# Lathe Motor Problem - I Think.



## HBilly1022 (Dec 19, 2017)

Working with the 12 x 36 lathe today and I shut it off to check a dimension and when I go to start it again, it won't start. Makes a clacking sound and then just hums. Did this several times then I started looking for the problem. Took the side cover off the headstock and could see the motor try to turn when it was powered up but it wouldn't go. I checked to see if something was jammed but everything turned freely, even the motor pulley. The motor wasn't hot either. Tried spinning the motor to a different start location and still nothing. Then suddenly it starts and runs fine for about an hour. Then the same issue again. One time it started but the chuck rotated very slowly and took about 3 seconds to get up to speed. Then I start hearing intermittent noises while the lathe is running. First I thought it was a belt that broke or was rubbing on something. Checked that and no issue there. Then I thought it might be in the headstock and pulled the cover to see and feel if there was anything going on in there. Couldn't find anything. The last time I thought it might be coming from the motor but it's hard to tell. I go in for dinner and when I go back the shop the lathe starts up like it should and ran fine for the rest of the night, maybe 45 minutes.

I started thinking it might be a bad motor or maybe a loose connection somewhere but the noise confuses me. I'll see how it goes tomorrow and maybe start checking connections.


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## Ulma Doctor (Dec 20, 2017)

i'd be suspect of a bad starting capacitor, or malfunctioning centrifugal start switch.
it wouldn't hurt to check connections at the motor and at the start/stop switch


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## Groundhog (Dec 20, 2017)

Don't start this stuff about 12x36 lathes. Mine made a couple of loud bangs and pops the last couple of times I've used it. Thought a hammer might of vibrated off and hit the floor - but no hammer. Sounded like an electrical snap. Can't find anything obvious.
And since I'm not a motor guy I can't be of any help to either of us so . . . since both lathes seem to be running at the moment lets just pretend we didn't hear anything or have any problems. Maybe the lathe gremlins will go somewhere else? Ya think?


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## markba633csi (Dec 20, 2017)

Ulma is on to it- probably need new motor capacitors; how many hours on your lathes guys?
Mark S.


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## woodchucker (Dec 20, 2017)

HBilly1022 said:


> Working with the 12 x 36 lathe today and I shut it off to check a dimension and when I go to start it again, it won't start. Makes a clacking sound and then just hums. Did this several times then I started looking for the problem. Took the side cover off the headstock and could see the motor try to turn when it was powered up but it wouldn't go. I checked to see if something was jammed but everything turned freely, even the motor pulley. The motor wasn't hot either. Tried spinning the motor to a different start location and still nothing. Then suddenly it starts and runs fine for about an hour. Then the same issue again. One time it started but the chuck rotated very slowly and took about 3 seconds to get up to speed. Then I start hearing intermittent noises while the lathe is running. First I thought it was a belt that broke or was rubbing on something. Checked that and no issue there. Then I thought it might be in the headstock and pulled the cover to see and feel if there was anything going on in there. Couldn't find anything. The last time I thought it might be coming from the motor but it's hard to tell. I go in for dinner and when I go back the shop the lathe starts up like it should and ran fine for the rest of the night, maybe 45 minutes.
> 
> I started thinking it might be a bad motor or maybe a loose connection somewhere but the noise confuses me. I'll see how it goes tomorrow and maybe start checking connections.


Is this a single phase, or 3 phase motor?
Does it have a capacitor if single phase? (most likely bad) or the switch to engage/disengage the cap is stuck.


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## HBilly1022 (Dec 20, 2017)

Groundhog said:


> Don't start this stuff about 12x36 lathes. Mine made a couple of loud bangs and pops the last couple of times I've used it. Thought a hammer might of vibrated off and hit the floor - but no hammer. Sounded like an electrical snap. Can't find anything obvious.
> And since I'm not a motor guy I can't be of any help to either of us so . . . since both lathes seem to be running at the moment lets just pretend we didn't hear anything or have any problems. Maybe the lathe gremlins will go somewhere else? Ya think?



With my luck the gremlins would just to my mill, which is only a few feet away. 

This is a single phase motor 1.5hp (9 amps) 60 hz. Looks like it has 2 capacitors, 2 circular humps on the motor. The lathe has maybe 30 or 40 hours on it, tops. It's only 3 months old. I'm going to check connections this morning and run it again to see if it happens again. It was really weird yesterday because it did it once for quite a while then ran fine for maybe 30 minutes then it did it a bunch of times in succession. Then after it cooled down for a while, it worked fine.

