Repair lathe motor?

ScrapMetal

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I have (as best I can read off the tag) a GE, Model# 5SCA65AA6, Type SCA, 1/2 HP, single phase, 110v motor powering my SB 11".



The motor gets very hot and it does it rather quickly. It will start to make "strained" noises short time which can be alleviated by oiling the bearings but it only lasts for a short time. Applying the oil to the bearings is like dumping it on the ground as the oil just runs through it. Yes, I can switch to a higher viscosity oil but I'm pretty sure the bearings need some work.

How much effort is it to rebuild one on these? Am I looking at bearings or bushings? Is it "worth it" to try and rebuild this motor or just go with a newer and probably more efficient option?

I'd like to hear some opinions.

Thanks,

-Ron
 
Likely sleeve bearings, which are babbit plated steel. You could make some new ones of bronze, but you would need another lathe. Unlikely, but not impossible that a motor shop would sell you some. They press in, which of course means knock the old ones out with a drift, and press in the new ones, aligning the oil hole.
 
Ron
I would look around, and get a general idea of price for a motor in your area. If new is out of the price range for you , a used motor might be worth looking in to.
I maybe wrong, but the bearings would normally be greased,No? I would also guess the bearing , or bushings should be fairly inexpensive, and shouldnt break the bank.

The only bummer about this, is once you pull the motor and tear it down, your lathe is down too. And you know the deal, thats just when you might need it.
Regardless, it might be worth taking it apart, just so you know what it needs, and how bad it looks inside. This might save you the BS of ordering bearings / bushings and wishing you just looked for another motor to start with.

Might check the local craigslist for a good used replacement first.
 
If you have a mill, you don't need a lathe to make new bushings, if it is a bushing as I suspect because of the oilers. You'll have to tear it down to see. I'm another who prefers repairing old motors if possible.
 
If it were mine, I'd pull that belt off the motor pulley and turn it by hand - er, power off, of course. If it's the bearings, you can feel it, and see how long it spins after being given a turn by hand. If it spins easily and smoothly, it's not the bearings. If it's hard to turn, yep, bearings or some built-up drag mechanism inside.

It could well be the motor start/run cap going bad. If that has not been replaced in your memory, it wouldn't be all that bad an idea to just replace it if the rest of the motor checks out. Motor caps are $5 to $20 items at HVAC supply places. This could cause the heat all by itself in some cases. A *shorted* or going-low-resistance motor cap causes a big electrical drag on the motor's rotation, as well as pulling a lot of current.

The other option is to trouble shoot by telephone. I'd spend an hour calling motor rewinding shops within a reasonable driving distance. I've had alternators rewound in the past; this cost in the range of $30-50. I don't know about induction motors.

Electrical motors are highly standardized. If you can get the motor speed off the rating plate as well as the other numbers, any 1/2HP 120Vac --same speed-- rated motor with similar mounting will work, and may be cheaper as a surplus item.

A quick look at ebay shows:
http://www.ebay.com/itm/ELECTRIC-MO...601?pt=LH_DefaultDomain_0&hash=item3a698c7029 : 1/2HP 120vac 1ph 1800rpm, $110 including shipping, new, 5yr guarantee
http://www.ebay.com/itm/1-2-HP-ELEC...789?pt=LH_DefaultDomain_0&hash=item3a6b4ce97d : 1/2HP 120VAC 125rpm, $100 including shipping, reversable

searching on "electric motor 1/2HP" turns up 13 pages of motors. You have to match the voltage, phases, power and speed, as well as the mounting, which is a foot type on yours.

And, just because the devil is sitting on my shoulder tonight, if you were to buy a DC motor, you'd get infinitely variable speed. You'd have to get one rated for the same or higher HP (note, treadmill motors are notoriously overrated) and about the same speed, you'd only have to adapt it and a DC motor controller to get really wide speed variation.
 
Thanks guys. I personally like the idea of rebuilding but, as mentioned a few times, once I pull the motor my lathe is kaput. If I had a mill that would simplify things but the closest things I have at the moment are a crappy drill press and a huge doorstop that looks kind of like a shaper.

I don't know any of the history of this motor as it was bought with the lathe, from the widow of the previous owner.

Tony voiced what I was already thinking, "if it is a bushing as I suspect because of the oilers". The only way to know for sure will be to pull it apart.

Looks like that is going to have to be the place to start though it's going to kill be to "disable" my lathe.

Now, if I were to replace it, that opens up a whole new "can o' worms" as I have both 115v and 230v readily available and, darn you R.G. :biggrin:, the possibility of going to a D.C. system.

I'll let you guys know what I find.

-Ron
 
Do try spinning the motor by hand with the belt off. It will tell you semi-instantly if the bearings are binding.

I threw in that comment about capacitors because they often fail. It might be worth your time to take off the capacitor cover and pull out the cap for testing/replacement if you can get to it. Motor start and run caps (those are different) are cheap and easy.

One thing I forgot last night was craiglist. There's a guy on my local craigslist (which probably doesn't help you much) who is selling his accumulation of motors for $25 - $40 each. You might check your local craigslist for motors.
 
I think the ultimate solution would be to find a used motor and install it, then use the lathe as required to rebuild the old one. Even a yard-sale motor would keep you running. Just make sure it's got all the connections brought out to the junction box so it can be reversed.
 
That's a good point Mike. If a guy could pick up a used motor cheap enough it would make perfect sense.

I did pull the belt off today and spun the motor shaft by hand. Doesn't seem gritty at all and the shaft is rock solid with no "slop" what so ever. The "electronics" seemed questionable at best. I'll take my camera in tomorrow so I can take a couple of pics as it's kind of hard to describe.

-Ron
 
I did pull the belt off today and spun the motor shaft by hand. Doesn't seem gritty at all and the shaft is rock solid with no "slop" what so ever.
If it spins freely, and has no grit, resistance, or slop, you just saved yourself a fair amount of trouble. Bearings only need rebuilding if they're bad, and if they're not bad, rebuilding doesn't help at all.

The "electronics" seemed questionable at best. I'll take my camera in tomorrow so I can take a couple of pics as it's kind of hard to describe.
That would be a help. Bad connections/wires can be a problem; so can the start and/or run caps.

It is possible that there is a bum contact that only opens or shorts when it warms up. I've run into that.

Are you familiar with an ohmmeter? This is one of the settings on most electric multimeters. This can tell you if there is any electrical connection between the two probes. It's used for measuring resistance (ohms) and also for detecting the difference between open circuits and short circuits (that is, very low resistances). The motor should have two or more wires going in, and a third wire attached to the motor frame or one end bell. Neither of the power wires should be connected (shorted) to the frame, either end bell, the shaft, or the third wire safety ground. If either one shows resistance under maybe 1 megohm, the motor windings are compromised. If they're both over 1M, it's something else.

See if you can find out the value of the start and/or run capacitor, which should be in the "bulge" outside the motor frame.
 
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