Re: [CAD_CAM_EDM_DRO] re:Re: leadscrew bearings / machine design(2nd gif dwg)

Good point Ron! I'd still only use one bearing tho'. If you replace (see method B) the two bearings and the spacer collar with an angular contact bearing and then place a spacer on the shaft oustide the bearing, the retainer nut can be drawn down tight making the bearing inner race immovable relative to the shaft. Since the actual construction of the lead/guide support plate isn't shown I could only suggest adjusting the axial end play using shims under one or both of the retention plates. Were I doing it myself, I'd build the guide support plate so as to adjust the end play by fitting the plate itself and eliminate the shims. This method would eliminate manufacturing a lot of parts and provide the most solid permanently adjusted assembly you could ask for.

If you have to work with an existing guide support plate, make an adapter (if there is enough room) shaped like a cup with a hole in it slightly smaller in diameter than the outer bearing race and a flange on top for bolting to the support plate. If there isn't enough room for that than both retainers could be made as "fit at assembly" items.

BTW....the description in paragraph one is essentially the way bearings in nearly all multi-spindle drill heads used in the automotive industry are mounted. I should know...I worked in that industry for years!

If anyone needs a sketch of this, post a message and I'll post a small file showing the details.

Smoke

-----Original Message-----
From: ballendo@... <ballendo@...>
To: CAD_CAM_EDM_DRO@egroups.com <CAD_CAM_EDM_DRO@egroups.com>
Date: Tuesday, October 24, 2000 9:10 PM
Subject: [CAD_CAM_EDM_DRO] re:Re: leadscrew bearings / machine design(2nd gif dwg)


Ron,

That helped. The part that is confusin' for us "been there's" is that
the scale of your drawing is "too tall, not wide enough"> If
you "squeeze" it from the top and bottom, while you "stretch" it from
left to right(until each "bearing" box is about square) you will be
closer to what the "typical" is.

So the bearings will look more like (angular contact on right):
_ _ _ __
|_|O|_| |_\O\_|

_ _ _ _
|_|O|_| |_/O/_|


Now that thats covered, lets see whatcha got:

Method A appears to be correct. As you (and I) mentioned, this one
can easily wreck bearings. But it IS used a LOT on lower end stuff.

Adding a spacer collar(simple cylinder, no step) between the bearings
(inner races) makes this a much better system! This is also the one
where the internal "step" can be a sleeve fastened into the straight
bore.


Method B appears to be close to what Jon E described.

(I believe he was detailing a method to use when you have a small
dia. screw, or don't want to machine the ends of the screws) In this
case, your spacer collar will actually fit OVER the end of the
UNMACHINED screw.
(like an old potentiometer shaft extension, for you radio guys :-))

The way you have drawn it(which will work): There is no need to
reduce the diameter of the leadscrew for your "spacer collar" to have
a step. Again a simple cylinder spacer will suffice.

You didn't draw the one I spent a thousand words describing? :-)
Functionally, it will be like method B. But MUCH stronger, unless
the "cover" Plates are "real thick".

If you look at method B and assume one of the housing cover plates is
just part of the housing, and the other cover plate is the camera-
lens nut, you'll have it, I think.

Remember, both of these would be considered "rigid" mounts, since the
bearings are spaced. Method B really needs a spacer between the outer
races of the bearings. To be REALLY rigid, that is; it WILL work as
drawn.

Hope this helps.

Ballendo


P.S. I just searched online for a link (or links) to post for this
thread. Came up empty!(was very surprised) All the major
manufacturers DO indeed show only the screw stack or "cartoons".
Several years ago this was not the case! I wonder if too many people
were makin' their own? :-)

Another thing I noticed during the search is that most mfr's were
showing fixed instead of rigid. Maybe just because the block (and
materials) cost less; maybe bearings are better??

Anyone else find a link to post showing the three std. end mounts?


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