Re:- Ball Screw mounting block

>Mike Gann wrote:-
>
>I am gettig ready to install ballscrews on a
>small (and old) verticle knee mill. I am
>new to this and trying to figure out the details.
>I have attempted an ascii drawing below.
>
>Basically I will bore holes on each side
>into which angular contact bearings will
>fit. The screw goes through the bearings
>and the block and then a retaining nut is
>tightened on. Is this basically the way to
>do it?
>
>Also, is there any advantage to having this
>type of setup on each end of the X-Axis screw
>with a little tension applied to the screw, or just
>support the other end with a simple radial bearing.
>
>Any thoughts appreciated.
>
>Mike Gann

The usual way is two angular contact bearings back to back with a spacer in
between and two KM nuts that lock against each other.
KM nuts are those round ones that have 4 slots in them for a 'C' spanner.
Usually when these are initially assembled at the factory the inner sleeve
is ground to length to provide the correct pre load for the two bearings
used this means that the nuts can be tightened up tight as opposed to
trying to rely on locking one against the other and still maintain pre
load.

I have to change ball screws on some laser machines quite frequently.
Due to bad design these run in a trough at the bottom of the machine where
they collect all the cutting dust and oil from the screw and slides. This
makes a very good grinding paste. These screws are 3 metres long and last
about 6 months between re-con.
To ease fitting we have purposely ground the inner sleeve down by 1mm.
We then have a box of shims in various sizes so we can easily get the pre
load we need.

This week we scrapped a German CNC lathe to make way for the two new
millers I have bought. I saved the ball screws plus a few other bits.
Their method of mounting was to use a needle roller bearing in between two
flat needle roller thrust bearings, again with a pre - loaded sleeve.
--

Regards,
John Stevenson
Nottingham, England