[R-390] R-391 positioning head

[Bill Hawkins]

Barry Hauser said,

"I think there are all sizes of these bearing
 available, but might be tricky to press them out and new ones in.
 I wouldn't want to hit that casting with anything too hard."

Yes, the bearings have to be pressed out and new ones pressed in.
That last sentence should read, "I wouldn't want to hit that
casting with anything!" A pretty good press can be cobbled up
if you've got a bench vise and some round and flat bar stock.
You'll need a micrometer to get the right diameter for new
bearings. Use a hammer and you will cock the bearing going in
or scratch the housing bore going out.

If the bearings are just dry and not worn, you can cobble up
a "recharger" for sintered bronze bearings. Take the shaft out
of the bearing and immerse the bearing and housing into a small
jar or can of light oil. Now comes the tricky part. Pull a
vacuum on the contents of the jar, perhaps using a vacuum hose
from the carburetor of a running engine. Try not to suck oil
into the engine, lest bad things happen to expensive machinery.
If you can see the bearing, you'll see air come out of it. Wait
for it to stop bubbling, then break the vacuum slowly. Oil will
run into the pores in the bronze. Works better if oil and bearing
are warm to hot. Good idea to test your vacuum chamber first, lest
you get hot oil and broken glass all over everything.

We made sintered bronze bearings from bronze powder in shop class,
and oiled them using vacuum after they'd cooled from sintering.
Great stuff. But that was the fifties - too dangerous now.

Disclaimer: Forget everything I just said. If you don't have
a bearing press and micrometer, take it to a pro. They may still
make bearings, but they don't make housings anymore.

Regards,
Bill Hawkins