Re: rolled ball screws

I have read some reports on the kind of
oversizing, I guess some MFG's are evaluating
this methode too, they are experimenting with
different Nuthousing designs that would allow
them to expand under the pressure of oversized balls.
Probably gone be a while before they offically
give there blessing to this methode.
It seams that some people have gotten there Ballnuts
fitted by employees of those companys unoffically.
Gotto now somebody that nows somebody that has a
cousin kinda thing.
I like the Idea more and more as I think about it,
The problem Is the pitch variation of the screw, so
shorter Nuts = less of a problem right.
If the main concern is Backlash and a bit of a rougher
ride and shorter life expectancy can be tolerated then
this would not only be the cheapest but also the most
effective solution.

Now if we could just get the Mfg's to do the preloading
things would be peachy.
I would not like to order 200 little balls to do this myself
just to find out that they are still not big enough.
I also heard of people using different size balls in alteration
I guess they just could not get enough of the right size.
This would probably not be such a good Idea, because I think
this would reduce the load rating by half, or not?
You mentioned some about Nuts "work in", are you speaking of
experience with them.
Because I don't think they are suppost to do that, hard steel
components usually work as designed without much variation
during there life expectancy and then fail rapidly.
But I agree that breaking them in may be a cautious approch.

Thanks a lot everybody your input has helped a lot.


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ballendo <ballendo@y...>"
<ballendo@y...> wrote:

> Greg,
>
> The bottom-er line is that if you have a non-compliant spacer

between

> two nuts on a rolled ballscrew, you will then USE the yield value

of

> the bearings and races themselves to accomodate the inherent lead
> innaccuracies.
>
> Which is a BAD thing! VASTLY reduced life, uneven motion (or even
> locking up), and possible catastrophic failure are all possible
> consequences...
>
> What CAN work with rolled thread, is to slightly oversize the

balls.

> Dan Mauch first made me aware of the possibility, and it works.
> Single nut (cheap), oversize balls (cheap,but hard to find), and

time

> spent reloading, and you've got a solution.
>
> If the balls are TOO oversize, you're right back where i started
> above. But if you get the size right, and let themn "work in" a bit
> before asking for full load and quick traverse; the slight

burnishing

> of the rolled thread and nut actually helps seat the two parts
> together. Shorter nuts are better for this technique, which means

it

> is not suited to high loads. Dan and I used it in mill/drills,where
> it works well.
>
> Hope this helps,
>
> Ballendo
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Greg Jackson" <greg@t...>
> wrote:
>
> <snip>
> > Bottom line is that a stiff system between the nuts allows for
> longer life
> > on the ballscrew without the risk of the working load overcoming
> the nut
> > preload system.
> >
> > Greg
> >