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Cause of this wear pattern in taper roller bearing

Cause of this wear pattern in taper roller bearing

Cause of this wear pattern in taper roller bearing

I recently purchased a 1944 Monarch 16" CY lathe and I discovered a bearing in it with the wear pattern below.

What are the likely causes of such wear? Vibration and inadequate preload when the bearings have no relative motion?

Upon disassembly the bearing was full of a thick, tar-like amalgamation of old grease and appeared to have not been lubricated regularly.

FWIW, the lathe has a drive clutch. When the lathe is performing work, the clutch is transmitting power and the bearings are not spinning. When the lathe is idle, the clutch is open and the bearings spin at ~1,000rpm. The bearing is a Timken 368/324A taper roller bearings. It's partner in the bearing pair has no unusual wear pattern.

RE: Cause of this wear pattern in taper roller bearing

What happens is that heavy items like this stop being used and sit on a factory floor while other equipment with similar harmonics are still being used. This causes the not-used bearings to take a pounding just like that. I've read of similar failures in back-up fans where one or more other fans are used constantly. Come a failure and the backup, which may start just fine and is assumed to be in factory fresh condition, soon fails because it's bearings have been beaten like this. The fact the lube is gummy says it's been parked a very long time, long enough for the oil to creep out, maybe 10 years??

I would expect a new bearing to be fine in this lathe for a long time as long as it gets used and/or is not exposed to heavy vibration.

Edit - I remembered it was fan units, not generators; still rotating equipment that's not rotating while out of use.

RE: Cause of this wear pattern in taper roller bearing

Looks like false brinelling damage, which is a type of fretting. Caused by cyclic relative axial sliding at the roller/race surface contacts while the bearing is stationary or oscillating at very small angles of rotation. Lack of lubrication at the roller/race contacts significantly contributes to this type of failure.


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