South Bend 10K drive
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  1. #1
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    Default South Bend 10K drive

    Hello, New to the forum, forgive me if this has been posted before. Recently bought a South Bend 10K light lathe with underdrive cabinet, mid 70's era. Love the lathe, but am disappointed by it's lack of power, stalls out even during light cuts. Drive is all original, using a solid state phase converter, replaced the flat drive belt (squirrel daddy mfg.) Are there any cost effective improvements to give it more power ? Thanks, Dave

  2. #2
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    Most solid state converters only start on three phase, one generated by a capacitor, and run on single phase. That gives you a power reduction on an already underpowered machine. Look for a real phase converter such as a rotary one. Do not replace the motor with a single phase one. They will not reverse on the fly but continue to run in the same direction, a serious drawback when you are being rolled up in the chuck.

    Don't invest too much. If you get into serious lathe work, it will not take long to realize the shortcomings of the 10K and want something better.

    In any case, always make sure the spindle oil cups are full. These lathes have plain bearings whose useful life when dry is about the same as your car when it is out of oil. With the belt loose, put a dial indicator on the top of the spindle and pry it upward with a stick. If you get more than a few thousandths movement, it means that it has been run out of oil.

    Bill

  3. #3
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    Thank you, I do remember hearing that solid state converters can produce reduced power. Would be willing to try a VFD, but wonder if they would also produce less power ? will also check lubrication.

  4. #4
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    A properly sized VFD will give you full power and on-the-fly speed control for probably less than 200 clams. If you only have the one three phase machine, and don't plan on more three phase machines, a rotary converter might be overkill.
    I have two three phase mills on VFD's, and intend to convert my lathe back to three phase, I'll be sticking with VFD's.
    I have both mills set up with remote panels to control the VFD - changing speed is as simple as twisting a knob. Flip a switch for reverse (after stopping of course), and have a BRB (big red button) if things go pear shaped.
    Reverse on the vertical came in handy yesterday, had to get a busted screw out of a part. Used a LH drill, about halfway in the screw decided to back out.
    You do realize there is a dedicated SB forum on the board, yes?

    Edit - I have these on both mills as well. In combination with the VFD I can fine tune to optimal cutting speed. You enter cutter (for mill) or part diamter (for lathe) and it directly reads out SFM cutting speed as you adjust.
    Home of the MachTach

  5. #5
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    Remember that when running a VFD you need to run it in sensorless vector mode(most drives today have this mode) not volts/hertz mode. Volts/hertz mode will have very low torque at lower speeds while in sensorless vector mode you can get pretty close to zero speed while maintaining rated torque.


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