# Does my lathe motor need bearings replaced?



## ErichKeane (Dec 20, 2019)

I have a big old lathe with a 15HP 3 phase 3450 RPM Baldor motor.  It weighs ~300 lbs, so I'm in no hurry to try to get it out of the foot of my lathe or moved around at all  

It seems to work 'fine'.  It isn't particularly noisy or anything.  When starting up, there is a brief 'rattling' sound (that could potentially be something else on the lathe?) at about 30-40 hz, but it goes away at 60 hz.

However, when i went to do some stuff to it, I discovered that the shaft doesn't seem 'attached'.  I smacked it with a mallet, and it moves ~1/2" inward, then comes back.  It seems to only be held in place by the magnets itself, as it does the little 'shimmy' back and forth until its in the right place.  In my head, this means it needed bearings a few decades ago (as in, the bearings are just so bad they basically don't exist).

However, I'm hopeful that this is just the design of some motors?  Is it possible that it is a bearingless motor?


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## JimDawson (Dec 20, 2019)

That motor does have bearings in it.  I'm not sure why there is that much end play, maybe the bearings are a bit loose in the housing, but I wouldn't concider that to be serious.  If the bearings were really bad or gone, the motor would be making a lot of noise when the armature was rubbing on the field segments.

Also not sure why it reacts that way when you smack it with a mallet, it may be spring loaded on both ends.  There are no magnets in that motor unless it's a DC motor.


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## ErichKeane (Dec 20, 2019)

Hmm... interesting.  Thanks for the feedback!  I definitely don't have any obvious rubbing or play up/down, but I was putting a pulley on it and was fighting against it running away as I was smacking at it.  I've never heard of a spring loaded shaft before!

It seems to work and is reasonably quiet (at least as far as I can tell...) so I'm less concerned, but looking at the replacement costs for something like this is pretty frightening!


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## JimDawson (Dec 20, 2019)

I put new bearings in my 15 HP Baldor, I think it was about $25 for the two bearings.  It took about 30 minutes to change them out with the motor on the bench.  As I recall there is a wave spring in each end bell, I can't find a good exploded view of that motor.


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## ErichKeane (Dec 20, 2019)

JimDawson said:


> I put new bearings in my 15 HP Baldor, I think it was about $25 for the two bearings.  It took about 30 minutes to change them out with the motor on the bench.  As I recall there is a wave spring in each end bell, I can't find a good exploded view of that motor.



I wasn't afraid of the bearing cost, more afraid of the motor replacement cost (if I ignore this and it was bad).  Taking the motor out of the lathe ends up being an event (I cannot get a hoist in there), and I'd likely need a hoist to move it anywhere in my shop.  The more I think about it, the more I think that replacing the bearings needs to be near the top of my TODO list though.


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## JimDawson (Dec 20, 2019)

New bearings cant hurt.  You might pull the belts off and turn it on and see of the noise goes away.  It could be the belts slapping around a bit or something in the lathe.  If you turn the motor by hand and the bearings sound OK, then they probably are.


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## ErichKeane (Dec 20, 2019)

JimDawson said:


> New bearings cant hurt.  You might pull the belts off and turn it on and see of the noise goes away.  It could be the belts slapping around a bit or something in the lathe.  If you turn the motor by hand and the bearings sound OK, then they probably are.



Its a chain, and the rattle happens without the chain installed.  I'm unsure if it is the motor though, there is enough metal things around that it could just be hitting the resonant frequency of SOMETHING else, but I don't know.  There is a thick layer of grease/dirt over the motor/surroundings, so it could be a lose washer or something and I'd have no idea.

