When I purchased my 12"x36" Craftsman M/N 101.28990 (circa. 1975) last year,
I knew I would have to replace some parts. So far not too much. I found
the Carriage Slide Nut P/N 537-041 was very worn, so I ordered one from
Clausing for $40.00. The next parts I decided to make myself.
One day I started hearing some squeaking from the change gears, so I did
some investigating and found that some time before I purchased the lathe,
both Change Gear Bushings P/N 9-70 had run dry and the inside surface was
all scared up. These are pot metal parts that turn around a steel Sleeve
P/N 9-73A. Apparently they must have gotten hot enough to melt the inside
surface and the metal then re-hardened in a funny pattern. I also noticed
that the Change Gears which these Bushings turn seemed to be rather loose on
the Bushing. So I decided to make replacements for both with bronze. Here
is how I did it.
I started with solid 3/4" Bronze bearing stock. I turned this own to a
close fit with the inside diameter of the Change Gears about 0.755". Each
part is 1" long, so I made the two together. Then I center drilled the
2.250" bar and bored out the center to fit the Sleeves at about 0.500".
OK, so far that was easy. Now to make the two wings that fit into the
Change Gear keyway notches. I then milled a 3/16" keyway slot on opposite
sides of the bushing stock 3/32" deep on the milling attachment. Then from
some flat 1/4" Brass bar stock I machined two 3/16" key stock about 1/4"
high and 2.250" long. Now to cut the bushing in half and down to two 1"
pieces. This was done on the 4-jaw with a parting tool first and then just
faced off to 1" long. The key stock was then cut into four pieces and
silver soldered into place. On one piece I must have heated it up too high
and got some deformation on the internal diameter. This was cleaned up with
another light pass with the boring bar. Then back in the 4-jaw to bring the
keys down to 1" length with the rest of the bushing. Now the keys stuck out
too far to fit into the key ways on the gears, so back in the milling
attachment for milling down to the right height to fit. And that was that.
Now, since I still needed the power feed on both the lathe and milling
attachment, I had to disassemble and reassemble each time I needed to check
fit, so that was a pain, but with patience, I got the job done. Now I have
bushings that will last, with a little oil, for 50 years!
John D.L. Johnson
California State University, Chico
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