Re: ATM Alternatives to Nylon-tipped screws

["Chuck Hards" <chuckh@companionsystems.com>]

Hi Don:

You wrote:

> The problem of Nylon screws loosening is news to me. I have found that
Nylon
> screws do not loosen. The threads deform and hold the screws in the same
way
> as the Nylon locknut works. Could the effect of loosening  have been due
to
> some other cause? Aluminum screws, unless hard anodized, will gall.

Yes, my experience with Nylon screws in some applications is that they
loosen with time, sometimes only a few minutes.  I first noticed it on a
Meade finder bracket.  The screws that hold the bracket to the doveltail
loosen quickly.  They are a 1/4-20 thread.  What appears to be happening is
that the portion between the threaded hole in the ring, and the finder
barrel, compresses.  The condition has nothing to do with the engaged
threads at all, but the exposed portion.

While I wouldn't hesitate to use a Nylon screw for say, a focuser, where you
only need it for a temporary grab, I've talked myself out of them for any
structural applications, including finder ring adjustment screws.  They
flow, or "creep" with time.  While not a problem with small finders, it is a
pain with heavier finders, and of course you can't use them for a guidescope
at all.

> A method of making for making plastic tipped metal adjustment screws that
I
(snip!)
> anaerobic blue or purple Loctite to the screw threads for that Nylon screw
> thread feel.

I've just tipped metal screws with a plastic tip myself.  Unfortuately, as
my eyes grow older, I've noticed that I tend to talk myself out of teeny
projects on the lathe because it's getting difficult to see the work.

Thanks for the note!

Chuck