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

Ballendo,

Excellent, thanks for spoon feeding me. Thats exactly what I
needed. Nicely explained.

Ron

--- In CAD_CAM_EDM_DRO@egroups.com, ballendo@y... wrote:
> 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