My new to me lathe, overpowered?
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  1. #1
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    Default My new to me lathe, overpowered?

    I had to take it apart to lift it up there but I got it! Very happy! Apparently this was an ongoing project until recently. All new felts, paint has zero scratches, everything is tight and smooth. I bought it from a part time machine dealer who got it because he sold the a guy a bigger south bend. He saw this one, asked about it, gave the guy a motor (it needed a new one)so he could do tests cuts and run through the lathe to see if he wanted it.

    Then I came along and got it. I know nothing about lathes so I wanted to go through a machine dealer. He took a few days taking it apart and looked over everything.

    I'm concerned this motor is a bit much for this little 9 inch. I took a picture of the plate. If I need a new one that's fine, I will sell or trade this one if I need to.
    Attached Thumbnails Attached Thumbnails 20210719_204839.jpg   16267465375551828660979177133028.jpg  

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    Overpowered and oversped by twice the speed.

    You should probably want a 1/2hp or 3/4hp. But that does not nearly bother me as much as the speed. You really want a motor in the 1800rpm range. That 3450 will wreck that lathe unless they did some crazy diameter changes to pulleys, and thats doubtful.

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    Quote Originally Posted by Matt_50 View Post
    I'm concerned this motor is a bit much for this little 9 inch. I took a picture of the plate. If I need a new one that's fine, I will sell or trade this one if I need to.
    1 1/2 HP is easily DOUBLE what it is comfortable with ... if not triple.

    3/4 HP is about all it can stand, and 1/2 HP is plenty.

    That said, belts slip.

    With a skosh of adjustment, you can even chose by how much.



    Not a show-stopper, IOW.

    One does wonder, however, if you would be better-served with an approx 1750 RPM 4-Pole instead of that ~ 3450 RPM two-pole?

    The spindle bearings are not noted for high-speed endurance, so a lesser motor RPM might insure all your available belted ratios are useful?

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    Belt pictures. And motor.
    Attached Thumbnails Attached Thumbnails 16267492349296177924954935986569.jpg   16267492700908820019729810417344.jpg   16267492978497551899749971538583.jpg   16267493177172999749073502598896.jpg  

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    I have this motor I can steal off a machine I dont use. I can always swap it back after I find the perfect motor. Open to suggestions and advice on motors...

    Quick measurement looks like the base is the same.
    Attached Thumbnails Attached Thumbnails 16267506372855855560517264106851.jpg   16267506698347606415308302746563.jpg  

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    Digging around I found this one too.
    Attached Thumbnails Attached Thumbnails 16267525520815534359289942730278.jpg  

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    The 1/4hp will work till you get a 1/2hp.

    Look up, google "south bend how to run a lathe 55th edition". Find the speed spec for yours. My guess is top spindle speed should be about 900 rpm. Thats top spindle speed.

    With the 3450rpm motor and vee pully dimensions I'm showing the large vee pulley turning 941rpm. But that's the large vee pulley, not spindle. Looking at flat belt cone pulleys, it appears the middle pulley is 1 to 1, so we'll say 941rpm of spindle, with middle flat. Where the large flat pulley of spindle would spin slower than 941, but the small flat faster than 941.

    Pulley calculator anywho:
    Pulley Calculator. RPM, Belt Length, Speed, Animated Diagrams

    Of course changing to that 1800rpm 1/4hp will change that, or any 1800-ish rpm motor. Should put top spindle speed, using the small flat of cone pulley right in the correct vicinity.

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    Thank you for the calculator link.

    Center to center is 10.5 inches. Big pulley is 11 inches. Small is 3, distance between the two pulleys is 3.

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    Perfect motor is a ~1725 rpm 230v 1/2 HP 3-phase motor, powered with a 115v input variable-frequency-drive. (heck a 1/4 hp is probably fine for the vast majority of work, and a 1/3 would definitely do, the belts on the lathe will slip before stalling a 1/2 hp motor).

    (motor example: Lesson 192038 1/2HP 3 Phase 1695RPM 230/460V Electric Motor | eBay)

    3/4 hp is overkill, >3/4 hp too big.

    VFD ~$150 (example,L510-1P5-H1-U | Teco Westinghouse |

    Make sure it is a 115 volt input so it can be plugged into any standard 115v outlet. The 3p motor is smoother, and with VFD infinitely variable speed, fwd/rev, accel, decel, no jerking starts, rarely need to change pulleys cause of variable speed, and you can tweak out resonances. Don't buy used motors off of Ebay, unless they look pristine, new ones are cheap on ebay.

    I have a 10K and had all sorts of vibration anomalies with two different motors (quality baldor single-phase 1/2 hp tefc motors), till installing the 3P motor and VFD. Cheers

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    Quote Originally Posted by Matt_50 View Post
    I have this motor I can steal off a machine I dont use. I can always swap it back after I find the perfect motor. Open to suggestions and advice on motors...

    Quick measurement looks like the base is the same.
    The Marathon should do yah.

    1725 RPM, decent brand and 1/3 HP could do yah fine even "for permanent".

    OR.. and I recommend this.. run it for several months.. until you know your lathe better, know what you are doing / will DO with it better.

    Because.. you MIGHT decide to sell or trade it and go for a larger lathe. Or one that is in better overall condition .. or ... give it up and take up making stained-glass lampshades, woven belly-button-lint earplugs or .. clever excuses for doing ....nothing much atall?

