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IndustryArena Forum > MetalWorking Machines > Okuma > Okuma LB-12 Spindle Rebuild
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  1. #1
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    Okuma LB-12 Spindle Rebuild

    Hello good neighbors - I have an LB-12 from the late eighties with what I think are the original spindle bearings. They are starting to growl so I'd like to replace them asap. Does anybody have any information on rebuilding the spindle (did Oluma make a manual for this?). I'm looking for information on consumable parts, tolerances, bearing nut torques, etc.

    I was able to get the modern bearing numbers from NTN.

    I appreciate that this is a precision repair requiring special tools and techniques, and that there will likely be several comments to the effect that I shouldn't even touch the spindle, but I'm a small one-man shop that doesn't have the funds to send the spindle out for professional repair so I'll be performing this myself.

    Any help that anyone could provide would be greatly appreciated. Thank you.

  2. #2
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    You don't need any special tools.
    1. take the spindle cardridge from headstock.
    2. mark "0" point of bearing. remove old bearings.
    3. remove the spacer.
    4. put on new bearing untill proper tension
    5. measure new lenght of spacer. check if original spacer fits.
    6. take away bearing
    7. put on the prepared spacer
    8. put on new bearing and nuts and all.
    This will ensure proper tension of bearing. It's not a manual nor training material. Just brief description.

  3. #3
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    Those spindles get done it the field. No need to send them anywhere. Only special tools you may need are gauge blocks to determine correct preload and a thermometer so you don't cook the grease during run in. Proper run in can take 1-2 days sometimes. Oh, and make sure you get Klubber NBU-15 grease for the spindle. Nothing else works well.

  4. #4
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    Thanks for the responses - I'm glad to here that it should be a straight forward repair.

  5. #5
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    Wink

    Quote Originally Posted by underthetire View Post
    Those spindles get done it the field. No need to send them anywhere. Only special tools you may need are gauge blocks to determine correct preload and a thermometer so you don't cook the grease during run in. Proper run in can take 1-2 days sometimes. Oh, and make sure you get Klubber NBU-15 grease for the spindle. Nothing else works well.
    +1. Only use NBU-15 and use an oral syringe to inject the correct amount of grease in cc's or ml's. Too much grease will kill the bearings as they can not dissipate heat. Also,the preload is very important.

  6. #6
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    as a former Okuma service engineer in CA, I can confirm that the advise you have been offered is correct, but no-one has explained "how".

    After removing the spindle, clean everything with white spirit removing all grease, stand the spindle on its nose and start with the front bearing. It should be a tapered bore, i.e. the spindle has a taper diameter behind the spindle nose.

    assemble the inner bearing without the adjusting spacer and lightly tighten the nut, slide the new clean and dry outer bearing sleeve up and down the bearing and tighten the with the preload nut until the outer sleeve just holds under its own weight, you should be able to rotate the outer freely but it should not drop from the bearing inner. Now measure the gap where the spacer was with gauge blocks. grind the spacer to this width minus a couple of microns, disassemble and reassemble with the spacer and check. repeat the process for the rear support bearing. Find out from Okuma or NTN the exact quantity of grease per each bearing in cc's. i.e; 2.5 or 4.5 etc; use a syringe with a narrow hole and run the grease into the bearings evenly.

    after re-assembly, run the spindle up in 500rpm steps, monitor the temperature at each stage until it flattens off and begins to fall. you need to do this up to the maximum speed of the spindle.

    the temperature should not rise more than 30 degrees celsius over room temperature, if it does, stop and start the whole procedure again.

    this can take a morning, a day or longer but after running in the spindle will be good for another 5 years if you get it right.

    finally, make sure if you have a gearchange that the lube pipes are positioned so oil cannot wash out the kluber nbu 15 grease.

    long winded I'm afraid, but that is the only way.

  7. #7
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    Good instructions.
    One thing,what was aready mentioned but this is most common error when new bearings are installed:

    1) Clean bearing from factory oil
    2) Proper amount of Kluber grease.
    3) VERY IMPORTANT:
    You have to run spindle very slowly at first. (5min)
    After that:
    (0.3x nmax 30sec, rest 1min ) x 20
    (0.5x nmax 30 sec, rest 1min) x 10
    (nmax 30sec, rest 2min)x10
    Just in case drive this sequence 3 times.
    If any heat is generated,stop and wait bearings to cool.
    It's easiest to do little NC program......

    This all is done to pull out extra grease from bearings.
    And of course when starting machine, always remember to warmup bearing.

  8. #8
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    Smile

    "green button",

    what you have written is good, but if you read my post carefully it covers all of these points.

    remember I am an Okuma trained service engineer and the sequence I have recommended is how Okuma do it in the field.

    but your way could also work.

  9. #9
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    No doubt about your skills.
    Just want to make sure people clean & warm bearing correct.

  10. #10
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    cncseryeng and Green Button.

    Both of your advice helps a lot. And I am using your advice for both of my LB15 and LB9 machine. REMEMBER the Kluber grease is really the key in this point. As we have tested other and they bearing worn prematurely.

    Thanks.

  11. #11
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    Also take precaution of the Back-to-Back angular contact bearing's orientation.

  12. #12
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    Re: Okuma LB-12 Spindle Rebuild

    Hello - sorry for bumping this old thread.

    I got a LC 30 that whines from the spindel and having a hard time making a good surface like my LB 15 with same feeds and speed.


    Will this be the same procedure for replacing spindel bearings?

  13. #13
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    Re: Okuma LB-12 Spindle Rebuild

    Hello,
    I have LB15 from 90' and now its time to change spinde bearings. Originally its NTN bearings but I was asking NTN suplier and they couldn't help me in this case. So my question is, where do you guys order bearings fro your okuma spindle?
    PS I contacted Okuma dealer, but he was not interested in such an old machine.. Sorry for my language too

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