re:Material to use for ballscrew mounting

Wally,

snips/answers below

>One of the things that has not been talked about is
>materials used for construction of the bearing mounts.

>1) I think an aluminum bearing block would be ok. But what about
>the end caps if using a rigid mount. Would the bearing faces press
>or work there way into the soft aluminum over time.

If the tolerances allow the movement, or "working" of the bearings,
THAT is your problem, not the material, IMO.

>2) If spacers are used in a rigid mount could they be aluminum or
>should they be steel.

Since we're dealing with thermal properties here, I'd use something
close to the material of the screw. So; steel.

>Also have a few general construction questions.

>1) If 2 angular contact bearings are used for rigid mount with
>spacers of the same dimension on both inner and outer races. Do you
>have to worry about preload or do you just tighten the nut on the
>leadscrew shaft a couple of grunts.

I like your "torque units" :-) . IF the spacers(relationship) size is
correct, then a "grunt" or two should not matter. Be aware of
the "grunt" ratio (housing grunts vs. leadscrew grunts).

>2) What about the bore diameter for you bearings. It seems you
>want the bearings to move as you tighten your end plate or if you
>add shims but you would not want the outer race to spin in it
>housing. What type of clearance/press fit should be used.

Light press fit. A little more than you can do by hand, but pretty
easily done with a small arbor press, IMO. You didn't mention this,
but same holds for the leadscrew diameter/bearing fit.

Hope this helps.

Ballendo