[jevs]

I have a Pratt & Whitney Tapemate Series C that I retrofitted. I believe it has some backlash because the screws can slide back and forth in the support bearings. I cannot remember how much since it has been awhile since I measured it, but I think it may have been .005" or so.

Does anyone know anything about these bearings or how I can take the slop out? I have not taken them out to inspect. They are angular contact like I see all over the net. I just can't find any explanation of how to adjust them.

I saw mention of some having a spacer that is machined for fit, but nothing is shown in these drawings.

I also read some about setting the preload with tightening the nut. I don't see how this can move anything unless the bearing starts to deform. It appears the races will already be compressed together unless there is a space left in there and preload is determined by tightness of the nut?

Please educate me? It seems like you would have to shim the outer races and then also space out the capture plate the same amount, unless there is a gap in there and the tightness of the nut dictates preload?

I am just not sure what the intentions are. Are you supposed to just buy a matched set of new bearings that are perfectly set when you get some wear, put them in, snug the nut down tight and they just end up right until they start to wear again? Or does the nut tightness have to be set in some special way....

Need help. I have to get as close to zero backlash as I can so I can machine parts for my router.
Thanks

[RICHARD ZASTROW]

Angular contact bearings USUALLY reach their proper preload when the nut compresses the inner races together and the outer races are firmly "trapped". Is the backlash over the entire screw length? If so ,it may be you need to check the ball nut; have the screw reground and fitted with oversized balls or ?

I personally don't use Oldham couplings because they have an amount of compliance, variable backlash depending on load. I usually specify bellows couplings that are rated higher than the motors peak torque.

I had backlash trouble on an old P&W but it turned out to be a couple of loose capscrews holding the ballnut support bracket.

Hope that helps, good luck.

Dick Z

[jevs]

So your saying there is no adjustment and you just have to buy a new matched bearing set?

It has been awhile since I checked this, but I narrowed it down to the bearings last time. The whole table/screw/nut moved back and forth together from what I remember. In other words the screw is moving in and out at these bearings both in X and Y. I did not measure any slop between the nut and the screw or the nut and the table. Of course this has been a couple years ago and I am going by memory, so I will check it again before I buy anything. I just want to know what is normally done when/if the play is in the fixed support bearings.

[underthetire]

Correct, however if the bearings were bad, they usually get pretty loud, and .005 is a lot. I'd check to make sure the outer collar is pushing on the outer race and not bottoming out, and the spanner nut is tight for the center. If all that is good, time for bearings

Sent from my G-Tab Quantum using Tapatalk

[jevs]

I will have to tear it apart again and check those things. Thanks. I mainly wanted confirmation that there was no adjustment and replacement was the answer. Adjustment would have been a cheaper answer though

[pippin88]

Shims. Whether you shim inner or outer race depends on which orientation the bearings are.

[RICHARD ZASTROW]

Maybe something simple? The bearing cap/retainer could be "hammered" a bit allowing the outer races to move a bit. That could be solved by a shimming between the outer race and the retainer as pippin88 suggested. Another simplistic thing; are the bearing retainer and the bracket the the support unit is mounted to securely fastened (tight capscrews)?

Might be simplistic and wishfull thinking but less expensive than a set of $$$$$ bearings.

Dick Z