Bearings

[TreefarmerNN]

Partly as a response to Jeff's challenge to start a new topic and partly because we just had to rebuild a drum mower, I'll throw out this question.

At what point is an upgraded bearing worth the extra cost?

Example- ou rmower needed multiple bearings but I'll just talk about one.  It's a 6209 RS2.  Basically a metric bearing, nothing really extreme.

I can get bearings costing from $20 to $160.  The $20 bearing is Chinese (of course).  American made bearings start at $33 and go up from there.  It all fairness, the very high cost ones are special bearings- advertising either high speed or ultralow drag or multiple special features.

Where do you call "good enough" on bearings?  What factors enter into the buying decision?

[TroyC]

If it is a job I do not want to do over anytime soon or if it is a critical area, I use Timkens most of the time. Looks like yours is a double sealed ball bearing and it is about 34.00 on Amzon. You can probably find it locally for a lot more.

[rusticretreater]

Of course it depends on the application, but most of the time I opt for the better or best version.  I invest for the long run.  Everything I have is seasoned and broken in.  Including me.

[beenthere]

As TroyC stated well, if it is a job to replace (and most of them are), then for me I'll go with some extra expense to get a bearing that I think will last the longest time. So for me, it is a no-brainer.
I'm happy to get the bearing needed, and just like buying oil, get the best.
Same with lawn mowers..

My 1999 Deere diesel mower, mows average of 3 hours a week every summer.. 

[Magicman]

Since I don't have a "bearing store" my loss is not the replacing time, but the shipping time.  I try to opt for the best bearings possible to reduce the replacement instances.

[GAB]

Just as important as the bearing is the grease that you use on those that are greaseable.  Like one of my brothers said since I started buying and using the more expensive grease I have chaged a lot fewer bearings.  
GAB

[YellowHammer]

I would not get a $160 bearing unless it was on the propeller shaft of my airplane.  I've worked with several bearing companies, and most of the time, once you get above the Econ grade, the bearings have just been lot tested and had fit to achieve a higher running class and precision, although they all come from the same batch.

For example, I had to order some very precise shaft bearings to rebuild an Allison/Rolls Royce turbine engine for a cruise missile, running with shaft speeds of 43,000 RPM and slightly over 220 degrees.  I called Barden Bearing, they said they had lots coming out, 500 batches of inner and outer races and they would not know how many they would have to sell to me until they hand assembled them.  So I asked what do you do with all the "not highest spec" running class parts, and they said they simply sort them by lots, based on their dimensional tolerances, and these are the ones they sell as "consumer" or "commercial" bearings.  When they were done, they only had 12 bearings that assembled to my engines specs, but they had lots of consumer bearings.  Well, I needed 20 bearings, so I simple told them to send me another dozen of the consumer grade, and when the test program was over, it was hard to tell the difference in the performance or life of each compared to each other. 

So the point is, go to a good bearing manaufacturer (not India) or to any company that is an ISO QMS approved company, and buy the standard consumer grade bearing rated for the application, and you will generally be fine.

The seal material (elastomer) will be the issue on a sealed bearing, as well as corrosion.  That's what kills a bearing (unless it's just a garbage bearing).  The materials used in them are very susceptible to corrosion, it gets in the grains of the metal, and the crack runs and crunch, it's over.  So as said in an earlier post, use the best oil or grease possible, that is what will generally fails a bearing, running dry, leaking seals, and poor lubricaiton. 
Just my 2 cents...
         

[TreefarmerNN]

Another question for everyone.  One failed bearing had the outer race split into two rings.  This bearing was in a casting.  I'd never seen a bearing fail like that but on inspecting the casting it appeared that possibly during installation the bearing was cocked as there was a smear on the casting.  My guess was installation was via the inner race and when the outer race split it was just pushed into place even though the race was broken.  In one sense, that worked as we ran the mower for a few years before things went downhill.

Does this seem likely?  I can't show pix as I've polished out the smear and put it back together.

Thanks.

[scsmith42]

Typically I source bearings from a reputable supply company.  Brands include Timken, SKF, Fafnir, Nachi, Bower/BCA, etc.  

Bearings for the roller guides on Tom the Baker Sawmill are sourced directly from Cooks, as they have a special groove cut in them to allow grease to enter the race area.

I try to stay away from non-major brand Chinese bearings whenever possible.

[Ron Wenrich]

Before the Chinese stuff, there was the Japanese bearings and chain.  The cost savings are in the elimination of downtime.  We found that US made chain and bearings were a cost savings in the long run.  You can't go by an item's cost.  You have to look at the associated costs.

[TreefarmerNN]

I've got the Timken bearings on order.  The cost difference is a significant percentage but not a huge dollar difference. 

Funny, we've got a baler that most of the main bearings have instructions to grease ONCE per season and only one or two shots of grease at that.  They've been running for 50 years so I guess the people knew what they were talking about. 

[hardtailjohn]

Just as important as the bearing is the grease that you use on those that are greaseable.  Like one of my brothers said since I started buying and using the more expensive grease I have chaged a lot fewer bearings. 
GAB

Not only the quality of that grease, but the grade of it as well.  I've seen lots of problems, especially with heat, from running a #2 grease when it called for a #1 or #0.  It can shorten the life quickly.  We have a 6" diameter shaft on the main cross shaft of our rock crusher and it turns about 2500 rpm. When we were starting out, I ran a #2 grease all through the machine, and noticed that shaft running about 250 degrees consistently. Within a season, we failed all 4 roller bearings on it. When I replaced them, the guy I got my grease from, suggested a #1 grease. The temps dropped 50 to 75 degrees immediately, and they've been in there for 7 seasons so far.
JH

[Machinebuilder]

For use in a drum mower the standard 6209 2rs is fine.

it will be a loose enough internal clearance to not need special grease, it is a double sealed bearing so there is no way to grease it.

your theory about it cracking during installation is a good posibility, If so it was not a good bearing.

the best explanation I have heard about greasing bearings.

imagine running in mud do you want to run in ankle deep mud or knee deep mud.

Too much grease heats up and runs out. When working in High speed (5-10,000rpm) spindles you pack them 1/4 to 1/3 full.

I did watch a german fields service tech use a syringe and a scale to grease a bearing once...................