Motor bearing lube question

One of my machines has a 3 HP GE induction 213 frame motor. There is a threaded hole plugged with a slotted plug that looks like it could accept a zerk fitting at both shafts. In general is this indicative of sealed non service type bearings..........Thanks..........Bob

The older the motor the less chance of anything. My method is to open the motor to be sure.

Other folk might do this if there is a threaded hole on both the high and low points of the bearing housing:
- pump grease into the top hole and expect that the old grease is going to come out the bottom hole.

You really have to open the motor and examine the bearings. Those meant for lubrication-in-place will have a hole, and possibly a groove in the outer race. If just a hole, that has to be lined up with the port in the end bell casting. I've seen installations where the bearing side facing the end bell is open and the grease enters there instead of from around the outer race.

There often is no 'exit' hole for old grease. You just have to be careful not to over-lube.

In either case, the bearings are 'shielded' and not 'sealed'. Of course, you don't want to replace such with sealed bearings because the seals will be blown out when grease is injected.

I'm not an electric motor expert. These comments are from my own experience over several decades.

Thanks guys. I hoped there would be a definitive answer but I think you are correct. Only way to know for sure is to disassemble it. The plugs look to be OEM. I pulled the plugs and can see evidence of grease but the holes are not filled with it at all so it's never been user greased.
The motor is from the 60's but almost no time on it.
I'm thinking if it's not broke I won't fix it. If it gets noisy I'll knock it apart. Thanks........Bob

My 7.5 hp Baldor motor is used as an idler in an RPC. It had Zerk plugs in a hole over each bearing. The motor was new old stock when I got it and was noisy and overheated after some 15 minutes at first.

I disassembled it and discovered that it had open precision roller bearings on each end. They were caked with old, dried grease.

Some research on the Baldor website said that the proper grease was Mobil PolyRex EM. It's blue and comes in a tube. I bought a tube on Amazon and, after cleaning out the grease passages and lubricating the bearings and plugging the holes with small hex plugs, I reassembled the motor using PolyRex grease. It now runs quietly with no overheating.

Since the motor has open bearings, any excess grease would have gone directly into the windings with disastrous results.

Baldor says that the PolyRex is good for 1,000 hours between re-greasing. I added a Hobbs meter and I'm up to 200 hours or so now with no problems.

I

Newman109 said:

Since the motor has open bearings, any excess grease would have gone directly into the windings with disastrous results.

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The right way would be to have the bearing open or with a metal shield with holes on the end bell side and a rubber seal on the rotor side.

rons said:

The right way would be to have the bearing open or with a metal shield with holes on the end bell side and a rubber seal on the rotor side.

Click to expand...

In the case of my Baldor motor, it was wide open inside. Although there was a slinger on each side of the rotor, any excess grease pumped into the original grease fittings would have gone directly onto the rotor on each side.

Here you can see the grease fittings before I cleaned out the motor and plugged the holes.

bhigdog said:

Thanks guys. I hoped there would be a definitive answer but I think you are correct. Only way to know for sure is to disassemble it. The plugs look to be OEM. I pulled the plugs and can see evidence of grease but the holes are not filled with it at all so it's never been user greased.
The motor is from the 60's but almost no time on it.
I'm thinking if it's not broke I won't fix it. If it gets noisy I'll knock it apart. Thanks........Bob

Click to expand...

I had a similar situation with a motor on a surface grinder. I did regularly put a zerk in the hole and a pump of grease, but unfortunately in time the bearing still started to make noise. I removed the motor and disassembled it to find the original greasable bearing had been replaced by a permanently lubed sealed bearing. I replaced the bearing(s) with the same permanently lubricated style and made a note in the maintenance file that the plugs should remain in the holes and that no lubrication was required. It's been over 5 years since the bearings were replaced and the machine runs fine.

Here's my take away. The motor on my LeBlond lathe also has threaded plugs. The spec plate actually lists the bearing #. The number indicates that the bearings are sealed bearings. So I'm of the opinion that motor makers used a variety of bearings depending on application and used a common end casting with either a fitting or plug as needed. I'm going to stick with my plan to just run the motor and if it gets noisy I'll pull it apart. No use trying to fix it if it isn't broken and fixing (greasing) it may break it............Thanks all.........Bob

They are installed as sealed by Baldor. They are giving the customer choices during the life span of the motor. Life span may depend on choice taken.

Pry out the rubber seals on the outside bearing races and leave the inside seals alone. Now the lube holes can be used. So, one day in the future you can do this
and add new grease to extend the original bearing usage.

Buy new bearings and be sure. You still have the choice of rubber seals on both sides or one side sealed and the other not.

Wait for noise and then do something.