Bearing shields ZZ tightness

You all know what a "shielded" bearing is, type Z or ZZ...

Well, our mgmt has decided that shields must be ABSOLUTELY incapable of any rotation.
We buy 100s of thousands of bearings from another vendor and re-ship them to our customers or build them into assemblies.
We have a guy with a little hooked pick, digging into the edge of the shields, trying to make them budge.
About 50% of them can be shifted in this way. I would call them extremely tight, but they officially refer to them as "loose shields."

We are supposed to re-work them. We have had two engineers, two machinists, and a mechanic working on this for two weeks, without success.
And are now embarrassingly late shipping an order.
Using both a manual lathe and a CNC machine, we have tried over 25 different tool geometries and by the time I post this it will be many more.
We have scanned the bearings, shields, and tools with a digital microscope ad nauseum.
Everything we try, either damages the shield or results in "loose shields."
Some are so tight, that only one guy here is strong enough to move them. So he's the guy assigned to do the checking.

We had the vendor send us the tool that they use, and of course it is just like things we already tried.
Usually I don't give up on anything, but now when I see the engineers and managers standing around the machine, I find something else to do.

(Spell Checker says I misspelled "ad nauseam" so lets just say, "I'm ready to puke.")

Why is this 'non-negotiable?'
What does your vendor say?
If the seal is so loose that it will not rotate, It is not going to 'seal.' On top of that the friction of the grease inside may cause it to turn anyway.
Sounds like a 'designated expert,' with more designation than expertise is in over his head.

Clean with solvent of choice then add a dab of glue. Just do them all no need to pretest.
Bill D

Clean with solvent of choice then add a dab of glue. Just do them all no need to pretest. Just make sure it does not stick up above the outer race thickness.
Bill D

gwelo62 said:

Why is this 'non-negotiable?'
What does your vendor say?
If the seal is so loose that it will not rotate, It is not going to 'seal.' On top of that the friction of the grease inside may cause it to turn anyway.
Sounds like a 'designated expert,' with more designation than expertise is in over his head.

Click to expand...

It's a shield, not a seal. I would expect a seal to stay with the inner or outer bearing, but expect a shield to be maybe a bit loose between the 2.

OP: has management explained why they want the shield stuck instead of floating? Seems like a minor difference to me.

If you follow BillD's idea make sure you glue the seal to the non-rotating race only.

'Shields' don't contact the inner race. The only force causing them to rotate would be a defective product design. Sounds like either a problem that doesn't exist or your company needs to find out where they screwed up in designing the product.

I too would like to know why the shield is not allowed to rotate some
The only force that can make it rotate is the moving grease Is that enough to make it rotate enough that it can harm ??
But if you want to lock it in place I would try to eighter mill or gring a small notch in the outerrace and then stem the edge of the shield in that notch
But a strong enough person can get it rotating anyhow

Peter

As Gordon H says a zz(double shield) does not contact the inner race,it is not a seal.The shield is staked in place in a groove in the outer race and does not move relative to the outer race.I have never seen it any other way on any mfgs bearings(talking about mfgs that use ZZ to designate shields).I have replaced enough trashed shielded bearings that the shields were still crimped in place even after the balls and inner race were gone.
There is nothing new about how bearings work.You can call SKF or any manufacturer(not the vendor)tell them your problem and they can tell you any thing you need know.Now if you have bought some cheap no name junk all bets are off.
I have to admit I have never tried to see if the shields were loose,except when I need an open bearing and they have always been tight to pry out.Now if someone decides that a ZZ bearing needs to be lubed they can blow the shields(or seals ) out depending on the type of housing.If you need flush lubeing then you pull the shields out anyway.