Motor Rebuild - Questions

[Allan Speers]

I've decided to rebuild all of my older motors, just because.
They are typical 1 - 5 HP TEFC's, both 1 phase & 3 phase.

I have 4 questions:

1: What brand of bearing do you think is "the best?" I'm thinking NSK, unless there's a better option.

2: Where's a good place to buy such bearings, for a variety of older motors?
--------------------

3: When mounting the bearing on the shaft, do you recommend just a "dry" fit, as in using a little WD40 which will then evaporate off. Or do you recommend using some kind of compound, such as Loctite 641 bearing retainer?

4: This concerns the bearing beds. I've seen videos that recommend using a little molybdenum grease. Oddly, I've seen other videos that recommend using Loctite 609 bearing retainer! These two methods could not be further apart.
And some guys just lay them in there dry, after cleaning the beds with brake fluid.

What's the general consensus around here?

[Bill Dufour]

If the bearing fits are not worn no need for anything. Grease or oil will dry up and make removal harder. Do not do it unless you expect the internals to get badly rusted. The bearing retainer compounds are only used if the bore or shaft is badly worn so the bearing is no longer a good fit and you are worried it will spin and damage the motor.

You also need to remember that only one bearing, normaly the out put end, is locked into the bore or onto the shaft. The other bearing has to be a tight slip fit on the shaft or into the bore to allow for the motor shaft to expand as it heats up. If you glue both in place the bearings will quickly wear out from the thrust load.
Bil lD.

[Ron Selzer]

dry fit
3 phase is easy
1 phase the start equipment I am still struggling with getting back together without damage and working good
bearing supply house or ebay or Amazon, small bearings are fairly cheap

[Allan Speers]

If the bearing fits are not worn no need for anything. Grease or oil will dry up and make removal harder. Do not do it unless you expect the internals to get badly rusted. The bearing retainer compounds are only used if the bore or shaft is badly worn so the bearing is no longer a good fit and you are worried it will spin and damage the motor.

You also need to remember that only one bearing, normaly the out put end, is locked into the bore or onto the shaft. The other bearing has to be a tight slip fit on the shaft or into the bore to allow for the motor shaft to expand as it heats up. If you glue both in place the bearings will quickly wear out from the thrust load.
Bil lD.

Thanks, Bill

re the back end: I thought the idea was to leave a little room there and use a wave washer in the gap, which then compresses as the motor heats up.
I've never actually been inside a motor, but I've seen this is demo vids and some motor diagrams.

No?

[Richard Coers]

I guess you already have a hydraulic press, pullers and an array of pipe and mandrels to press bearings off and on? Never been inside a motor, but I've stayed at a Hoiliday Inn, right? LOL I was raised on a farm, "If it ain't broke......" is part of my credo.

[Bill Dufour]

Thanks, Bill

re the back end: I thought the idea was to leave a little room there and use a wave washer in the gap, which then compresses as the motor heats up.
I've never actually been inside a motor, but I've seen this is demo vids and some motor diagrams.

No?

On my Unisaw the arbor blade end bearing is locked in with a screw in bushing.. The shaft is thread with. alock nut sop it stays in place inside that bearing. On the other end that bearing is also held onto the shaft with a nut but the outer race is free to move in and out. If the bearing froze it would soon wallow out the bore in the arbor casting and make the saw scrap unless it could be rebored in a milling machine somehow.
I have also seen the wave washers or bellville washers used to keep the bearing from floating too much.
My old neighbor told me of a big generator that the bearing were too tight to turn under load so he had guys up on ladders loosen the bearing hold down bolts until it magnetically centered itself and started to run. Then they tightened them down in place.
Bil lD.

[Bill Dufour]

PVC pipe and couplers are good enough to make pushers to seat bearings. I split it length wise and make it smaller with a few hose clamps when needed. I aslo grind the inside of the old bearing a little so it is a easy slip fit, same with the outer race. Then I usually take it apart to use to install the new bearing. removing the old bearing usually destroys it anyway.
Bil lD.

[Bradley Gray]

"If it ain't broke......"

+1 on this.

[jared herbert]

A person can cause a lot of damage trying to fix something that doesn’t need to be fixed. Don’t ask me how I know this

[Bill Bukovec]

I ordered bearings for my lathe last year. They were only $20.00. They charged me another $20.00 for shipping. I had placed the order over the phone, so I didn't ask for a total, including shipping.

[David Kumm]

Most bearing manufacturers will make a little higher quality ABEC 3 bearing. Some call it an electric motor bearing, some use a different name. SKF Explorer and natchi Quest are two i know of. NSK, SKF, Natchi, are pretty similar in quality. A standard. motor bearing will usually have a C3 clearance to give the balls a little more room due to the bearing running in a warm environment. The ABEC 3 bearings will usually be standard clearance. SKF JEM bearings are C3. If the motor bearing also drives a spindle that needs low run out, like a direct drive unit or in a shaper, I always go go higher precision and tighter clearance. In a standard duty pulley application any decent bearing is fine. Odd brand or really cheap bearings are to be avoided but no need for Barden, FAG, Fafnir or other top end bearings. Dave

PS, if you don't have a press, use a small light bulb and heat the inner race and the bearing will slip on. No need for any Lock. tight unless the shaft is screwed up.

[Allan Speers]

Thanks, guys.

So is the consensus on the bearing beds to just dry fit?

[Frank Pratt]

Or the consensus is if it ain't broke, don't fix it

[Allan Speers]

And yet, I could really use an answer, since I firmly believe in preventative maintenance.

Esp when some motors are 30+ years old.



So?

[Jerry Bruette]

As long as the end bells of your motors are in good shape you don't need anything in them. You could use a little oil so the bearing slips in easier but there's no need for grease or any retainer.

If the bearings in the motors are 30 years old, why not replace them with the same brand bearing?

Better yet, if you have a few spare hours you could go the the SKF web sight and do some research on how to mount and install bearings. They'll show you what to look for in your end bells and on the journals of the shafts. They'll explain what's good and what's bad along with the proper nomenclature for parts and conditions and what to do to correct abnormal conditions.

Make sure to mark your end bells, motor casing and shaft with punch marks so you put it all back together in the proper order and place. I've seen motors that weren't marked put together backwards and when they were wired up would rotate in the wrong direction. Don't confuse Belleville washers with the wavy washers on the inboard bearings, they're two different creatures with different purposes.

Please don't drive yourself insane picking a bearing brand. I've taken apart brand new Baldor Gold motors that had two different brand bearings installed. NSK, Natchi, SKF, Fafnir, FAG are all very good brand name bearings that will all do what you want. I'd stay away from stuff from the local automotive parts store. Don't get all knotted up about the country of manufacture either. All of the above manufacturers have facilities around the world that make bearings to exacting specifications so your motor will run smoothly.