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  • Southbend spindle question.

    My mate bought a old southbend lathe. It looks to have sat unused for a long time. I dont think its bigger than a nine. These are not that common in Africa as we have chinese lathes. I breifly looked at it and two things concern me. There was some shim stuck under the flat of the tailstock. The tailstock has quite a bad ridge on both edges . My nail tells me about .3mm . The next big mood killer is that I can feel end float and radial play on the spindle,maybe as much as .3mm as well. The biggest concern is the spindle gear where the drive train joins on is damaged.

    Is there a way to rebuild this up. We cant do the e bay thing here .I am wondering if it could be machined off and a new gear silver soldered on, or would the spindle warp with the heat. Could it be locktited on. This lathe looks different to the ones in pics. Instead of a flat pully cone it seems to have v pulleys.

  • #2
    Most common method is to build up the gear with brass braze and file it to shape... It's a common problem. V groove pulleys mean that it is a newer model (after WW2). If I remember correctly, the gears are 14.5* pressure angle, pitch is either 16 or 20 diametral pitch. Shouldn't be any big problems with warping or distorting the spindle if you use ordinary caution.

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    • #3
      It sounds to me like the tailstock may have come from a different lathe and the shims were needed to bring it up to the level of the headstock. Just verify it's alignment and run with it.

      0.3mm (0.012") radial and axial play in the headstock sounds excessive. I fear that it may be beyond adjustment.

      I am assuming the journal bearing design, which is what my SB-9 has.

      For the axial play, there should be a nut that takes up that slack. Try to locate it and adjust it as needed.

      For the radial play, there should be some shims in the gap between the headstock. You may be able to adjust this play by removing some or all of them. But 0.3mm is a lot: it suggests excessive wear.
      Paul A.
      SE Texas

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

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      • #4
        Originally posted by Paul Alciatore View Post

        For the radial play, there should be some shims in the gap between the headstock. You may be able to adjust this play by removing some or all of them. But 0.3mm is a lot: it suggests excessive wear.
        I wonder if its possible to open up the gap where the shims go? So that you can pinch the adjustment tighter. And use *plenty* of oil on the spindle...
        Last edited by nickel-city-fab; 08-10-2019, 04:47 PM.

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        • #5
          Are you sure the damaged gear is part of the spindle and can't be removed? With the other issues you have with slack could be a good time to strip the spindle out, clean/repair things, and put it back together adjusted properly.
          'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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          • #6
            The SB9 uses a sintered bronze bearing for the main bearing. And as mentioned it is adjustable. But such bearings are not adjustable over a wide range since that would affect the alignment of the main shaft to the bed and produce odd turnings if this is not kept to within a fine degree of parallelism. So any adjustment or repair needs to be done with the need to measure the spindle for parallelism to the bed at the same time.

            There's OODLES of good videos on stripping down and rebuilding SB9 lathes of all ages. I'd start with that and with identifiying just which South Bend he has from sources such as the South Bend small lathe page at lathes.co.uk

            http://www.lathes.co.uk/southbend9-inch/

            Sadly it sort of sounds like the lathe was run without a lot of thought about the need for proper lubrication. If that is the case and the bearing journals and bearings are badly galled and worn then fairly extreme measures are likely to be needed to get the lathe back up and in operation.

            But any such evaluation must start with a full detailed strip down so each part can be evaluated for condition and options if damage is seen.
            Chilliwack BC, Canada

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            • #7
              I will have a closer look when he has taken the centuries of grease off it. There are alot of videos but strangley I could not find a video of the repair of the gear on the spindle. I wonder if it would not be possible to make a loose gear that keys onto the spindle and change the size of the tumbler gears to allow the gear train to fit. Then there would be no welding or gear cutting involved. Those are two skills I dont possess.
              Apparently its a 1941 model.
              Last edited by plunger; 08-11-2019, 03:15 AM.

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              • #8
                The South Bend 9 that I had, had the spindle gear machined into the spindle. I had to replace the spindle on mine due to wear in the spindle gear. As for the spindle bearings, the spindle rides on oil in the head stock. The head stock is the bearing. Mine had segmented bearings, no bronze, cast into the head stock. Mine was born in 1946 earlier ones did not have segments. The head stock caps were shimmed to get the proper oil clearance for the spindle. I don't remember exactly but may be .0007'' clearance.

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                • #9
                  Originally posted by plunger View Post
                  I will have a closer look when he has taken the centuries of grease off it. There are alot of videos but strangley I could not find a video of the repair of the gear on the spindle. I wonder if it would not be possible to make a loose gear that keys onto the spindle and change the size of the tumbler gears to allow the gear train to fit. Then there would be no welding or gear cutting involved. Those are two skills I dont possess.
                  Apparently its a 1941 model.
                  Plunger, there may not be a video on fixing a gear on specifically a South Bend but there are lots of videos on YT on repairing broken gear teeth. Try the search terms "replacing broken gear tooth" and "repairing broken gear tooth".

