Re: [CAD_CAM_EDM_DRO] mounting ballscrews onthe ol mini mill help

Hi All:
You can also split up the functions of the bearings by using radial
bearings and putting separate ball thrust washers on the ends.
It can be a bit screwy trying to figure out how to accommodate the extra
bearings, but it's a method I've used with success on other kinds of
applications where I needed good thrust capacity and couldn't get what I
needed in a single bearing.
In this application, an argument could be made that thrust capacity is more
important than precise radial running.
The argument goes like this: so what if the screw flops around a bit
radially...we care most about about eliminating backlash in the drive;
that's why we went to all the trouble to get ballscrews.
If the screw is free to flop around radially, it can self-adjust for
misalignment between motor, screw, and nut.

So....is this argument bullshit???: or does it have some merit???
I await enlightened responses.

Cheers

Marcus

----- Original Message -----
From: "Les Watts" <leswatts@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, October 02, 2002 5:49 AM
Subject: Re: [CAD_CAM_EDM_DRO] mounting ballscrews onthe ol mini mill help


> Well, there isn't going to be much compression load on a 3/8"
> screw.... it would buckle unless it was very very short.
>
> I think you could get away with regular conrad type ball bearings
> if you deal with the axial clearance. Note that on these bearings
> the inner race can move around axially quite a bit. This would cause
> massive backlash. But you can use pairs preloaded
> against each other. That really turns them into angular contact
> bearings with a few degrees contact angle. They are spaced
> with an inner and outer sleeve of slightly different lengths.
> Do this on one end only.
>
> Ordinary deep groove ball bearings are rated for light thrust loads-
> all bets are off if you get shock loads from a crash or something
> though. But hey- these are $3 bearings.
>
> You can get single and double row angular contact and tapered
> roller bearings easily at places like MSC, Grainger, and Reid
> if you want. They can cost much more and yes might be hard to find in
> such a small size.
>
> Les
>
> Leslie Watts
> L M Watts Furniture
> Tiger, Georgia USA