Re: Ballscrew Nut-blocks and Thrust bearings

PTENGIN@... wrote:

> Another possibility is to use Timken taper roller bearings. I was
> supprised to find they come as small as 10 mm bores. Approx .3937". They will
> hold up to thrust much better. I'm using thrust type ball bearings but am not
> completely happy because they are difficult if not impossible to get with
> shields or seals.
> One note on using two nuts on an axis for preload. I bit the bullet

I designed and built ballscrew end bearings similar to the Thomson units
to save the $2400 or so to just buy them. They use two 40 degree angular
contact bearings in the DB preload configuration. The cost for steel,
bearings and seals was about $40 per unit. I have a poorly drawn autocad
design file for 17 mm bore units that I would be willing to e-mail to
anyone who needs it. Much machining work to .0002" tolerances is
required.

I ended up with Hiwin ballscrews. The 25 mm units are sold as a single
2.5 meter length with two oversize ball 5% preloaded nuts. List price
for these are $320 for the .002"/ft lead accuracy C7 grade. Normally
these are cut to make two 1.25 meter units each with one preloaded
flanged nut.They look ok but end machining service is not available so I
spent the weekend at the lathe. The RC 55-60 casehardened screws can be
machined without annealing with carbide tooling. The core is about
RC 40.

I was told by a Saganaw engineer to not flatten the wave washer also.
But for my large machine the preload is just not enough hence the
oversize ball method.

Leslie M. Watts
ITW Advanced Technology Group
(847)657-4559
http://www.netcom.com/~leswatts/leswp.html