Motor Bearing replacement

cooncatbob · Nov 4, 2010

A few months ago I replaced the original Dayton 1/2 hp drip proof motor with a
1/2 hp WEG TEFC motor that I bought NOS off e-bay.
Recently I've developed what at first I thought was a drive train noise, but I've isolated it to the bearing on the pulley end of the motor.
When I lessen the tension on the vee-belt the noise lessened but I'm afraid it will eventually get worse and fail.
I've used a probe stethoscope and the noise is definitely coming from the bearing.
How difficult is it to change the bearing?
It looks like I can take the fan cover off, undo the 4 long bolts, remove the pulley and the end of the motor housing with the offending bearing.
How difficult is the bearing to remove from the housing?
I live in Sacramento, CA. and there's a bearing supply place in the phone book.

bigmac · Nov 4, 2010

Bob, If the bearing is situated down in a recess it can be a bugger unless you can get a pin drift to catch the outer race from the outside of the end bell. Driving on the inner race may or may not do it. If you have a motor repair shop nearby, I would take them the end bell & have them replace the bearing. They have fancy pullers for that. I'm sure a replacement is not very expensive.

jhruska · Nov 4, 2010

Remove the fan shroud/cover. Remove the fan. Remove both covers. Pull out the armature. The bearings will likely stay on the shaft.
Hard part, maybe, is bearing removal. A puller in combination with a bearing back-up, back-up plate, would work well.
Installation is a press fit. Use a piece of pipe for installation. Clearance to the shaft and longer than the shaft of course. If the motor shaft is .625, make a washer that has a bore size of .630 +.005. Make a step in the face so the washer only contacts the inner race of the new bearing. Put the washer between the pipe and the bearing, add
never-sieze, drive the bearing into location.
Before removing the old bearing, mark the location of the inner side for reference.
Regards,
John

Is that a spliced serpentine belt?

Clive603 · Nov 4, 2010

When you get a new bearing make sure that they are suitable for electric motor duties. No idea what the difference is relative to a generic bearing of the same number but I do know of people who have gone the generic route and been rewarded with premature failure after a short life. This was over a decade ago before low cost and no-proper-name imports were prevalent.

Clive

knudsen · Nov 4, 2010

Beat that sucker! When you beat it back on the shaft, be sure and beat on the inner race only. Beating the outer race will damage the bearing. A socket that slips over the shaft and applies the beating to the inner race only makes for a happy bearing in the end.

cooncatbob · Nov 4, 2010

jhruska said:
Remove the fan shroud/cover. Remove the fan. Remove both covers. Pull out the armature. The bearings will likely stay on the shaft.
Hard part, maybe, is bearing removal. A puller in combination with a bearing back-up, back-up plate, would work well.
Installation is a press fit. Use a piece of pipe for installation. Clearance to the shaft and longer than the shaft of course. If the motor shaft is .625, make a washer that has a bore size of .630 +.005. Make a step in the face so the washer only contacts the inner race of the new bearing. Put the washer between the pipe and the bearing, add
never-sieze, drive the bearing into location.
Before removing the old bearing, mark the location of the inner side for reference.
Regards,
John

Is that a spliced serpentine belt?

No, the belt's 1 piece, I installed it when I refurbished the lathe.

jhruska · Nov 4, 2010

A 'motor quality' bearing will be quieter than the same size bearing from the same manufacturer.

"In the aftermarket, SKF uses the designation 'JEM' for deep groove ball bearings that are used in electric motor applications. The 'J' designates a pressed steel cage and 'EM' designates electric motor quality as required by electric motor OEMs."

in quotes from SKF Product Guide

The motor is TEFC so a shielded bearing is suitable. I like the seals for keeping the grease in the bearing. The seal will not add any appreciable drag to the motor.

John

cooncatbob · Nov 4, 2010

Got the motor apart, it was quite easy, hardest part was the bottom back screw on the fan cover.

Both bearing spin quite freely, but the bearing on the pulley side was only making noise when it was under tension from the vee belt.
The offending bearing on the left is in backwards so I can't read the numbers on it.
The bearing on the fan side says KBC, Korea, 6202Z.
I'm goint to take it down to the local motor shop and have them remove and install the new bearings.
The fan side bearing had the wavy spring washer in the pocket but there wasn't a washer in the pocket on the pulley end, should there have been?

atomarc · Nov 4, 2010

No...there is only one wave washer typically, it just loads the armature and bearings a bit. I don't know if this motor was sold to you as 'new' but be sure to look at the bearing pocket in the end bell on the output shaft side. It isn't uncommon at all for this fit to go to hell...usually not in a new motor though.

Stuart

Newman109 · Nov 4, 2010

6202Z is a common bearing. There are many of them available inexpensively on eBay.

6202Z bearing items - Get great deals on Business Industrial, eBay Motors items on eBay.com!

jhruska · Nov 4, 2010

Right on Stuart, only one wavy spring washer.

