South Bend 13" Lathe Motor
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  1. #1
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    Default South Bend 13" Lathe Motor

    I wanted to ask this question about my lathe motor. It's a 3ph, 3hp motor that uses a static drive to run it on AC 220 volt single phase. I am told that running it on a static drive will reduce it to 2hp, loosing 1hp in the process. I have a couple of friends I worked with that are electricians that could check it if I needed to. When I was doing the my first project I was drilling a 1" hole in 3-1/2" aluminum round. I had a good pilot hole, 1/2" diameter, so when I went to a 1" the motor started slowing down till it stopped. Is there a way to check it to see if it is weak or not? Thanks

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    A 13" is about a 1 to 1.5hp machine. Someone stuck a 3hp after the fact. Problem is the flat belt won't pull 3hp, belt will slip vs pull a true 3hp load. Now depending on how well all belts are adjusted, maybe vee belts slipped.

    But either way, I'd bet a dollar either flat or vee belts slipped under load. Not the motor came to a stop.

    And yes, you will lose hp with static converter, maybe thats why they went to 3hp. But i would still guess belt slipage.

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    Agreed - I have a 1 horse motor on mine, it will slip the flat belt when I am say drilling a 1" hole in cast iron. Aluminum shouldn't make it slip. And the 1/2" pilot for a 1" hole is too big, pilot hole only needs to be big enough for the web end of the drill, and maybe not that big if the drill has a split point. I'd think a 1/4" pilot would be generous, and maybe not even needed with aluminum.

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    Quote Originally Posted by texasgunsmith View Post
    A 13" is about a 1 to 1.5hp machine. Someone stuck a 3hp after the fact. Problem is the flat belt won't pull 3hp, belt will slip vs pull a true 3hp load. Now depending on how well all belts are adjusted, maybe vee belts slipped.

    But either way, I'd bet a dollar either flat or vee belts slipped under load. Not the motor came to a stop.

    And yes, you will lose hp with static converter, maybe thats why they went to 3hp. But i would still guess belt slipage.
    Quote Originally Posted by Rudd View Post
    Agreed - I have a 1 horse motor on mine, it will slip the flat belt when I am say drilling a 1" hole in cast iron. Aluminum shouldn't make it slip. And the 1/2" pilot for a 1" hole is too big, pilot hole only needs to be big enough for the web end of the drill, and maybe not that big if the drill has a split point. I'd think a 1/4" pilot would be generous, and maybe not even needed with aluminum.
    I forgot to mention I bought a VFD a while back. I even hooked it up but couldn't get it to reset so I could set the 60 cycles so at the time the VFD

    wasn't that important to get started other than seeing it run once. Getting the lathe running is first.

    I appreciate the comments and advice. Texas you will have to wait on the dollar bet until I can collect enough cans to cover it. Too many

    operations going on to take note of the belt slippage I was cautious of what I was doing. Mr. Rudd I agree with you on the size of the pilot hole.

    I'll keep it in mind what you said. It's funny, when I was in my early twenties I leased a welding and machine shop from my wife's Grandfather.

    Any serious machine work I would sub out to a good machinist friend who would come to the shop and do the job for me. I was well equipped

    except in experience.

    Later my wife and I and first child moved to Mobile Alabama. I worked at International Paper in Maintenance rebuilding all of the 19

    digesters in the pulp mill. Because I had just enough machine shop background I would take the digester caps to the machine shop and put them

    in a large lathe and machine the groove for a gasket. The digester caps were about 3" thick and maybe 36" diameter. One of the lathes I

    used was 30 foot long and had a swing some where around 48 inches, a large 4 jaw chuck in place. I also had a lot of time on the milling

    machines but over a course of 40 years not doing much more than running a drill press I have forgotten it all. Rather disturbing to me. I would

    imagine age has a lot to do with it all. If I loose the dollar bet you will have to remind me. Anyway I might not remember it all but my confidence

    has increased and I am constantly reading trying to catch up and have fun making chips.

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    As others have stated above, my 1 horse with a 1.25 service factor will slip the flat belt in my 13" just before it stalls. It will bog down a couple hundred RPMs before that point and start to heat up the overload protector... but it will ultimately slip before breakdown torque is reached.

    Sometimes it slips just a tiny bit when starting with the highest speed selected - and it's a very soft starting old motor. 1940's~50's capacitor start Century with the original Aerovox wax paper start capacitor. An order of magnitude less starting torque than anything made today, much less any three phase motor ever.

    Increasing the belt tension to compensate for this beyond reason will likely wear out the spindle bearings faster.

    If you've got a 3 horse job to do, then you need a 3 horse lathe to do it - not just a 3 horse motor. Your best option is to just step drill more slowly, feed less aggressively, use an annular cutter, grind a trepanning tool, etc.

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    Quote Originally Posted by Just a Sparky View Post
    As others have stated above, my 1 horse with a 1.25 service factor will slip the flat belt in my 13" just before it stalls. It will bog down a couple hundred RPMs before that point and start to heat up the overload protector... but it will ultimately slip before breakdown torque is reached.

    Sometimes it slips just a tiny bit when starting with the highest speed selected - and it's a very soft starting old motor. 1940's~50's capacitor start Century with the original Aerovox wax paper start capacitor. An order of magnitude less starting torque than anything made today, much less any three phase motor ever.

    Increasing the belt tension to compensate for this beyond reason will likely wear out the spindle bearings faster.

    If you've got a 3 horse job to do, then you need a 3 horse lathe to do it - not just a 3 horse motor. Your best option is to just step drill more slowly, feed less aggressively, use an annular cutter, grind a trepanning tool, etc.
    I never considered all of these factors in when drilling. You are absolutely right saying the motor is soft starting. I ended up boring the diameter out

    since I had to transition from a smaller size to a larger. The holes drilled around the flange end were randomly placed but the rest is according to a

    drawing I was given. Appreciate all of the advice and suggestions


    20200306_184438.jpg20200308_222953.jpgimg_3009.jpgimg_3268.jpgimg_3276.jpg

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    A few more pictures. The bolt pattern was random, no need to lay it out perfect


    20200303_162918.jpg20200306_162237.jpg20200308_223104.jpg

  13. #8
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    Quote Originally Posted by Greenlee52 View Post
    A few more pictures. The bolt pattern was random, no need to lay it out perfect


    20200303_162918.jpg20200306_162237.jpg20200308_223104.jpg

    I know this is a baby project but it did make a lot of chips. In the center picture the cone is cut off of the aluminum bar stock. I made a tapered spindle to hold the cone so I could finish the nose. Worked well for my needs. I can't wait until I can get this lathe going again, haven't been able to work on it yet. The same goes for everyone, you have to crawl before you can walk and I was holding onto the top of the crib rail. lol


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