Re: Bearing question for ballscrew conversion

Hi,

Jon E and Les W already said most of what I agree with.

The reason to use fixed-fixed (angular contact pairs at both ends)
instead of fixed-simple (what you have drawn) is to provide more
support for the rotating leadscrew, which allows smaller diameter
screw(s) and/or longer "spans" between supports(given a particular
l/s rpm).

To increase rigidity even further, a RIGID mount is used. This uses a
spacer BETWEEN each pair of angular contact bearings. Shims are
usually used for "fine tuning" this type of setup.

A properly designed fixed-fixed (or rigid-fixed; or rigid-rigid)
setup is NOT over-constrained. Either the temperature is controlled
(as Les mentioned), OR the second set of angular contact bearings are
allowed movement in an AXIAL direction.This allows for the expansion
of the shaft length, while still controlling "whip" of the rotating
leadscrew. You see this in grinding spindles also; where high speed
an the need for a fixed end point lead to the same sort of bearing
choices.

Hope this helps.

Ballendo

P.S. The "regular single bearing" is called a simple mount. Usually
this is a radial ball bearing.

--- In CAD_CAM_EDM_DRO@y..., cadman@p... wrote:
> As I layout my design for the ballscrew conversion, I'm wondering
if I
> need "Angular Contact" bearings at both ends. I'm thinking that
only
> one end needs to have two angular contact bearing with a clinch
nut.
> The other end can have a regular "single" bearing and let the lead
> screw "float" here.
>
> What does the group think about this? I have a crude ASCII art
> picture below.