Material to use for ballscrew mounting

I have been following this ballscrew thread closely and have learned
quite a bit. One of the things that has not been talked about is
materials used for construction of the bearing mounts. My questions
come from the standpoint of a bridgeport retrofit.

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

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


Also have a few general construction questions.

1) If 2 angular contact bearings are used for ridged 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.

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.

Wally K.