The motor turns fine by hand, and I didn't notice anything bad sounding but perhaps I'll try again.  I might just suck it up and see what it'll take to get it out of there to replace the bearings for peace of mind.  That, and to harvest that 1/4" thick layer of dirt


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## Ulma Doctor (Dec 20, 2019)

I hope i'm not too late for the party here...

it is common for motors to have thin wavy washers at one end
the wavy washer gives a little when the motor is starting. 
after the spring pressure overcomes the initial longitudinal movement, the motor shaft returns to the path of least (mechanical)resistance

i would not usually expect to see 1/2" of end play movement, especially in a 3450rpm motor

i have experienced motors that have thrown the inner dust shields from the bearings and making one heck of a noise
you may(or may not) have a similar situation

simply mark both ends of the motor end caps relative to the field housing, so as to assure proper re-assembly
pop the pulley off the business end
remove the bolts running through the motor
knock the end caps off with gentle persuasion
the bearings will then be exposed
a 2 jaw or 3 jaw puller can then be used to remove the bearings
if you take a look at the namplate, (baldor often used to put the bearing numbers on the nameplate)
otherwise look for identification numbers,( ie.6207- 6307 were common bearings used for that hp range of motors)
otherwise extract the bearings and measure ID, OD and Thickness in millimeters and you can find the bearings through reverse osmosis

at this stage inspect the wavy washer, look for cracks or broken pieces

re-assemble in reverse order!


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## ErichKeane (Dec 20, 2019)

Ulma Doctor said:


> I hope i'm not too late for the party here...
> 
> it is common for motors to have thin wavy washers at one end
> the wavy washer gives a little when the motor is starting.
> ...


Not too late  it was late when I got home from work, so I didn't get a chance to try and pull it out. At 300 lbs, removal is likely to be an adventure !


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## C-Bag (Dec 20, 2019)

Years ago I bought a mechanic stethoscope and it's amazing what you can tell about bearings with it. Lots of times I could hear a rough bearing long before it got bad enough to feel play. It was the only way to hear all the different bearings in the accessories on a running engine not to mention lifter and tappet noise etc. it was also great for listening to bearings on electric motors and gear reduction boxes.


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## Downunder Bob (Dec 21, 2019)

The wavy washers are there to allow the armature to float axially so that when running it find its magnetic centre. if a motor is forced to run out of magnetic centre it will run hot and noisy. it allows the machining tolerances to be rather loose.


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## RobertB (Dec 21, 2019)

Downunder Bob said:


> The wavy washers are there to allow the armature to float axially so that when running it find its magnetic centre. if a motor is forced to run out of magnetic centre it will run hot and noisy. it allows the machining tolerances to be rather loose.


Yes, also to allow for thermal expansion of the shaft length. But this is usually in the 0.040" range, 1/2" is pretty extreme. That much I think warrants investigating. Some motors have snap rings either on the shaft or in a groove on the bearing itself for locating. One of those failing could result in excessive end play. Some use bakelite washers to shim for end play and they sometimes fail with age.


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## ErichKeane (Dec 23, 2019)

Alright... I had some time to take the motor out of the lathe, which was a giant PITA.  I ended up discovering that a panel came off the lathe REALLy late, so I ended up trying to wrestle it through a hole that was only slightly too small.  I FINALLY got it out though, and started tearing it apart:

First, I gave it a wipe down, and took this picture (and of the data plate):








I used a pulley puller to take off the toothed pulley, and took off the rear fan guard.  The pulley side ended up coming off pretty easy:






The rear fan I ended up breaking unfortunately (it was tac welded to a collar that was held in by a hidden-in-dirt set screw) using my pulley puller.  Hopefully I can just flatten it out and JB weld it back together (or would there be a source of replacements?).




THEN, the other endcap came off.  Bearings on each side are the greasy on 1 side, sealed on the other kind, and had some 'grit' to them.  The pulley side (the one with an accessdoor!) had been greased it seems, but the other had a much older grease in it:




I was able to pull the back bearing off pretty easily, so the whole shaft assembly came out. It seems REALLY clean inside:



I was able to pull both bearings out reasonably easily.  I ended up having to grind my pulley puller a little to get in to the pulley side, but it worked.







There was only a SINGLE wave washer on 1 side, I suspect the other should be in there too?  There was a decent amount of play (I think my 1/2" was way more than it really was... I was able to move it by hand ~1/16" of an inch).

Bearing #s seem to be (fan side): 6206 C3, and pulley side: 6307 (also seemingly C3).

First, where is the easiest place to get replacements that I could also get wave washers too?  Could I possibly replace these with fully sealed bearings so I don't have to worry about the grit?  Does anyone know if that rear fan is replacable, or if I should just try to JB weld it back together after bending it flat again?

Thanks!