I had a motor problem with the new mill drill I bought last year and the distributor ended up sending me a new motor. It had the same issues and he sent me another motor. All has been good since then, although the motor runs very hot. Can't keep my hand on it for more than a few seconds.


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## Groundhog (Dec 20, 2017)

HBilly1022 said:


> With my luck the gremlins would just to my mill, which is only a few feet away.


 
Bearings in my CNC mill shot craps 2 weeks ago. Bottom bearing is not available anymore (in a quality grade). Thankfully found a NOS complete spindle. It should be here shortly after Christmas.

Now my air compressor has started knocking. It has a ton of hours and I'm guessing either a rod bearing or a cracked piston. Headed out to the shop to tear it apart now.

At least I'm not running out of things to do while I'm trying to practice being retired!

Sorry I'm not being any help with your problem. I'll shut up and let the knowledgeable inmates help you!


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## markba633csi (Dec 20, 2017)

Capacitors can sometimes fail quite early "infant mortalities" and others can go seemingly forever. The one on my '78 taiwan bandsaw is all discolored and bulging yet it spins the motor right up just like it's brand new. Go figure. If you have a multimeter you can do a simple test on your caps; disconnect cap, discharge it, then test for resistance: you should get an initial low ohms reading which then climbs toward infinite ohms. Reverse the test leads and you should see the same thing. Each time you reverse the leads you should see the same thing: Low ohms climbing toward high.  If you see an open circuit or a constant low ohms reading the cap is bad. This test won't measure the actual microfarad value, it's just a go/no go check. Some digital meters can.
Mark S.
ps this test is easier with an old style "needle" analog meter, anything from a Radio Shack cheapie, to a fancy Simpson or Triplett meter.
pss discharge the cap first by shorting across the terminals with a screwdriver before testing


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## Mitch Alsup (Dec 20, 2017)

woodchucker said:


> Is this a single phase, or 3 phase motor?



Technically, induction motors are 3 phase. In single phase use, the master phase and the inverse phase drive 2 of the three coils, and the run capacitor generates the third phase. In this kind of use only 80% of the TQ and HP that the motor could produce with real 3 phase power is produced. The starting capacitor is used to accentuate the phase difference on the 3rd coil so the motor has good TQ at lower RPMs and a switch cuts it out as the motor comes up to speed.

ETA:: 3 phase motors don't use the capacitor(s) and can also be switched from run forward to run backwards instantaneously, whereas 1 phase used as above need to almost stop before reversing.


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## woodchucker (Dec 20, 2017)

HBilly1022 said:


> With my luck the gremlins would just to my mill, which is only a few feet away.
> 
> This is a single phase motor 1.5hp (9 amps) 60 hz. Looks like it has 2 capacitors, 2 circular humps on the motor. The lathe has maybe 30 or 40 hours on it, tops. It's only 3 months old. I'm going to check connections this morning and run it again to see if it happens again. It was really weird yesterday because it did it once for quite a while then ran fine for maybe 30 minutes then it did it a bunch of times in succession. Then after it cooled down for a while, it worked fine.
> 
> I had a motor problem with the new mill drill I bought last year and the distributor ended up sending me a new motor. It had the same issues and he sent me another motor. All has been good since then, although the motor runs very hot. Can't keep my hand on it for more than a few seconds.


Sounds like the capacitor is not working. But it also could be the switch. When the motor spins up, do you here the switch kicking out after a  second or 2?  If you don't here that click take the endbell off the motor and see if it is stuck. Make sure you unplug b4 hand, if that is fine and moves in and out smoothly, then take the cans off the capacitor. See if either has blown, (don't touch). Follow Mark's test recommendations.


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## HBilly1022 (Dec 20, 2017)

I sent an email to the head office of King Canada yesterday and got a call from my selling dealer this morning, telling me that King called them this morning and told them they are sending me a new motor. King asked them to check with me to see if I would install it. If not the dealer will have to make arrangements to get it done.

Think I will do it myself. Not hard and probably way faster than trying to get someone out to our place, in the boonies.


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## Groundhog (Dec 20, 2017)

Great!


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## Ulma Doctor (Dec 20, 2017)

nice, i hope it all works out!


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