[pstockley]

I have the opportunity to pick up some really fancy super precision ballscrew bearings that normally cost around $800, for peanuts. The problem is that they are 25mm ID. The ballscrew I will be using has a 20mm diameter. Is it feasible to fit a ground spacer with a shoulder? If so where can I get one from?

[NC Cams]

Yes, it is feasible to make and grind a shouldered spacer/bushing.

You can start by scrounging up a tapered roller cone with the ID you want, fit it to an arbor and grind the OD to suit your needs - ditto that with the flange.

You can also take some of the money you saved with your score and have one precision made by a good grinding house.

Try KAF Mfg in Stamford Ct to have one made but they will NOT be cheap but it WILL be jewelry...

[pstockley]

They are new still sealed and only cost $50 so its definately worth it. I will see if I can find someone locally to grind up a spacer.

[NC Cams]

Shoot for a SFNS (slip fit, no slop), ID of bushing to shaft as well as OD of bushing to ID of bearings.

The radial runout shouldn't be an issue as that will be pretty easy to deal with when they OD grind it to size.

The axial runout is what you want to minimize for ball screw work. A person who does reasonable OD grinding should be able to axially "bump" grind the flange when they do the OD grinding work for you. Face runout of the bumped surface should be under a half thou or less....

We do bump grinding of cam sprocket mounting faces all the time when we tune-up grind the faces of billet cams - should take 15-20 mins, half hour tops - to bump the flange, both sides,

I"d figure an hour all totaled assuming the ID was properly reamed for a slip onto the grinding arbor shaft OD.

Although the material would not have to be hardened, a hardened piece of steel would just be more stable.... Flame hardened, quenched and tempered 1050 or so would be more than adequate. Tool steel (IE drill rod)would be overkill....

The above "specs" should do you just fine....