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IndustryArena Forum > MetalWorking Machines > HURCO > Bmc ball screw support bearings
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  1. #1
    Join Date
    Jul 2003
    Posts
    71

    Bmc ball screw support bearings

    Where can I find the special tool to remove and torque the y axis ball screw support bearing nut on my 1990 BMC 20? Anyone know what the proper torque for that would be? Should I pack the new bearings with any special grease?

  2. #2
    Join Date
    Jun 2008
    Posts
    1103
    use mm25bs62 fafnir. they are preloaded when tight. grease rocol sapphire2

  3. #3
    Join Date
    Jun 2008
    Posts
    1103
    aha. unless it has linear guides. in that case, fafnir mm35bs72

  4. #4
    Join Date
    Jul 2003
    Posts
    71
    Getting the bearings(mm25bs62) is no problem. I need the proper tightening torque for the nut.

  5. #5
    Join Date
    Jul 2003
    Posts
    71
    I've replaced the bearings in the Y axis twice in the last seven years. I think the machine hits during calibration and that might be damaging the bearings over time. I'm going to move the limit switch stop about .05-.100 to see if that helps prevent it from slamming the back.

  6. #6
    Join Date
    May 2005
    Posts
    117
    What bloke was explaining is that the bearings have the preload ground in already. You tighten them up tight (as you can) and they will have the correct preload when the centres are tight together.

  7. #7
    Join Date
    Jul 2003
    Posts
    71
    Quote Originally Posted by gthlm View Post
    What bloke was explaining is that the bearings have the preload ground in already. You tighten them up tight (as you can) and they will have the correct preload when the centres are tight together.
    So there is no real torque spec on the nut?

  8. #8
    Join Date
    Jul 2003
    Posts
    71
    Turns out the bearings were not the backlash problem. Tightening the drive/timing belt cured the problem. I did obtain a Hurco service bulletin for the BMC20 bearings and found out that Hurco recommends that they be mounted DB instead of DF as is the common practice. The correct torque is 40-45 ft/lbs

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