I would request a non KBC bearing. SKF/Fafnir sources bearings from all over the world but the quality is there.

That 6202 aka 202 bearing is pretty common.

SKF 6202 2Z JEM Two shields motor quality, very common and should be on the shelf.
or
SKF 6202 2RS1 JEM Two seals motor quality.

How does the lathe run with the serpentine belt compared to a flat belt?

John

cooncatbob · Nov 4, 2010

jhruska said:
Right on Stuart, only one wavy spring washer.

I would request a non KBC bearing. SKF/Fafnir sources bearings from all over the world but the quality is there.

That 6202 aka 202 bearing is pretty common.

SKF 6202 2Z JEM Two shields motor quality, very common and should be on the shelf.
or
SKF 6202 2RS1 JEM Two seals motor quality.

How does the lathe run with the serpentine belt compared to a flat belt?

John

The leather belt was rotten when I bought the lathe so when I refurbished it with the help of the folks on this site I went with a Goodyear Poly Vee belt that I got from McMaster.
I've never used a lathe with a leather belt, I've had no problems with this belt in 4 years on use.

cooncatbob · Nov 4, 2010

atomarc said:
No...there is only one wave washer typically, it just loads the armature and bearings a bit. I don't know if this motor was sold to you as 'new' but be sure to look at the bearing pocket in the end bell on the output shaft side. It isn't uncommon at all for this fit to go to hell...usually not in a new motor though.

Stuart

The Fit is actually quite good.
I've cleaned both pockets with a fine gray scotch-brite pad and the bearings fit into the pockets firmly.
I changed my mind and pulled the bearing off the myself, the 2nd larger bearing is Argentinian and I thinks it's a
6203z it's very hard to read.
I'm going to Bearing Engineering tomorrow for replacements.

cooncatbob · Nov 5, 2010

Mission accomplished.
Went to the bearing store today and purchased the 2 bearings for my motor, the pulley end bearing was 62032z and the fan end bearing was 62022z.
The smaller bearing was actually $1.40 more then the small one.
Total plus tax was $19.60.
They're both SKF JEM bearings.
Installation was a breeze, took about an hour to get everything back together, once again the hardest part was the back bottom screw on the fan cover.
Even though I've got a mini off set racketing screwdriver it was a pain.
Motor's is quite even under belt tension.
I wonder whats wrong with the original bearing, flat spotted ball, cage coming apart?
It was quite without the belt but once you installed the belt under tension it would start making noise like gears that weren't meshing, that why I thought it was the gear train on the lathe at first.

Clive603 · Nov 5, 2010

I'd vote for the original bearings not being motor quality. The quiet off-load, bad gear sound under belt tension is a good description of what I heard when helping diagnose early failure of generic replacements.

Clive

k3vyl · Nov 6, 2010

Ball bearings

The structure of the bearing has simelarity to a gear only it has balls instead of teeth.The sounds made by those structures are also simelar.The fellas that do the vibration analysis can tell you how many balls a bearing has in it while its running by looking at the screen of the analyser.

knudsen · Nov 6, 2010

I wonder whats wrong with the original bearing, flat spotted ball, cage coming apart?

It didn't like the side load.

jhruska · Nov 6, 2010

I wonder whats wrong with the original bearing, flat spotted ball, cage coming apart?
It was quite without the belt but once you installed the belt under tension it would start making noise like gears that weren't meshing, that why I thought it was the gear train on the lathe at first.[/QUOTE]

Check to see if the motor pulley and the driven pulley are parallel. A side load will pull the ball bearings against the wall of the groove. A deep groove bearing can carry a substantial radial load but only a minimal side load.
John

cooncatbob · Nov 6, 2010

jhruska said:
I wonder whats wrong with the original bearing, flat spotted ball, cage coming apart?
It was quite without the belt but once you installed the belt under tension it would start making noise like gears that weren't meshing, that why I thought it was the gear train on the lathe at first.

Check to see if the motor pulley and the driven pulley are parallel. A side load will pull the ball bearings against the wall of the groove. A deep groove bearing can carry a substantial radial load but only a minimal side load.
John[/QUOTE]

Yipes!
Put a 24 inch level across the big pulley to the motor and my motor was canted about 1/8 inch.
Loosen the motor bolts and square everything up.

tribologist · Nov 6, 2010

The wave washer gives some axial preload that ensures that you dont get skidding in the bearing and it also makes it run with a higher contact angle. When you load it up with the belt it will run with a small contact angle. You might have damage on the races outside where you ran unloaded.

I dont think it is correct to claim that the Motor Grade bearings are at higher quality or designed for longer life. The designation is there to guide people what type of bearing to use. Typically motors use pressed steel cage to limit the risk of a trashed motor from an overheated bearing. It is also common to use filtered long life grease to reduce noise and C3 clearance since the rotor is often running warmer than the end bell resulting in reduced clearance when running.

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