Re: re:Final leadscrew design - thanks to all (not yet?!?!)Done

Ron,

That one will work. And the proportions are close. You could use
bolts and nuts to avoid any tapping(for the retainer plates)Good work!

Addt'l replies below

Ballendo

>The comments on the preload and the grinding of the bearing
>pair to a matched set was a little beyond me.

Preload is just a different way to say "less than zero clearance". So
you start with "slop, or play", and you reduce it until it is gone;
which is zero clearance. If you then reduce it some more, the parts
are pre-loaded.

The face grinding of the bearings is done by the manufacturer to
create this zero clearance or pre-load.

Let's pretend you wanted to do this yourself:

You take a plain bearing and the inner race moves(in relation to the
outer race) thrust-wise some amount; let's say it's .003 (pretty
typical for a small bearing)

Next you set some emery paper on plate glass and "face grind" .003
from the outer race of this bearing.
(The inner race will "float" since it can rise .003 working only
against gravity (mostly) and so will not be subject to much, if
any "grinding")

Can you see that while it is placed with the "ground" side down,
there will now be zero clearance?

But if you turn it over, it will still have the .003 movement?

Do this with two bearings, and put the "face ground" sides together,
and one bearing will keep the inner races from moving one direction,
and the "matched" 2nd bearing will prevent movement in the other
direction.

Now if we "grind" a little MORE... say .004 from each bearing
(we're assuming each bearing has .003 clearance(end-play).

We find that the bearings must be "squished" together for that
last .002 between them! THIS IS PRE-LOAD. Now we know that any force
LESS than what we used to "squish 'em together" will not cause any
thrust-wise(axial) movement!

>The final FIXED mount will require simple shimming under the lead
>nut, at most, to remove any play, per the Ballendo directions early

on, <snip>

Actually, the "shimming" will be BETWEEN the bearings (only for
the "cheap" plain bearings). What we're doing is realising that it is
easier to "take up the slop" with shims of the inner race, rather
than going through the "grinding" of the outer race described above.

Hope this helps.

Ballendo