Perfect Example of Cutting Wear

[M.D. Holloway]

Someone sent me a sample of some crap they dug out of a bearing. The bearing is a self-aligning tapered roller bearing. The have not done a very good job installing it correctly even though these bearings are a bit more forgiving than most. They also didn't do a very good job at keeping up with their greasing frequencies.

All that said, took some of the junk, rinsed with heptane, filtered out the fines and put a magnet to the stuff left over. This is what I pulled out - a perfect example of what is known at cutting wear which is caused by the cutting in of debris (typically wear debris) and gouges out this strip of metal. Occurs mostly in under-lubricated bearings with previous wear debris from spall particles or in limited scenarios fatigue propagation.


This is the type of thing that I am going to use in my next book "The Wear Debris Encyclopedia". For real!

[masraum]

So is that scale accurate? THat's a pretty big bit of debris.

[M.D. Holloway]

Yup - cutting wear debris can be good size relative to other types of particles - the shavings can be as thin as 0.2mm. Think of the shavings you get when you gouge out wood bits, not that much different. I have actually seen larger.

[RWebb]

looks like it was peeled off by a beginner on a lathe!

[Joeaksa]

Thats not debris, thats CHUM!

Damm thats big! Bearing never had a chance!

[sammyg2]

Originally Posted by RWebb

looks like it was peeled off by a beginner on a lathe!

That was my first instinct, that it was left over after the machining process and someone did a piss-por job of cleaning out the housing.
This was on a pillow-block bearing, right?

[lane912]

lubrication good-

[sammyg2]

I've been looking at it some more and can't see where that metal could have come from.
Certainly not from the races, they are way too hard and brittle.
Not from the housing because they are typically cast iron and turn to powder when exposed to excessive friction.
It's possible it had a stamped steel cage instead of bronze but I've never seen one wear like that at all. Not even close.
The shaft seals are usually soft aluminium or bronze, no go there.

The only thing I can think of (and it's a long shot) is often these bearings are often mounted on a tapered sleeve that fits over the shaft. The ID of the inner race has a matching taper and when an SKF nut on the sleeve is tightened, the bearing is pushed up the sleeve onto the taper. They call that a taper lock for some reason, go figure
Anywho, if it failed catastrophically that metal could have come from the nut or the locking washer behind the nut. Still a long shot, it'd have to an ugly crash.

I'm still kinda leaning towards that metal shaving from a lathe theory.

DISCLAIMER: iffn this is some unusual type of bearing application and isn't a pillow-block or flanged bearing, all bets are off

[RWebb]

was it a Chinese bearing?

Mexican?

Ugandan?

[M.D. Holloway]

Sammy, your logic is sound but as far as I can tell - unless there happens to be zero in the way of QC/QA in bearing companies these days, this came from the race with some pieces from the rolling elements. Atomic Absorption proved out the metallurgy. I have seen it a dozen or so times. Go figuer right? The more you look, the more you see. It is amazing what will occur and just what is allowed.