Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


decoding bearing part numbers

decoding bearing part numbers

decoding bearing part numbers

I have removed an koyo spherical roller bearing and have the numerical designation from the race however this really only tells the sizing and not several other features that different manufacturers encode differently from other manufacturers and from their earlier designations.

I'm looking for some cross reference repository that might make it easier for me to figure out what suffixes will suffice for my applications.

On some attributes, e.g. internal clearance, i have to guess because the manufacturers original selection is occluded in their part number approach which ignores the fact that they used a standard bearing.

these are double row spherical.. typical 21311 . The application is the lower end of an excavator swing box assembly so very low RPM service relatively little if any thrust but high lateral forces.

They operate in a bath of gear oil that also bathes the planetaries and there is (or was) a separate oil seal.

So the bearing doesn't need a seal or dust cover.

C3 or normal clearances are probably both OK.

Straight Bore.

One has an oil groove and the other doesn't. think that is probably optional.

Races are both steel which makes sense for the high lateral forces, although maybe with the lubrication, as long as they are in good shape it doesn't matter although my instinct is for steel in this application.

Not sure if i've missed any other relevant features.

So Koyo tells me their present RW33 designation has a brass outer race but RHW33 is steel. I've located an RW with and FY suffix. The picture doesn't look like a brass race but maybe it is chromed or . . . but maybe it is an older piece.

likewise SNR use EA while SKF used E.

If there is some quick tutorial somewhere on crossing these over including newer and older designations for the same manufacturer, I would be eternally grateful.


RE: decoding bearing part numbers

OK, got off the phone with Koyo and I misinterpreted what some salesman somewhere along the line said about brass. it's not a brass race, it's a brass cage.

Now I figure that doesn't make that much difference. The Koyo engineer said the steel cage is more common and that it is sometimes chosen on a cost basis.

But of course they are 10 times cautious about saying you should put in what you had. What difference does a brass cage make? I can't see it as a negative but maybe i'm overlooking something.

And on oil groove. He said some people think it weakens the outer cup although that shouldn't be the case as long as it is installed in a good round unmolested mount.


RE: decoding bearing part numbers

Spherical rollers rely on the bearing cage to keep the rollers in place. If you have significant thrust load present, the rollers will actually want to flip around and jam, and the cage is the only thing maintaining a stable orientation.

Brass cages are lower friction and more self-healing than a steel cage. Brass is considered the premium option but they do cost more. They both work but brass can work better. One past bearing salesman went so far as to proclaim that our bearing failures with steel cages would have gone away if we had only switched to brass, but I suspect he was mostly speaking to sound wise.

It's my personal perception that a brass cage makes sense when there is significant thrust, based on personal experience with bearing failures and cage wear due to thrust loading. I would therefore be less inclined to specify brass when there is predominantly radial load. Take that with a fairly large grain of salt since I've not worked with enough different spherical applications to pronounce my perception as a guideline.


RE: decoding bearing part numbers

so this confirms what i have sensed, that brass is the upgrade option. Whereas there is not significant thrust on these bearings there doesn 't seem to be a downside to brass. that's what i wanted to know because i have a brass cage bearing available.

it is C3 style. it does appear that folks are generally willing to exchange a normal and C3 bearing. I believe it is 15 thousandths additional internal clearance. maybe 40 vs. 25 thousandths. as best i can understand this is most apparent in the thrust play which isn't a big issue here.


RE: decoding bearing part numbers

and there is the question of the oil groove. talking to an engineer at koyo who said that some users/designers have an instinct that the oil groove weakens the outer cup. he seemed to be suggesting that , from his perspective, the oil groove was a non-issue insofar as bearing cup failure or cracking as long as the bearing was installed in a consistent unworn born.


RE: decoding bearing part numbers

I have not experienced SRB failures related to the W33 groove. So an unused oil groove is to me a non-issue.

The failure mode of the existing bearing should tell you something about whether these features are required in the replacement.


RE: decoding bearing part numbers

found this helpful chart but in conformity to murphy's law it does not include two manufacturers whose bearings i happen to be looking at at the moment, i.e., koyo and SNR. the table doesn't reproduce perfectly here but i think it is interpretable. I found it at: http://www.thisoldtractor.com/bearing_roller_beari...


Description NSK SKF Torr/FAF FAG
P/N Very Light 239xx 239xx 239xx 239xx
Light[/indent]230xx 230xx 230xx 230xx
Light, Wide 240xx 240xx 240xx 240xx
Medium[/indent]231xx 231xx 231xx 231xx
Medium, Wide 241xx 241xx 241xx 241xx
Heavy[/indent]222xx 222xx 222xx 222xx
Heavy, Wide 232xx 232xx 232xx 232xx
Extra Heavy 213xx 213xx 213xx 213xx
Extra Heavy, Wide 223xx 223xx 223xx 223xx
Suffix Bronze case, one piece, guide ring CAM,AM CA,CACM YM M
Bronze cage, two piece, guide flange M MC BR MB
Steel cage, two piece, guide ring C,CD CJ,CC CJ, VJ BLANK
Polyamide cage, two piece H -- VCF TVPB
Tapered bore 1:12 K K K K
Tapered bore 1:30 K30 K30 K K30
Carburized steel, complete bearing g ECD W40 W209
Carburized steel, inner ring only g3 ECB W401 W209B
Lube groove & holes outer ring E4 W33 W33 S
Lube groove & holes outer ring, holes inner ring E7 W513 W33W94 Sheading0AB
Holes only outer ring E3 W20 W20 SY
Holes only inner ring E5 W26 W94 heading0AB
No relube features BLANK BLANK BLANK --
Plugs provided for outer ring holes E42 W77 W84 heading0
Combination W33, W4, W31 E4P53 W507 W33W4W31 --
Combination W33, W31 E4U22 W506 W33W31 --
Combination W33, W26, W31 E7U22 W509 W33W94W31 Sheading0A
Outer ring w/extra close running accuracy P52 C04 C04 T52BN
Inner ring w/extra close running accuracy P53 C02 C02 T52BE
Inner & outer ring w/extra close running accuracy P55 C08 C08 T52BW
Special inspection measures U22 W31 W31 --
Inner ring & outer ring heat stabilized to 200°C S11 S1 -- --
Tight clearance C2 C2 C2 C2
Loose clearance C3 C3 C3 C3
Extra loose clearance C4 C4 C4 C4

RE: decoding bearing part numbers

The excavator manufacturer is likely the best source for accurate interchange information, though you may have to social engineer it out of them.

The problem with reading the bearing itself is that an OEM might buy a bearing with a bizarre array of options, which will be indicated somehow on the packaging for the OEM bearing or on related documentation, but no one has a strong incentive to encode that information on the bearing itself, so it may not happen.

Mike Halloran
Pembroke Pines, FL, USA

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close