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  • SB 13 cross slide

    I'm installing an NOS cross slide lead screw assembly on my South Bend 13 and although it turns freely off the machine, when it's installed it will only make 4-1/4 turns before it stops. It looks like the gear that turns the power cross slide is responsible but I tried moving the levers and that doesn't help.

    I'm new to this machine and I've never had a lathe with power cross slide. Prior to this I had a 9C.

  • #2
    This is the sort of thing that's very tough to diagnose over the interwebz. For example, is it a hard stop or more of a building resistance to a full bind? And so many other possible questions.

    So all I can offer is to check the basics. Set up the screw in some V blocks or between centers on the lathe and start by making sure it hasn't gotten bent at some point. Other than that I'd suggest marking the parts with felt marker, assemble and turn things until they bind then break it down and check the felt marker for scuffs that shouldn't be there. Assume that nothing is straight and check everything with dial gauges, straight edges or other suitable methods which don't rely on the questionable accuracy of the ol' MkI eyeball in its natural unaided state.
    Chilliwack BC, Canada

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    • #3
      It's a hard stop and the lead screw is dead straight. It turns fine until the outer part is screwed in far enough for the gear to engage.

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      • #4
        My guess would be that it is in the gear train in the apron. Make sure that the feed levers are set in the right position. If the feed is set for cross feed and the clutch is engaged you will not be able to turn the screw. Set it to longitudinal feed and disengage the clutch.

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        • #5
          Originally posted by Commander_Chaos View Post
          It's a hard stop and the lead screw is dead straight. It turns fine until the outer part is screwed in far enough for the gear to engage.
          This seems an odd description.

          The drive gear should always be engaged with the feedscrew gear. There is a clutch that engages the drive train with the crossfeed, AND it is on most SB (IIRC) engaged with a screw-down knob.

          It sounds as if the feedscrew is backdriving the clutch through the feedscrew gear and causing it to engage. You may have to dig into the clutch and apron, something may be stuck with old congealed gooey oil.

          The clutch SHOULD be free to turn via the crossfeed unless the clutch is engaged using the knob on the apron. Check the knob... it also could be engaged. I don't know if there is anything that can backdrive that way if the clutch was partly engaged..
          CNC machines only go through the motions.

          Ideas expressed may be mine, or from anyone else in the universe.
          Not responsible for clerical errors. Or those made by lay people either.
          Number formats and units may be chosen at random depending on what day it is.
          I reserve the right to use a number system with any integer base without prior notice.
          Generalizations are understood to be "often" true, but not true in every case.

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          • #6
            Have you rigged it up with everything except the actual cross slide? The mechanism is all in the apron and saddle so you should be able to confirm everything rotates correctly. Then fit the nut without the slide and just hold it and see it go up and down correctly.

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            • #7
              Originally posted by Commander_Chaos View Post
              It's a hard stop and the lead screw is dead straight. It turns fine until the outer part is screwed in far enough for the gear to engage.
              Here, I'm assuming that you are actually assembling the screw into the cross-slide. It sounds like your clutch is engaged, or the gear train is seized up. The feed on a SB13 is much different than that of a 9C. The 9C uses the half-nuts to drive the carriage. On the 13", the half-nuts are used ONLY for threading. The feeds on the 13" are selected by engaging the correct selector position on the apron, then tightening the clutch. If the clutch is tight, it is "in gear". If the clutch is loose, then the gears should free-wheel.

              QUESTION: Does the longitudinal feeding work (using the above info on how to engage it)?

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              • #8
                The longitudinal feed is fine. I took the saddle off and peered down into the apron and there were no glaringly obvious problems. I reassembled it and now the hard stop is a soft hangup every four or five turns. I'm thinking now that the clutch is toast. In any case I have one small job to take care of this weekend and then I'll tear the apron down for a refurbishment.

                When I mentioned the gear not engaging, what I meant was when the stationary side of the dial is threaded a couple of turns into the saddle, the handle turns freely. When it's threaded in far enough to engage the gear, there's problems.

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                • #9
                  If you are going to tear into the apron I would advise you to get the manual;

                  Rebuild Manual for South Bend Lathe 10L, 10R, 13, 14.5 & 16 | eBay

                  or even better the rebuild kit:

                  South Bend Lathe 13" - Rebuild Manual and Parts Kit (All Models) | eBay

                  It is a complicated assembly. The alternative is to look for one of the YouTube series on the rebuild. I went through mine about a year ago and I am glad that I had the manual.

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                  • #10
                    Was the cross feed working before you changed the screw?

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                    • #11
                      I hadn't tried the cross feed. As soon as I had the machine going I jumped right into making stuff and my old lathe was manual cross feed so I didn't even think about it. With the lead screw out I could see the gear turning but with it together it didn't move.

                      I wouldn't tear that apart without the manual. I'll watch the videos, too. Regardless of what's wrong in there it's overdue for a cleaning.

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