Bearing Issue...Never Seen This Before...

[michael.kitko]

We have this bearing that failed at my place of work. As you can see, it kind of looks like fluting, but this is the outer housing for the bearing to sit in, not the bearing race, which is where I would expect to see fluting. When it was put in, the bearing had a .002" interference fit and now it measures +.003". The bearing that came out, rotated freely and smoothly by hand. This housing was installed three days before this as a brand new install before it got pulled for an unrelated issue. I am just wondering if anyone has seen this and if so, what caused this wear in this area? Thank you in advance.

 

[Joe Gwinn]

We have this bearing that failed at my place of work. As you can see, it kind of looks like fluting, but this is the outer housing for the bearing to sit in, not the bearing race, which is where I would expect to see fluting. When it was put in, the bearing had a .002" interference fit and now it measures +.003". The bearing that came out, rotated freely and smoothly by hand. This housing was installed three days before this as a brand new install before it got pulled for an unrelated issue. I am just wondering if anyone has seen this and if so, what caused this wear in this area? Thank you in advance.

I've seen that kind of pattern in the fault-analysis rogues galleries from bearing manufacturers. As I recall, that pattern is due to the outer race rolling around bouncing within the slightly oversize seat in the housing. No way was that outer race pressed in with 0.002 inch of interference, no matter what the drawing or procedure said. By the way, what is the diameter of the outer race?

See also posting #8.

 

[Gearclash]

That looks like a machine tool chatter pattern . . . ??

 

[eKretz]

I'm with Joe. I don't see any way that it could have been a real .002" interference fit and come loose like that. The caveat being that someone didn't thoroughly measure for deviations from cylindrical shape and roundness and it didn't actually have that .002" interference fit across the whole diameter. Did *you* actually measure it before the bearing was installed? Or are you relying on someone else for this info? Also, what did the OD of the bearing look like, any photos of that?

To be honest, due to the irregular pattern of the markings, this looks like a housing that was bored with chatter to me. And was slightly oversized from the start due to that.

 

[guythatbrews]

There is even chatter in the retaining ring groove. Pretty clear it was a bad turning job.

 

[gbent]

That ol' gal sang big time when in the lathe. Way to much spindle speed for limited feed rate.

 

[guythatbrews]

For we older gents.

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[Joe Gwinn]

There is even chatter in the retaining ring groove. Pretty clear it was a bad turning job.

I looked through the SKF failure photos. What I was thinking of is called "ring creep due to inadequate fitting" (meaning too loose), but none looked like the photo in posting #1.

And the bit about seeing the pattern even in the snap-ring groove supports the chatter theory.

 

[BT Fabrication]

100% that is machine tool marks and someone screwed up and oversized it.

 

[mottrhed]

That's not from a bearing, but out of curiosity what kind of bearing goes in there? I presume a cup/cone if you were shooting for a .002 interference? Either way with the thin wall, a .002 interference probably isn't real once installed as the housing likely swells.

 

[kevin66]

Looks like chatter on the finish pass. Just by what I see in the photo I don't think the bore grew by any wear from a spinning outer race since you can still clearly see where the boring bar was retracted at size leaving a witness mark on the way out of the bore.

 

[Farmer Phil]

Find out where that interference went.

It'll be fine though, use some green loctite retaining compound and all will be well.

 

[Ralph_P]

The .002" press fit was on the peaks of the chatter marks.

 

[Lewie]

For we older gents.

Kate Smith Sings God Bless America, Movie Short From 1943 on Make a GIF

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makeagif.com

Should have had a 48 star flag in that video. Brings back lots of memories . :-)
...lewie...

 

[Freedommachine]

Find out where that interference went.

It'll be fine though, use some green loctite retaining compound and all will be well.

Spoken like a true farmer . I agree, green loctite and on to the next job.

 

[Limy Sami]

The .002" press fit was on the peaks of the chatter marks.

Either that or the hole was oval, or maybe trilobal from chuck jaw pressure, when it was gauged.

 

[michael.kitko]

Thank you all for the answers.
1. I watched them fit the bearing and it looked like it was going in like always. I never saw the inside of this one before we fit it.
2. The chatter theory could be correct given that the machine shop they use constantly has wrong dimensions. In fact, the other five of these had wire edges at the bottom facing up.
3. It's a double roller bearing from SKF.

 

[boslab]

Best guess is a heat treatment fault though metallurgical inconsistency could be in the mix, the trading standards folk have caught loads of fake skf bearings up to giant ones, they are all correctly stamped etc but fail, guess where they come from
Mark

 

[Stirling]

What kind of load is on it?
Belt pulling/loading in one direction, swinging force (vibratory motor?)
I’ve seen housings grow due to load when the wall was too thin or the surface finish too rough (high feel hills/vallys or chatter)
Looking at the finish I’m leaning on the chatter theory.

Another consideration, was it pressed it or was the housing heated to allow it to drop in?
Again with high peaks and valleys pressing in can smooth out the peak tops and you’ll suddenly have a different size.
I used to to LOTS of endbells sleeve repair and we always heated the housing to drop I the sleeve for a stronger bond.
Easa associations literature states it was something like 8 times better hold when a sleeve was placed in w/heat/cold vs pushed levelling out all the peaks and valleys

 

[michael.kitko]

This was on the non-drive side. I did do thermal shots of the housings while they were running on the other housings and noticed that the material these are made out of hold heat a lot better than the aluminum ones these are replacing. I'm personally leaning toward them having a pre-existing chatter in them and the techs that installed the bearings didn't catch it before installation.