    So don't put money into one - nor a VFD - if you are not already an experienced hand and comfortable with your direction.

    Keep it cheap, it's fun.

    Bust the budget, the fun wears thin.

    DAMHIKT!

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    I would recommend a TEFC, (totally enclosed fan cooled) rather than a ODP, (open drip proof) mainly for the resistance to chips and oil. Jim

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    And have a 3 wire plug..it can also be a good idea to have an extra ground wire on a machine.

    it is not uncommon for a motor taken from another device to not have 3 wires or proper grounding because they are bolted to a grounded device...so it is up to you to be sure the motor is grounded. Staking a wire to a motor frame/body screw can make a decent ground wire.

    Plus some guys use the plug-in for a switch. A plug and socket are not a switch and so a motor will quickly burn away the plug prongs or socket and soon it will not properly ground even with having 3 wires.

    The likes of a lamp switch are not good enough for a motor. you need to have a real motor switch good for higher amps. Usually, one stating 30 amp is good for up to 2 hp or so.
    Last edited by michiganbuck; 07-20-2021 at 10:52 AM.

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    Quote Originally Posted by michiganbuck View Post
    The likes of a lamp switch are not good enough for a motor. you need to have a rel motor switch good for higher amps. Usually, one stating 30 amp is good for up to 2 hp or so.
    Yup. It's about contact life interrupting inductive loads more than just amp rating. Most "common" would be what Big Box used to call "oil burner" switches for furnaces with what was often the only motor of any size in a modest residence. Unless there was a deep-well pump.

    Even so.. a push-button electrically latching or "Magnetic Motor Starter" function, wherein IF power is interrupted, the motor goes OFF and stays OFF until manually cycled, is a good idea on any fixed rotating machinery, even small hobby lathes.

    That also makes it easy to add an E-Stop. Which can be found for as little as five bucks.

    Doing it "right" gets a body off to a better start for moving into larger and more hazardous machinery later.. or just "elsewhere, now and then", visited/borrowed.

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    Thank you for the feedback guys. Both the 1/4 hp motor and the 1/3 hp motor are open. I was going to make some kind of shield until I pick up a new motor. I don't want to buy a used one so I'll keep an eye out for a 1/2 hp 1725 motor. I was going to ask about a switch. Both of these motors have a switch built in to the back. Leaning over for on and off sounds like a recipe for disaster. I was looking at my router table and thinking a switch like that would do. Thoughts? Both motors are three prong plug.

    I need to grab a sleeve for the pulley. That big motor is 5/8 shaft, these two are 1/2 inch. Is there any reason to change the pulley? Or should I stick with just a new sleeve and reuse the existing one/size?

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    That big motor at 3450 will run the lathe at double speed and so may be hard on bearings and cutting tools.

    Plus if you have a wreck with that much power you can break the machine.

    If you pulley size it down to make acceptable RPM you will still have machine breaking power and be using a lot of electric bills.

    1/3 hp motor would be Ok but should be the closed type so chips don't get into the works.

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    Quote Originally Posted by Matt_50 View Post
    Thank you for the feedback guys. Both the 1/4 hp motor and the 1/3 hp motor are open. I was going to make some kind of shield until I pick up a new motor. I don't want to buy a used one so I'll keep an eye out for a 1/2 hp 1725 motor. I was going to ask about a switch. Both of these motors have a switch built in to the back. Leaning over for on and off sounds like a recipe for disaster. I was looking at my router table and thinking a switch like that would do. Thoughts? Both motors are three prong plug.

    I need to grab a sleeve for the pulley. That big motor is 5/8 shaft, these two are 1/2 inch. Is there any reason to change the pulley? Or should I stick with just a new sleeve and reuse the existing one/size?
    One of the most common of bushings out there, that size. Usually split to clear a keyway. JF use it.

    The pulley seems to be the right size of the lower-RPM arredy?

    You'd only want to change it if whomever put the faster motor on DID use a smaller pulley to limit top RPM overspeed risk at the spindle bearings.

    Partly because it will for-sure be too small for decent grip and belt life.

    Light Vee belts's fare progressively more poorly at pitch diameters under about 3 to 3 1/2 inches, last a long time if the smallest pulley is above that size.

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    For comparison, my 13" lathe came with a 1-1/2hp motor at 1725 RPM.

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    How about this for a switch? The marathon motor has a toggle switch built into the back. I think I'll just leave that "on" and add something like this. Thought? The motor cord is long enough to cut and splice the switch into.

    120V Magnetic Switch at Grizzly.com

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    Quote Originally Posted by Matt_50 View Post
    How about this for a switch? The marathon motor has a toggle switch built into the back. I think I'll just leave that "on" and add something like this. Thought? The motor cord is long enough to cut and splice the switch into.

    120V Magnetic Switch at Grizzly.com
    looks good, plastickbox? be sure the machine is grounded.

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    Exclamation

    FWIW, my SB 9A has the original factory GE 1/2 HP motor at 1725 RPM.
    In back gear, if I stall it doing something stupid, it has enough balls to twist and bend the entire machine -- you can actually watch the compound, cross-slide, saddle, and bed twist while the chuck tries to snap off.

    1/2 HP is plenty. I have the 12 speed setup with flat belts, giving 50 RPM way down low, and 1200 RPM on top. So far it does everything I need as long as I do my part.


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