Need Help!- Bmc ball screw support bearings

[JWC]

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?

[bloke]

use mm25bs62 fafnir. they are preloaded when tight. grease rocol sapphire2

[bloke]

aha. unless it has linear guides. in that case, fafnir mm35bs72

[JWC]

Getting the bearings(mm25bs62) is no problem. I need the proper tightening torque for the nut.

[JWC]

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.

[gthlm]

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.

[JWC]

Originally Posted by gthlm 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?

[JWC]

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