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## RobertB (Dec 23, 2019)

The wavy washer is usually only on one end of the motor. Replacement fans are usually available for most Baldor motors. I would not try to repair the broken one, almost any repair would likely throw it out of balance.

A local bearing shop should have both, or any of the normal online suppliers like McMaster.


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## Ulma Doctor (Dec 23, 2019)

i concur with not trying to JB the fan.

if you have means to tack weld the fan back into position, you may be able to save it that way
but adhesives or epoxies wouldn't stand up to the job.

get a quality brand of bearing.

SKF
FAG
INA
Fafnir
NSK
NTN

are all quality bearings.
available on ebay, amazon, Motion Industries, Kaman Bearing, King Bearing, McMaster Carr, Zoro Tools, Grainger, etc.


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## ErichKeane (Dec 23, 2019)

I note that the broken fan is the external one... It doesn't seem like it actually does anything though, the motor itself seems sealed, but this fan just sits out the back..

I picked up a pair of ZZ c3 bearings for it, a replacement fan that looks like the right one, and a new wavy washer, so hopefully it'll go back together alright


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## Downunder Bob (Dec 24, 2019)

That external fan cools the motor by cooling the casing. the casing gets hot by conduction from the internals and by cooling the casing the internals can be kept at a safe temperature.


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## RobertB (Dec 24, 2019)

Downunder Bob is correct, that's why these motors are called TEFC, stands for "Totally Enclosed Fan Cooled"


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## ErichKeane (Dec 24, 2019)

Everything about this motor seems like overkill for me, so I'm not particularly concerned. I DID find what looks to be a replacement, so that will be here in a bit more than a week.

I did note that the motor wires aren't obviously marked, which is going to be a difficult time too... I ended up pulling them apart while dragging it out of the lathe, so at one point I need to figure out which is which!

At least the set of 3 that need to be connected to each other are still together, so I only have 6 to identify.


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## RobertB (Dec 24, 2019)

Carefully clean the wires and look for numbering on them. Don't us any solvents to clean them. Sometimes the wire numbers are printed on the wires, but unlike the wire data (gauge, temp rating etc.) that is often under a clear layer, the wire numbers are printed on the surface and can be wiped off very easily if the wrong cleaner is used..


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## middle.road (Dec 24, 2019)

Gotta see a picture of the lathe if you have time.


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## ErichKeane (Dec 24, 2019)

Here's an album I put together when i brought it home: 



https://imgur.com/a/QB44wrb


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## RobertB (Dec 24, 2019)

Yowser! That thing is spotless!


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## middle.road (Dec 24, 2019)

Yowser is right. She's a beaut! Just look at those tags. US Navy? Wonder if it started out life on a ship?
Is that a 6" (or so) horizontal mill in the background of your picts? (Left side) Or a CNC? Can't quite tell.


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## ErichKeane (Dec 24, 2019)

middle.road said:


> Yowser is right. She's a beaut! Just look at those tags. US Navy? Wonder if it started out life on a ship?
> Is that a 6" (or so) horizontal mill in the background of your picts? (Left side) Or a CNC? Can't quite tell.



Yep! 2 owners ago apparently bought it off some Navy ship when it was being decommissioned in San Diego, found its way via estate sale up to Oregon as part of a large lot, then sold to me cheap 

Only the top 3 pictures are in my shop, the ones on the bottom are the place i bought it.  My mill is in the background to the right (Green/white striped Powermatic/Burke Millrite).  Its manual +DRO +XPowerfeed. I don't really know what that horizontal mill looking thing in the background is, I know there is a giant surface grinder back there, but thats all from the shop I bought this from.


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## middle.road (Dec 24, 2019)

It would be neat to know what ship she was on, just for grins and conversation.


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## ErichKeane (Dec 24, 2019)

middle.road said:


> It would be neat to know what ship she was on, just for grins and conversation.


I agree! Sadly, I cannot seem to find any records from the Navy about which ships even got this model.


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## ErichKeane (Dec 31, 2019)

Update without pictures 

I got it fired back up and the rattle on startup is gone!  I ended up just going to VXB.com and getting Nachi bearings, and for $50 found an identical replacement fan.  I don't hear any other difference, but at least my lathe is back working!


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