Re: [CAD_CAM_EDM_DRO] Angular Contact Bearings and Ballscrews question

kaynrc wrote:

> Hello
>
> I am starting to look for angular contact bearings to intsall in one
> end of the leadscrews for a mill. I seem to recall that the screw is
> firmly held at one end, while it can "float" in the other end,
> meaning that with expansion due to temperature, one end of the
> leadscrews sit in a radial bearing.
>
> So, are there such beasts as double angular contact bearings?

There are pre-fitted sets of these, supplied with spacers to set the preload.
You need a bearing nest to hold both bearings, and some sort of threaded
clamp to constrain the inner races against the spacer.

> Or is
> it common practice to buy 2 for each screw, and mount them backwards
> to take up thrust forces in both directions?

Yes, this is probably cheaper, and more easily available off the shelf at the
bearing distributor. You make a two-sided bearing nest, with a step between
the two bearings to hold the outer races apart. You machine a step down
on the end of the ballscrew, and thread the smaller end for a collar that
clamps the inner races toward each other.

> If they are sold in
> double row, do they make them small enough for a .631 screw, with a
> base diameter of about 0.500"?

I imagine you could find such a single bearing, at least, in that size, but the
axial load rating may be limited. There is no such thing as a double-row
angular contact bearing, as far as I know, because there would be no way
to assemble it.

> Would tapered roller bearings work just as well? Or are they too long
> and bulky or something?

This would certainly work, but you may not find them in this small size.
They would have more friction than a ball-type bearing. No problem with
the axial load, though.

Jon