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[atlas_craftsman] Some parts recently replaced

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  • John D.L. Johnson
    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
    Message 1 of 2 , Jan 6, 1999
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      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
      jjohnson@...



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    • Harry Wade
      ... John, This is not likely, you would have seen smoke. However the potmetal, which is actually Zamak (zinc-aluminum) does scar or gall easily, and I have
      Message 2 of 2 , Jan 6, 1999
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        At 09:02 PM 1/6/99 -0800, you wrote:
        >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. (snip)
        >John D.L. Johnson


        John,
        This is not likely, you would have seen smoke. However the potmetal,
        which is actually Zamak (zinc-aluminum) does scar or gall easily, and I
        have seen any number of die cast Zamak parts (not necessarily Atlas) which
        were mal-formed or incomplete due to cold flow in the mold. A combination
        of these two could make them appear as though they were melted.

        Regards,
        Harry Wade
        10 x 36 and 6 x 18


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