                  One of the lower tech repairs that deals with a lathe's back gear setup also includes a peek at a single tooth shop ground flycutter for the cutting of the tooth. For a one time repair we do not need a whole set of gear cutting wheels.

                  https://www.youtube.com/watch?v=n5S-5B7jomU

                  But wait.... order now and you'll also get.....OK, I can't find it now but there was a video on repairing broken gear teeth on larger sized gears such as we have on our lathes where the guy brazed in a new tooth then carefully cut into the blob of brazing with a hacksaw and then filed it to shape. That's right, hand filed it. And while it didn't show him doing so I'm going to assume that this was done in concert with meshing the tooth/teeth being shaped with another gear and looking at and touching up any shiny spots until a good mesh was achieved.

                  Bottom line is to not let a lack of gear cutters and indexing head scare you off a one or two tooth repair. It's fussy work but it can be done with simpler tools and with simple temporary indexing schemes and if you have a mill with a simple to make gear tooth flycutter ground from HSS along with a magnifying glass to check the fit of the cutter in the groove.
                  Chilliwack BC, Canada

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                  • #10
                    Originally posted by BCRider View Post
                    Plunger, there may not be a video on fixing a gear on specifically a South Bend but there are lots of videos on YT on repairing broken gear teeth. Try the search terms "replacing broken gear tooth" and "repairing broken gear tooth".

                    One of the lower tech repairs that deals with a lathe's back gear setup also includes a peek at a single tooth shop ground flycutter for the cutting of the tooth. For a one time repair we do not need a whole set of gear cutting wheels.

                    https://www.youtube.com/watch?v=n5S-5B7jomU

                    But wait.... order now and you'll also get.....OK, I can't find it now but there was a video on repairing broken gear teeth on larger sized gears such as we have on our lathes where the guy brazed in a new tooth then carefully cut into the blob of brazing with a hacksaw and then filed it to shape. That's right, hand filed it. And while it didn't show him doing so I'm going to assume that this was done in concert with meshing the tooth/teeth being shaped with another gear and looking at and touching up any shiny spots until a good mesh was achieved.

                    Bottom line is to not let a lack of gear cutters and indexing head scare you off a one or two tooth repair. It's fussy work but it can be done with simpler tools and with simple temporary indexing schemes and if you have a mill with a simple to make gear tooth flycutter ground from HSS along with a magnifying glass to check the fit of the cutter in the groove.
                    My mate removed the spindle and informs me there is damage to the spindle bearings as well as headstock journals.But google tells me this looks worse than it is in reality. I dont know if this is true. I will get pics soon.There were no wicks to both the bearings.With regards to the gear on the spindle its not one or two teeth damaged but most.
                    Thats why i was wondering if the entire gear cant be machined off and a bigger gear made that keys to the back of the spindle. It will throw the meshing out but it seems there is some sort of tumbler that shares two exact same size gears. If these two gears could be changed to smaller gears could it not be a simpler way.

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                    • #11
                      Repair is possible, or even replace it with another gear. I would bet that a motorcycle transmission would have some good gears in that size range. BTW, many of the South Bend lathes had plain cast iron bearings, and the spindles were finished mirror smooth. Proper oiling is essential.

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                      • #12
                        The reason the gear in question is machined into the spindle itself is to get to minimum size however the changewheel gearing doesn't start until after the tumbler reverse. So you can turn off the teeth and shrink or locktight but not anything hot and larger one on. Then either allow for it in the thread calculations or make the input gear to the tumbler reverse match it.

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                        • #13
                          I dont quite understand the tumbler as its not in front of me but do they actually effect the gear train ratio.Could any gear here not be used .Isnt it more like an idler gear ,just changing direction.I tried looking on southbend group but could not find a repair for this either.

                          I did find an interesting line bore thread though.The guy line bores using the lathe bed itself and a steady rest. He then machines a p bronze bush/bearing.

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                          • #14
                            Yeah, the tumbler is just two gears of the same size. But without modifications to the tumbler's frame you can't switch them. The tumbler arm is designed to let the tumbler gears engage with the gear on the end of the spindle. And that means that the tumbler swing axis is set at a specific radius to allow the tumbler gears to engage the gear on the spindle and the gear train below that. So you'll find that you're pretty well stuck with using the proper gears.
                            Chilliwack BC, Canada

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                            • #15
                              As long as you use the same number of teeth on the end of the spindle then nothing else needs to change

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