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Adding a gearbox to a SB 9" lathe......

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  • Adding a gearbox to a SB 9" lathe......

    I have a Southbend 9" lathe with a 54" bed that did not come with a gearbox. I have since bought two gearboxes and one came with the leadscrew, gearbox, sector bracket/gears but it is for a shorter bed than what I have. Is it feasible to cut the two leadscrews and make one? How much stress is placed on the leadscrew when the gearbox is operating? Thanks, emj.

  • #2
    Add an extension to the short lead screw. I doubt very little work is ever done with the average user on the far right end of the bed.

    JRW

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    • #3
      Is it possible to modify the non-QC leadscrew? That would be my first choice.

      If not, I have seen writeups on splicing leadscrews by turning a reduced diameter spigot on one piece to fit a bored hole in the other and silver soldering them together. Care should be taken to maintain concentricity and matching the threads of course.

      I would make the joint about 1" long.
      Jim H.

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      • #4
        I've used the method JC mentions. Works well on shafting as long as spigot OD and bore ID are close -- size-on-size preferably. Never tried this with an Acme thread like the SB leadscrew but it should work well.
        Barry Milton

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        • #5
          I would just order a length of new precision acme rod (MSC carries it), and turn it to fit the gearbox and end bearing.

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          • #6
            if your model c came with a leadscrew, your better off using it. you will have to cut the left end off to fit to the gearbox and cut a keyway the length of the acme thread, this cost me $35.00 at a local machine shop. good luck

            [This message has been edited by rick peer (edited 03-21-2005).]
            rick

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            • #7




              [This message has been edited by emj (edited 03-21-2005).]

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              • #8
                <font face="Verdana, Arial" size="2">Originally posted by J. R. Williams:
                Add an extension to the short lead screw. I doubt very little work is ever done with the average user on the far right end of the bed.

                JRW
                </font>

                I never thought of that. Thanks,emj.

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                • #9
                  <font face="Verdana, Arial" size="2">Originally posted by rick peer:
                  if your model c came with a leadscrew, your better off using it. you will have to cut the left end off to fit to the gearbox and cut a keyway the length of the acme thread, this cost me $35.00 at a local machine shop. good luck

                  [This message has been edited by rick peer (edited 03-21-2005).]
                  </font>

                  I was kind of thinking of doing this also. I may try adding an extension on the leadscrew that came with one of the gearboxes as mentioned by JRW and see how well it works. Thanks,emj.

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                  • #10
                    <font face="Verdana, Arial" size="2">Originally posted by JCHannum:
                    Is it possible to modify the non-QC leadscrew? That would be my first choice.

                    If not, I have seen writeups on splicing leadscrews by turning a reduced diameter spigot on one piece to fit a bored hole in the other and silver soldering them together. Care should be taken to maintain concentricity and matching the threads of course.

                    I would make the joint about 1" long.
                    </font>
                    Another option to consider. Thanks, emj.

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                    • #11
                      I would be concerned about accuracy in splicing the leadscrew together. It is going to be hard to synchronize the two threads. What you will have is a jump in threads at that point, likely worse than any wear that might be found on a well used screw.

                      I would either construct another one from precision acme rod or look for the correct one on E-Bay or other used sources. Sadly, many SBs are parted out.

                      Paul A.
                      Paul A.
                      SE Texas

                      Make it fit.
                      You can't win and there is a penalty for trying!

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                      • #12
                        <font face="Verdana, Arial" size="2">Originally posted by Paul Alciatore:
                        I would be concerned about accuracy in splicing the leadscrew together. It is going to be hard to synchronize the two threads. What you will have is a jump in threads at that point, likely worse than any wear that might be found on a well used screw.

                        I would either construct another one from precision acme rod or look for the correct one on E-Bay or other used sources. Sadly, many SBs are parted out.

                        Paul A.
                        </font>

                        The added extension will be at the rear of the leadscrew where there are no threads. If I cut/splice the front of the leadscrews together, it would be just after the front leadscrew support. There is a large diameter journal located just past the support. Or machine the leadscrew off my 54" bed SB to match the shorter leadscrew that came with one of the gearboxes. I have a few more options then I originally thought I had. Thanks, emj.

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                        • #13
                          What I want to know is what are you going to do with the extra gearbox?
                          David from jax

                          ------------------
                          Have gun, will travel.
                          A serious accident is one that money can't fix.

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