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Repair lathe motor?

Discussion in 'OTHER BRANDS OF MACHINERY' started by ScrapMetal, Mar 29, 2012.

  1. ScrapMetal

    ScrapMetal Active User Active Member

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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".

    [​IMG]

    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
     
  2. Tony Wells

    Tony Wells Administrator Staff Member Administrator Active Member Director

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    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.
     
  3. 8ntsane

    8ntsane Active User Active Member

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    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.
     
  4. Tony Wells

    Tony Wells Administrator Staff Member Administrator Active Member Director

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    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.
     
  5. R.G.

    R.G. Active User Active Member

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    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.
     
  6. ScrapMetal

    ScrapMetal Active User Active Member

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    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
     
  7. R.G.

    R.G. Active User Active Member

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    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.
     
  8. Hawkeye

    Hawkeye Active User Supporter Active Member

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    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.
     
  9. ScrapMetal

    ScrapMetal Active User Active Member

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    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
     
  10. R.G.

    R.G. Active User Active Member

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    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.

    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.
     
  11. Kevinb71

    Kevinb71 Active User Supporter Active Member

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    Having worked in a motor shop 25 yrs ago while I was going to school I will tell you what I learned.
    Before doing anything else check how much "up and down" and "in and out" play there is on the shaft. Then pull off the capicitor as mentioned by R.G. A motor shop or some electricians can test this with a meter. If that all is ok then do the following.
    1. Next write down how the wires are hooked up now. By color code or on a motor of that age by number on the wires! GE was always a little different than everybody else.
    2. Before you pull the four long bolts holding the end bells to the middle(stator) section scrib a line fom the end bell on to the main body. One line on the shaft end bel and main body and two lines on the opposite end(start switch end. These are for reference later to get the end bells back on in the same position. Some of these older motors weren't always machined perfectly and if you get them "out of line" you can mess up the clearance of the rotor to the stator and it's hard to sort out.
    3. Take and tap the end bell shaft end loose from the main body and slide the rotor and end bell out of the stator. That way you don't have to fight with/break the start switch and wiring. It's all at the "non shaft" end. There will be a centrifigal switch operator on the end of the rotor. It probably has two springs and a flat plate/washer that you should be able to push in on and it will pop back out on it's own. This operates the start switch.
    4. Take a look inside at the motor windings. It's usually fairly obvious if the windings are burned out. Some will be bright or maybe a dark copper color and some will be "BLACK". If the are portions that are black you would probably need a different motor. They can be rewound(i did it ) but it is harder than I can explain here plus you have to find the right size wire.
    5. Tap the other end bell loose carefully and watch how the wires are routed to the switch and windings. carefully lay the end bell down interior side up. The start switch will be mounted to the end bell. There are usually one or two contacts on the switch. Do they appear good and clean or dark and burned? Think points on a car(if you are old enough to know what they are:biggrin:.
    iF ALL THIS APPEARS GOOD. How much play in and out play was there? Sometimes they wear out fiber washers(on the shaft between the shaft and end bell) and to much play won't let the start switch work properly.

    The old motors like this one really are the best ones ever built (LOOK AT HOW OLD IT IS NOW) and if you can get it back up and purring that's how I'd go.

    Post a picture or two of the inside if you question how something looks.
     
  12. ScrapMetal

    ScrapMetal Active User Active Member

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    R.G. - Yep, I'm familiar with ohmmeters, I don't have a Simpson 260 sitting around but I can pull out my Fluke 87 and get pretty much the same thing done. :p:lmao: (Sorry, had to mess with you a bit even though you have no way of knowing that I majored in electronics engineering some 25 -30 years ago. :biggrin:) Good advice given. I'm not familiar with the layout of this old of motor though. I will be trying to get some good pics tomorrow. I may even be able to get some pics on the interior (wife got me an electronic bore-scope for Christmas that I haven't had a chance to use yet). Oh and no real "bulge" on the motor itself, pictures again. ;)

    Kevin - Where to start? Okay, write down the wire hookups? All black. :banghead: Wait 'til you see the pics, you'll love it. :p The motor shaft itself it rock solid, no extraneous movement up, down, in or out. I really like the attitude, "The old motors like this one really are the best ones ever built". :thumbzup: I'd like to save it too.

    Pics to come shortly,

    -Ron
     
  13. R.G.

    R.G. Active User Active Member

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    Another EE? Ok. And may God have mercy on your soul. :D I do have a Simpson 260, but it was given to me as a legacy.

    Mmmmm. That probably means they got self-starting with a resistance-split phase. The lower-end induction motors bypass the motor start and run caps with a high resistance winding. At startup, the main power winding is low resistance and appears highly inductive, and the high-resistance winding keeps a nearly resistive impedance. This makes for a partial second phase, enough out to let the rotating magnetic field get the rotor moving, and after that, induction takes over and the reaction of the rotor field keeps it running like it would if it had a start cap that dropped out.

