View Full Version : New bearings are too stiff

Black Forest
12-05-2012, 04:31 PM
I ordered new ball bearings for my little electric motor. They are 22mm OD. 8mm ID and 7mm wide. They are sealed on both sides. They are SKF brand. They seem very stiff and not so free turning. Do you think if I took the seals off they would turn a little more freely? I put the motor together and connected it to electricity but the motor won't start on its own. If I spin the squirrel cage it will run but not up to top speed. I even mounted the motor shaft in my electric drill and spun the motor with the drill to see if they would loosen up some. That didn't help.

I hope JTeirs doesn't see this thread because I didn't send it to him for approval before I posted. I didn't think a picture of a normal bearing was necessary.

12-05-2012, 04:35 PM
They will. That's why most electric motor bearings have shields, not seals. On a larger motor they will wear-in rapidly and usually be ok. You can can get non-contacting labyrinth seals for such use.

John Stevenson
12-05-2012, 04:37 PM
In friction critical or high speed applications buy ****ZZ bearings instead of ****2RS.

The RS [ Rubber seals ] are in contact with inner and outer races hence friction.

The ZZ's have a tiny gap between the tin shield and the inner so no contact and less friction.

12-05-2012, 04:42 PM
If you want seals, the non-contacting labyrinth seals often have the VV suffix, but this can be manf specific.

12-05-2012, 04:46 PM
I believe you replaced the original bronze bushes in a shaded pole fan motor?

Those bushes are often self-aligning to cope with issues in the cheaply stamped frame.

A long shot, but maybe the stiff new bearings are also slightly skewed ? As you've found, the start torque of a small shaded pole motor is pretty low.



Black Forest
12-05-2012, 04:49 PM
So is it not a good idea to take the seals out of the bearings I have? Only because it takes a while to get the shielded bearings delivered to me and I need my fan! I will order different bearings but for the next week it would be good if the fan was working.

12-05-2012, 04:52 PM
Go to the sport store and buy some skate bearings. I think these are 608 size as well and have shields. They usually come in packs of 8 or 16 so you have some spare ones. The price is a LOT better than at the distributor for single bearings. You can even still buy SKF as they have a special sports line.
If you do want better sealing than the metal shields, get the 608-2RSL, these have low friction seals and are suitable for high speed as well.


12-05-2012, 06:33 PM
Just a thought, if your original bearings didn't have seals why would you need them? Take them off and see if things improve. If not you have another issue but have lost nothing because the original design, that ran for many hundreds, perhaps thousands of hours had no seals.

12-05-2012, 06:41 PM
Yes, you can pry the seals out and the bearing will then have very low friction. Without seals or shields, you risk getting dirt in them- that's the only drawback. Pry them out and instal the bearings- put it all together and get on with drinking coffee!

Peter S
12-05-2012, 07:27 PM
It is risky quoting bearing seal terminology because it varies between makers. In general terms, rubber 'seals' are available in two types - contact and non-contact. A true contact seal is noticably stiffer to turn (and probably different max speed).

E.g. in NTN terminology Z (ZZ) is shield, LB (LLB) is non-contact rubber, LU (LLU) double lip contact rubber.

A.K. Boomer
12-05-2012, 09:10 PM
there's also a drag factor with copious amounts of new thick grease that has to be churned - it can actually be so great that it will pop the seals right out of them at high RPM's....

12-05-2012, 09:28 PM
Have you burped the bearing? Take a pick a just do break the seal loose. The bearing will make a very faint noise or "burp" and will rotate much more freely afterwards.

12-05-2012, 09:38 PM
Using a soft-faced mallet or a block of wood and a hammer, strike the ends of the shafts and the end bells while the motor is running. The idea is to get a race to move in its bore enough to unload the residual stresses that can remain after drawing the end bells on. This is perfectly normal on a motor that has bearing races that are not a slip fit in their bores.

A.K. Boomer
12-05-2012, 09:44 PM
Great suggestion...

J Tiers
12-05-2012, 11:44 PM
I saw it.....Too bad for you! Or maybe not.

Yes sealed have more friction, yes once the grease has "channeled", meaning has been pushed mostly out of the way, the bearings should be freer than they are now. But those fans are weak. Luckily, they are usually not harmed by running slower, most will not be damaged even if they jam up solid.

Since that is a fan, if you take off the seals, the bearings may very rapidly be gunked up with coffee dust and whatever else is in the air..... the fan pulls it over the motor usually..... unless this is a blower type and the air never gets to it.

In fact, I wonder if maybe the original bearings had dust around them. If so, that is very typical... the dust pulls out some of the oil, and more dust arrives, pulling out more oil. Pretty soon the bearings squeal.

You can often (or by now probably you could have) take the motor apart and re-oil the old bronze bearings with light oil. or maybe you don't need to take it apart, just let oil soak in overnight. I have some ventilation fans that need re-oiled 2x or more each summer, because we don't have air-conditioning here in St Louis, and the fan runs all night ever night in summer. Lots of dust gets on the shaft and sucks the oil out.

Even shielded might not last, if coffee dust can get in where the fan is. Sealed should be fine, if the motor can spin them.