Sharp 1764T lathe, No clutch?
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    Default Sharp 1764T lathe, No clutch?

    I have a Sharp 1764T Lathe that was designed without a clutch/brake. Just on or off to the 7 1/5 hp motor which on start up draws over 50 amps without a load other than the chuck and rpms above 1000 then trips the breaker. I've come to understand that a lathe of this size usually has a clutch and the motor keeps running when the spindle is stopped with the stop and start lever on the carriage so it doesn't have to start from a dead stop. It does have a manual brake stop foot pedal. What's a good solution for this? I see DC Clutch/brakes are available and there is room for one to be installed on this lathe. It might mess with the manual brake though but I could work around that.Suggestions? Thanks.

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    VFD. Adjust the ramp-up and ramp-down to suit. Install a braking resistor and get prompt decel, no need to mash the brake pedal.

    Regards.

    Mike

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    Not all THAT unusual not to have a clutch,had a ENCO 18X40 no clutch ! Took 15 HP rotary converter to gat it to start reliably. Most cheaper Asian lathes clutchless.

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    My Smart & Brown 1024 is another example of a high quality machine built without a clutch. In this case it makes for a very simple mechanical layout, which i found attractive on an older machine as having less to be well worn or go wrong. However start up is bit brutal and mildly scary with reasonable size job mounted. I'd not care to run an 18" machine, nearly twice the size, without a clutch.

    As Mike says VFD is probably the best option if motor voltage is compatible and electrical control layout permits without major alterations.

    If I were to set up such I'd have a two stage, lever style, start control. First step bringing it up to a slow speed to verify clearances, mounting and so on. Preferably with a heavily restricted current to minimise power so if something does contact damage will be light. Second stage to bring it up to running speed. Ideal would be set-up where you have some control over acceleration rate. Not something you'd explicitly need but i can think of case where it would be nice to have. Not fan of twiddling the pot up every start, especially with gear head lathe.

    Clive
    Last edited by Clive603; 05-20-2019 at 08:55 AM.

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    You can buy a soft starter too if you don't want a VFD.

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    Thanks for all the suggestions. I'm glad I'm not alone on this clutchless thing. I have used VFDs before on my smaller ,1-1 1/2 hp 3-phase motors and liked them because of single phase to 3 phase ability plus the programmable soft start and other features. Now I have a 15 hp rotary phase converter so I haven't been using them although I may again ,its nice to be able to vary the speed with out changing belts. I'll look into a 8hp Vfd ,I'm thinking even a used one may be expensive. But then so are eclectic clutch/brakes. I'm also curios about the soft starter.

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    Quote Originally Posted by lostpines View Post
    Thanks for all the suggestions. I'm glad I'm not alone on this clutchless thing. I have used VFDs before on my smaller ,1-1 1/2 hp 3-phase motors and liked them because of single phase to 3 phase ability plus the programmable soft start and other features. Now I have a 15 hp rotary phase converter so I haven't been using them although I may again ,its nice to be able to vary the speed with out changing belts. I'll look into a 8hp Vfd ,I'm thinking even a used one may be expensive. But then so are eclectic clutch/brakes. I'm also curios about the soft starter.
    Not knowing where you stand on "expensive," but this is a very nice unit:

    WJ200-055LF 7.5HP 5.5kW 230V VFD - Hitachi

    Regards.

    Mike

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    The soft starter is not much less expensive. This one does require a cooling fan as well.

    Stellar SR22 Series Compact Soft Starter: 40A, Trip Class 2/10/20/30 (PN# SR22-40) | AutomationDirect

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    Thanks for the links guys. These are better prices than expected and may end up going that way. I'm still curios about the motor clutch/brake, does any one have experience with these? I know I would need a separate DC power supply but could wire it so the carriage mounted start stop lever functions as expected by most.I've been hearing " I've never heard of a lathe this size without a clutch"

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    I put a Warner electric clutch/brake on a lathe with a 5 HP motor many moons ago. I spent over $575 on the package back in 1978. I can imagine what it would cost today. Ken

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    Quote Originally Posted by 4GSR View Post
    I put a Warner electric clutch/brake on a lathe with a 5 HP motor many moons ago. I spent over $575 on the package back in 1978. I can imagine what it would cost today. Ken
    Ken, were you happy with the end result? Does it require a DC power supply for the clutch?

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    Ken,do or did you have a Sebastian/Sheldon 13" gearhead lathe. I talked to someone in Victoria Tx that owned one a few years back. I still have mine.

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    Ken, I found our correspondence from 2013. I'll contact you off list when I have the time.Steve

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    Hey Steve, I lost contact with you,Sorry.

    No, I don't have the 13" Sheldon Sebastian lathe any more. I sold it to a guy in Laredo. Kept the taper attachment off of it and put it on the 15" Sheldon lathe I bought to replace the 13" Sheldon. Have it running, still have a few things to finish up on it.

    The clutch-brake I installed on the lathe way back when worked great! Did not stall the 5HP motor at all in any of the speeds. The brake was nice, you could set it to stop on a dime or come to a sliding stop by a few RPM's. As for DC voltage, the modul took in 120V AC and converted it to DC for both the clutch and brake.
    If I had the chance to do it again, I would. BUT! today, you can virtually do the same with a VFD. In fact, you can do it with a VFD. Ramp up you can set where it don't need a clutch, and braking is as simple a making a program change. IF your wanting to stop on a dime, you will need a big resistor. I haven't needed to install a resistor to any of the VFD's I have installed, I have no need to stop my lathes on a dime.
    Running a big VFD on a RPC should not be an issue either. Haven't done it myself, there are many here that has done so.

    Ken

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    Thanks Ken,I'm much more familiar with VFD's than the clutch/brakes which would also require mechanical modification. I'm glad to know a little more about them for possible future applications but I'll go the VFD route on my lathes. May try it on my 13" Sebastion first since I have a VFD already that will be appropriately sized for it's motor. All my 3 phase motors would have VFD's on them if I didn't have the rotary phase converter. They are a good solution to phase conversion plus being able to vary the motor speed and as you mentioned ,they can be programed in many different performance configurations.Steve

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