New Okuma LS coming home!
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  1. #1
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    Default New Okuma LS coming home!

    New Okuma LS, well new to me!

    This is a 21x50 with a 10hp motor made in 1966. From what I could tell everything is in great condition, ways look good, everything is tight and holds good tolerances. all of the the handles turn smooth with no play. Runs super quiet.
    okuma-1.jpg

    It looks like someone did a quick overspray years ago that is now starting to peel. I think I can remove this with a scrubbing pad and some elbow grease. The original paint looks good just the normal wear that you would see over time.
    okuma-4.jpg

    My main issue is power. I have 220 single phase with a total of 55A available. When the lathe kicks on it draws about 38A (Running 3-phase)for a second or two then goes down to about 6-8A. I am a home hobbyist, so most likely this would be the only machine running at a time...but the air compressor (18A) might kick on or maybe my son turns on the wood lathe.

    From what I have researched I have a few options...
    1. a 20hp VFD(expensive). I wonder if I could get away with a 10HP-15HP VFD with a slow start???
    2. Change to a 5hp or 7.5hp Motor and 10-15hp VFD
    3. Change to a single phase 5hp-7.5hp.

    Thoughts???

    Thanks!

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  3. #2
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    My lathe came with a 4 Kw motor 575 three phase. I changed to a 3hp single phase 220 volt motor and couldn't be happier. Most "hobby" lathe cuts are maybe a horsepower at most so if you can get a single phase motor to fit your machine you should be fine.

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    Quote Originally Posted by 706jim View Post
    My lathe came with a 4 Kw motor 575 three phase. I changed to a 3hp single phase 220 volt motor and couldn't be happier. Most "hobby" lathe cuts are maybe a horsepower at most so if you can get a single phase motor to fit your machine you should be fine.
    Thank for the feedback!

    Are you running the same machine?

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    Mine is a Graziano Sag 14. 14 x 40 and about 3000lb, so a bit smaller than yours but still substantial.

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    Looks like I am going to change it to a 5hp 3-phase motor with a VFD.

    Any recommendations on the Motor/VFD brands?

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    Congrats, great looking machine! My first thought though was, that's gonna be a handful power-wise for a garage workshop. Glad you're sorting it out.

    -shaggy

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    Can you just get a vfd for the existing motor and set the start up speed to be on the slow side. Like a long ramp up soft start. VFD will cost more but no headache or added costs with new motor mounting, new pulley and/or bushing to fit the motor shaft, maybe new belt size....
    Or just a RPC?

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    Thanks for the suggestion. I had considered that...

    I was afraid that if I hit reverse or the break it might draw too much current and pop the breaker. Not knowing a ton about VFD's and how they regulate the power I'm still trying to figure it all out.

    Does anyone here have experience with this?

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    Got it home a couple of weeks ago. Overall everything seems tight and smooth. Ways have very little wear from what I can tell. A LOT of grease everywhere from years of use and not being cleaned, hoping there are not a lot of leaks that I didn't see, but there is grease all over the motor area and in the pan under the chip grate.

    I've spent the last two weeks slowly getting off the major layers of grease to look at the actual surface. There was a repaint at some point that was not done properly, or at least the wrong paint type. I think the short term goal is to get it thoroughly cleaned and lubed, looking for leaks that need to be attended to, and get as much of the loose paint off as possible.

    I need to change out the motor, it is a 10hp and I have a 55A (60A breaker) single phase to my garage, a 20hp VFD/RPC is 60A. I am thinking about going down to a 5hp or 7.5 motor...reducing my draw to 40-50A. Other things are connected to the supply, like my air compressor (18A). I know that the lathe only draws max current at start up and really heavy cuts, but I don't ever see myself doing large cuts on steel, so I doubt I'll ever draw that much current. This is a home shop and I am usually the only one working in there, so one major tool at a time.

    Thoughts on the motor size?

    Also, looking for a really good degreaser that won't eat the paint. I have spent a LOT of time with Dawn dishwashing liquid, it's just not cutting it!

    20201207_125315.jpg20201207_125338.jpg20201207_125636.jpg20201207_130313.jpg20201207_132556.jpg

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  13. #10
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    I have a licensed copy of your machine made in Korea (Dong Yang)
    Excellent machine , used every day and has given great service.

    My machine has a soft starting setup from the factory....Spindle start lever has two positions...first click starts the motor, and the second is a running contact.
    Pull the lever on and wait a second or so till the motor reaches full speed, then up one click to the running point....works well.
    Wonder if your machine has this feature...might not need to worry about initial starting current....

    If swapping the motor, personally i would not use a single phase motor on a lathe......can have adverse finish effects due to the single phase 60 cycle strobe effect.
    Nice machine, a shame to hinder its performance.

    Might consider a 10hp Phase Perfect. Better at handling starting loads. I have a 10 hp at home and it easily runs a Harrison 330S CNC lathes (10 hp spindle drive+ servos) and i am running that PP on a 35A, 220 service...
    (been temporary for the last several years)

    Cheers Ross

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    Original motor is pretty impressive, a star start / delta run affair; pretty sure you can run that on a 40A 240 single phase service via an appropriate rotary converter fed through a reactor to limit in-rush current.

    The star / delta config and it's controls is a bit difficult to sort out with a VFD.

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  17. #12
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    I have the same Okuma lathe with 10hp motor. I use a 10hp rotary phase converter (American Rotary) which is on a 50 amp breaker. Due to these lathes all being equipped with a star/delta soft start feature mentioned by AlfaGTA above, it has no problem starting... the breaker has never popped. I would not change the motor... just get a proper rotary phase converter.

    Jon

  18. #13
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    By the way... Your Okuma is 18", just like mine. The actual swing is 20", but it's considered the 18" model. The 20" model actually swings 22" and is very easily recognized because the lathe is basically the same but the headstock, compound, and tailstock are raised up on extra thick spacers. Yours doesn't have those thick spacers, just the regular ones, ergo 18".

    Jon
    Last edited by JDToumanian; 01-10-2021 at 04:37 AM.


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