    That gets you lower starting torque than a capacitor start or run motor. Still, it's been working for you. That opens your range of replacements a bit. If it were me, I'd look for a cap-start or cap-run motor to replace it. These versions have better starting torque.

    I bring this up because the lack of a capacitor phase split means that it's not as simple as clipping in another cap. If it's a resistive-split phase, that puts it into the rewind or replace category, because there's only the windings doing the work. I'm not a motors expert, but I played one back in the power supply design lab. :D


    Kevin's advice is really, really good. Pictures, lots of pictures, and disassemble so you can find and fix.

    However, at this point, my 'it's gotta work by tonight' demon prods me and says that you oughta buy a physical replacement motor used and cheap, install it in the lathe, and then work on refitting the old iron.
     
  14. R.G.

    R.G. Active User Active Member

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    You know, I wonder if the motor is jumperable 110/220 and the jumpers have corroded.

    And I wonder if the continuous increase in wall-socket voltage is just flat overvolting it. Wall sockets used to provide 110Vac, as the name plate says. Over time this has increased until I get 125Vac out on the end of a long, skinny, rural distribution wire. This is a common problem in vintage guitar amps (I deal with these in my day job) and can wear them out pronto. In a motor, it would lead to heating, and the cumulative effect could be to burn wire insulation.

    Just speculation.
     
  15. R.G.

    R.G. Active User Active Member

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  16. R.G.

    R.G. Active User Active Member

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    Real amps glow in the dark.

    'Course, when welders do it, sparks fly. :biggrin:
     
  17. Tony Wells

    Tony Wells Administrator Staff Member Administrator Active Member Director

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    NO PICKING ON THE 260's!!! I have a fleet, and a couple of 160's as well. I use a 260 regularly.
     
  18. ScrapMetal

    ScrapMetal Active User Active Member

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    Make that another :+1:

    [​IMG]

    Also have a Matamp Minimat and the wife bought me a Mesa Transatlantic TA-30 Combo for Christmas. :biggrin:

    :lmao: No problem Tony. Most of my experience with them was back in school and their survival rate was horrendous with many of the students (true "dip sticks" ) switching ranges without disconnecting and frying them left and right.

    Okay guys, I promised some pics today. Here goes.

    [​IMG]

    [​IMG]

    Under the little "oval" plate is access to the brushes. I couldn't get a clear picture of them so I didn't bother to post the resulting blur.

    [​IMG]

    [​IMG]

    And finally, my favorite...

    [​IMG]

    Nice installation huh? :rolleyes: :lmao: I haven't dared to take off the old cloth electrical tape as it's a little "crunchy" and I'd rather keep the lathe "runable" 'til I'm prepared to actually do something about it.

    -Ron
     
  19. R.G.

    R.G. Active User Active Member

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    You're doomed. At least you haven't developed a taste for JMI Vox amps. Might as well like absinthe.

    Comments on pictures:
    (rating plate)
    OK, 1/2Hp, 110V 60 cycle 1780rpm (that's good), foot mounted. If you'll measure the shaft diameter and footprint hole pattern, you can pretty much directly pick a replacement. I think...

    ... brushes... ?? There are brushes in there?? Are you sure?? One of the reasons to use a split phase induction motor is that it doesn't need brushes at all, so there's nothing to wear out.

    Is there a commutator or slip rings in there?

    Are you sure it has brushes?? Brushes make it into a different animal. If there is a commutator in there, it's a big "universal" type. If there are slip rings, it's a wound-rotor type. I've read about wound-rotor induction types, but I don't think I've ever actually seen one.

    Is that maybe access to a centrifugal switch to switch out the start winding?

    Brushes... AAACCKK!!! Brushes...

    That last run of comments flips my advice over to "find a used replacement motor and put it in. Then do your rebuilding at a leisurely pace."

    Look here: http://austin.craigslist.org/tls/2877966495.html
    I think numbers 3 and 4 might drop in if they are foot mounted. Can't tell from the pictures.
     
  20. Hawkeye

    Hawkeye Active User Supporter Active Member

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    Hah! I ran the model number through Google. I got 10 hits, all originating from HM. :lmao: There's not much info on that motor on the net.

    Is it possible that what you are seeing under the oval plate is the start switch mechanism? You don't usually see a universal motor in that size. (At least, not any more.) If it was for brushes, I'd expect to see another plate on the underside.

    If the start switch is not opening, it will keep the start winding in play all the time. This will definitely cause quick heating. Try removing the oval plate and watch the switch mechanism while it is starting up. If it is opening, you will usually see a spark and hear a click when the start winding drops out. If not, check for grunge on and around the mechanism, broken springs, or pieces obviously out of place.

    According to the plate, it is 110 Volt only. The fact that there are four leads coming out to the JB shows that it is likely reversible.

    If you do take the connections apart, pick up some screw terminals large enough to take all the necessary wires. They come is strips of 12 and can be cut to length.
    P4210014a.jpg
     

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