Hoyt McKagen <batwings@i-plus.net> wrote

> Would aluminum for the support blocks be an absoultely hidious idea?

Nope, it's pretty good choice. Thermal expansion isn't going to be a
problem and it's easy to shape. I used it in mine and they work fine.

> How tight a press fit should it be to get the bearings into the support
> housing?

You should use a slip fit or at tightest you might need to heat the
housing and push hard by hand. Mine are slip fits, no problems.

> To preload the angular contact bearings, what can I use as a spacer between
> the inside races?

I used paper of varying thickness including cigarette papers that may be
thin as .0005-.001"

I was playing with aluminum foil and found that about 12
> layers made it so I could still squeeze the outside races to touch. Should
> the outside races be able to touch?

Yes, the total pack thickness should barely take up the play in the
bearings, then you add one smidgeon to get the actual load.

>How much preload is too much and how do
> I measure it? Would layers of aluminum foil be ok for the spacers?

The foil is fine and gives you very small increments. If you can install
it in good shape (delciate bits, no?) it will be perfect.

To decide how much, set up your ball screw and bearings in the housing
and fasten the retainer on. Then measure axial play. The shim pack should
be exactly that amount to get line to line action. You may have to make
two trials to make sure you've pickd up all the play. Once you've got
play out, you can increase the preload one shim and feel the turning
torque on screw. IGWS that you do not want them to feel notchy or rough
or make creaking noises.
>
> What can I use for the bellows to cover the ball screw and insure it doesn't
> wear out prematurely due to grit and swarf?

Make cover that fits above them. On mine the ball-nut carrier goosenecks
down and then turns back up, to fit under a long piece of channel. The
gooseneck is made by bending a piece of 1/2" plate 90 deg at end. Then
this is slit through so the cover will pass above and to each side of the
portion carrying the nut. Nut itself goes into a holder that fastens to
the gooseneck on a single stub with threads and a ring nut. If you like
I'll take some snaps and copy you.

Regards,

Hoyt McKagen

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