Jet Midi Lathe keeps tripping reset

[William C Rogers]

I have a Jet 1014VS midi lathe that keeps tripping the reset. It resets, but at a small load it trips again. About 5 years ago I did replace the toggle switch, but have not needed to do anything since. Is this fixable by me? I had only been using it for buffing, but wanted to try and make a final instead of using my PM 90.

Good news is I have a Delta midi that I haven't used in a couple of years as a backup. I guess I will get it out of storage if this is a costly problem. I could set the jet up for only buffing ( until it finally dies ) if it will need a new motor.

[Don Jarvie]

May need to open it up and clean it up. Maybe dust has built up and the switch can't set.

[William C Rogers]

It's is resetting fine, restarts and then trips under light load. I am going to look at the motor brush and look/clean the breaker and switch tomorrow. I'm thinking it may be the circuit breaker that is weak. Nothing gets hot or anything like that, it just keeps tripping under a light load. Both parts are still available.

[Brice Rogers]

You mention that it trips the reset and also mention that it trips the circuit breaker. I presume that you are probably talking about the reset that is on the motor.

If it is the reset on the motor, it has two likely culprits: (1) the motor over-current breaker or (2) the motor is drawing too much current. How can you figure out which? Well, fortunately you mentioned that after you reset the device that it'll run until it goes under an increasing load. So, you can get an AC ammeter. I have one from Harbor Fright :eek: that can either be used as a clamp one (around a single conductor) or can be used with the included 120 V receptacle. Just get the lathe running and apply a load while watching the ammeter. I think that your Jet has a 1/2 HP motor, so if it trips at under about 4 amps, then your over-current device is weak and needs to be replaced. If the current is a fair amount over 4 amps and you aren't applying a horribly heavy load, then it is likely that your motor has a problem.

If you were talking about your breaker-box breaker, then the same measurement could be made. Breakers can go bad over time.

If you are talking about a GFCI breaker, pls. comment and I'll scratch my head a bit and respond.

[Mark Greenbaum]

This may be relevant: I had a 10" Craftsman Radial Arm Saw, and every time I'd put it under a load (trying to make picture frame mouldings in oak), it would trip the thermal overload on the motor. I ended up giving it to my Brother-in-law, and he just used a heavier duty extension cord, and it ran fine from then on. My wimpy extension cord was not rated to carry the load the motor was seeing. Try a heavier extension cord first, if it's the motor thermal relay that's been tripped.

[William C Rogers]

You mention that it trips the reset and also mention that it trips the circuit breaker. I presume that you are probably talking about the reset that is on the motor.

If it is the reset on the motor, it has two likely culprits: (1) the motor over-current breaker or (2) the motor is drawing too much current. How can you figure out which? Well, fortunately you mentioned that after you reset the device that it'll run until it goes under an increasing load. So, you can get an AC ammeter. I have one from Harbor Fright :eek: that can either be used as a clamp one (around a single conductor) or can be used with the included 120 V receptacle. Just get the lathe running and apply a load while watching the ammeter. I think that your Jet has a 1/2 HP motor, so if it trips at under about 4 amps, then your over-current device is weak and needs to be replaced. If the current is a fair amount over 4 amps and you aren't applying a horribly heavy load, then it is likely that your motor has a problem.

If you were talking about your breaker-box breaker, then the same measurement could be made. Breakers can go bad over time.

If you are talking about a GFCI breaker, pls. comment and I'll scratch my head a bit and respond.


Brice, thanks for the response, it is the reset on the motor. I have that amp meter, but seems to tough to separate a wire to test the load. I'm looking for a 8 amp fuse I can wire in to see if it will blow that. If that seem to work I will order the replacement motor reset breaker. I got the Delta setup yesterday after 3+ years in storage.

[William C Rogers]

I ran a wire from the reset breaker and measured the amps. With a light load it went to around 7 amps and with moderate load it peaked at times up to 12 amps. So I guess the breaker OK and the motor windings are going. I have the Delta setup and working fine. The Delta motor always did seem stronger anyway. Just miss the VS. I'll use the Jet for buffing until it dies. New motor is around $300, about the same as a used lathe this model.

[david privett]

I do not know what type of amp meter you have but if it is a inductive type get a male and female 120 volt plug put a foot of wire in between all 3 conductors ,plug the lathe in the female and the male in the wall, pull out the hot and place the inductive probe around it and turn it on and see what you get. You know there is a chance that it is a weak reset button also they are thermal switches and they can go bad.

[Bill Boehme]

Brice, thanks for the response, it is the reset on the motor. I have that amp meter, but seems to tough to separate a wire to test the load. I'm looking for a 8 amp fuse I can wire in to see if it will blow that. If that seem to work I will order the replacement motor reset breaker. I got the Delta setup yesterday after 3+ years in storage.

Brice's suggestion was spot on and that's how I also would have attacked the problem. I think that bypassing the reset breaker with a fuse is premature until you do further checking. The lathe uses a DC motor so the next step is to look at the brushes and commutator to see if they are worn out or damaged. Drawing 7 Amps under no-load conditions is excessive. I would next look for something that might be causing an abnormal load. I assume that have already done some fault isolation by removing the V-belt to rule out anything external to the motor, but in the off chance you haven't then that would be the first thing to check. Now, with the motor removed from external loads, measure the current. The next is to see if the motor shaft spins freely (with the belt still removed) -- before doing this remove the brushes to eliminate that source of drag then spin the shaft by hand. This will tell you if the bushings (or bearings) are bad. While the belt is still removed, check the spindle to see if it spins freely. If everything is OK so far, open up the motor housing and remove the armature. A common failure mode is for the windings to open up -- look near the commutator segments to see if there are any open wires ... often you will see wires sticking up because they will open up where they connect to a commutator block. This type of failure is normally the result of overloading the motor for an extended period. There is an avalanche effect because this places a heavier load on the existing windings ... so they overheat and ... on and on. If that is the problem then it's time to get a new motor. If everything is still OK, a reset breaker might be the problem. If you get a fuse then make certain to get a SLO-BLO type. Unlike in the good old days, small motors are now throw-away items and you might not be able to get any parts besides the brushes. So, armature, reset breaker, etc might not be replacement items.

[William C Rogers]

Thanks for all the help. I took the motor apart, blew it out (didn't see much of anything), looked inside over and did not see any anomalies. Cleaned commutator and brushes. Put it all back together and it was better but still not right. I estimate I have about 70% of new power, and it will still trip the breaker. So it is still drawing too many amps. I am just going to use it for buffing until it finally dies.
330530

One be of the things I liked was the metal handles for the tool rest and quill. They weren't interchangeable with the Delta, however the Jet tail stock and Delta head lined up perfectly point to point. I was supprised it did. So I am putting them on the Delta. Too bad I can't move the VS.

330531

The Jet is a 2004 and the Delta is a 2002. Now I can get back to turning.