Re: [CAD_CAM_EDM_DRO] Re:- Ball Screw mounting block

How is the pre-load determined?
Is this based on a spec from the bearing?

Thanks for your input.

Mike Gann

John Stevenson wrote:

>
>
> >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
>
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