon@... writes:

> Some time ago there was an interesting thread regarding the leadscrew
> nuts moulded from Moglice. The nuts showed a minimal or no backlash
> initailly.
>
> Is there any information available in regard to their wear after a
> period in service.
>
>

Zvon: I know nothing of this Moglice. I know only of "Turcite" which is a
fiber-glass-impregnated PTFE plastic that BSA uses. It is
"self-lubricative", yet quite tough. It does NOT have any particular
low-backlash itself, but IS made/sold in preloaded configuration, with a
spring between two "keyed" halves. This is effective, at least for plotters
and wood-working devices. Me, I would shy away from using it on metalworking
devices like lathes or milling-machines.

I have used this on several of my home-brew machines, and have noted on thing
on one machine that has run, now, for eight years: The fiberglass in the
plastic seems to work like a polishing-compound, and there is NOTABLE wear on
the area of the lead-screw that "sees" the nut most of the time! That area
of the screw is wonderfully polished, and I took the red plastic nut OFF the
longitudinal screw, once, and the threads are PACKED with black swarf! I
cleaned this out with a "tap" made from a scrap of the same ACME screw, and
all was good again. But the nut is "free" only in that "often-used" region!
It tightens right up when moved to a "fresh" area on the screw! Hmmm.... !
! ! ! ! ! !

Jan Rowland


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