southbend 9a Belt adjustment
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  1. #1
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    Default southbend 9a Belt adjustment

    Anybody know how to adjust the Belt on a southbend 9a lathe? My belt seems to wander off the pulley. This is the under drive model where the lathe sits on a steel bench configuration and the motor is underneath the head stock with a metal door for access. I am going to replace the stock motor with a 3 phase one and wire up a vfd to it. I also plan on replacing the old leather belt with a serpentine belt so I want to figure out the belt adjustment procedure before I proceed. Any help is greatly appreciated.

    s-l1600-3-.jpgmissing-turnbuckle-belt-tensioner.jpg

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    it looks like you are missing the handle too.

    the handle does a 180 degree rotation to raise or lower the counter shaft and the belt tension is built into the same linkage. handle gets rotated past 180 degrees and hits a hard, adjustable stop and that locks the belt tension into the linkage. yours is significantly different than mine. looks like your handle might be on the left side of the cabinet. mine would be located through the hole in the cabinet right above the door handle.

    you can probably find a drawing in the manual for your lathe that shows you how its supposed to go together

  3. #3
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    I know of a couple of reasons that the belt might wander off, It's unlikely but the belt could have been made incorrectly, Or stretched more on one side than the other. This could cause the belt to wander off the pulley. A quick check is to mark one edge of the belt, Then remove the belt and turn it so the mark is on the opposite side. If the belt tries to wander in the opposite direction, you know it's a bad belt. The second and most likely problem is that the Pulleys are not lined up correctly, or the spindle and the counter shaft is not parallel to each other. This could be something simple like some of the bolts loose on the mounting bracket, to something hard to fix like a worn-out bushing or Worse the cast bearing point. you can check the pulley alignment using the straight edge, preferably one that is the same width as the pulley step. Otherwise just line it up as close as you can. if the pulleys are in line, check to make sure no one has put any shims under the headstock or tailstock area of the bed feet. Next measure the distance from the chip pan to the counter shaft. There should not be any difference between the two ends of the shaft. let us know what you find.

    stay safe and have fun.

    Joe.

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    Quote Originally Posted by johansen View Post
    it looks like you are missing the handle too.
    The handle is just visible on the left hand side. The empty holes above the door are where the original switch resided. Interesting - the base of the compound indicates a 10k, but the tailstock appears to be that of a 9". And the compound has a large dial, while the crossfeed has a small dial. What's the serial number and the catalog number? The SN is stamped into the ways at the tailstock end, between the carriage v and the tailstock flat, the catalog # is on the gearbox plate.

    Paul

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    If the tension is right on the belt, walking could be caused by a crooked splice. Mine is stitched and if I get that crooked it walks to the tight side of the belt.

  6. #6
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    In your picture, it looks like the cone-pulley tension adjust, raise/lower linkage is missing. The cone pully tension is adjusted by adjusting the turnbuckle between the handle linkage and mounting bracket. I suppose the pully mount casting could also be skewed. Motor belt tension is adjusted just by moving the motor.
    You'll like the VFD and 3p motor, that's a major improvement and will get rid of most vibration. You may not need that aluminum motor mount adapter plate with a standard frame motor. Cheers.

    img_5634.jpg


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