Help me Make my GCFI Stop Tripping

That looks, at least from the rear to be a standard GE motor type. I've got a few 1/4 & 1/3HP floating around here.
Once you get a picture of the tag we can roll from there.
They're not real 'industrial' grade motors IIRC.
 
Chips O'Toole said:
I'll try to take a photo tomorrow if there isn't too much pus oozing out of me.
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Looks older judging by the oil cups...
I thought that maybe 1/4HP seemed smallish for a grinder, then I went digging around on gorton-machine.org and found that the 375 uses
a 1/4HP - 1725RPM motor. Shows ya what I know.
 
I have read that the only way to test a motor's windings correctly is to use an expensive megohmmeter I don't have. If that's wrong, feel free to let me know.

I'll post a photo of the motor. I don't have a shot of the nameplate right now. It's a 1/4-HP GE. I believe it says "Type M" on it. I haven't made any effort to find out what that means. In the photo, you can see the rubber mounts which I don't know how to remove.
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1. You don't need a megohmeter, you only need a regular one which you already have. Check from hot to ground, check from neutral to ground. (you already know from checking hot to neutral that the windings are ok at 2 ohm). You are looking for ground faults, not high voltage insulation failures. You should see infinity readings, anything else is a problem. Also check the wiring from plug to motor etc. is correct and not hot/neutral swapped or ground missing.
2. Unless you find something wrong with the motor, don't take it apart. And so removing those isolation mounts is of zero relevance to any issues that there might be, unless they are trash (which they don't appear to be). At worst once you get the spindle sorted out you can put a similar 1/4hp motor on it to test.

This will sound harsh, rude or impolite but you need to a) slow down, b) pick whose advice you are going to follow, c) get methodical on how you approach this refurb/re-awakening of this machine. There are a lot of opinions already in this thread. Some are on target, some are noise.

Start a check list of things to check so you don't forget them along the way. And take photos of every step as you disassemble (notice that I repeated that :) Ask me how I know. :)

And most importantly get a manual and parts breakdown before taking anything apart. Take lots of photos before you and during disassembly. As far as I can tell there is none available for free online as a .pdf other than a catalog. The link I provided is the only source I found.

While you are not well enough to focus on working, take a bunch of photos so we can see what all you got with the machine, and what the spindle looks like from both ends.
 
ub27Rocks said:
Yes, I understood what you believe. However you do have a meter so it seems best to just check for total isolation of hot and neutral from ground/frame? And that the cable from machine to wall is actually wired correctly.
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GL said:
I had random trips on a GFCI outlet in the basement. It had a refrigerator and a deep freeze plugged into it. The research I did at the time indicated that GFCI outlets like resistive loads but not inductive loads (like motors starting). Since these appliances were in the basement, and you don't look at them often, a trip can be a major expense. So, while not to code probably, the outlet was pretty high on the wall and I have a gravity drain to let any water out, I changed to a standard plug and got on with it.

I suspect the "belt off doesn't trip the outlet" is the difference in induced load when the rest of the machine has to spin up.
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Seems to be a lot of "foo-fah-rah" over the question of motor vs GFCI. Now there's a lot of "possibilities" here. A GFCI circuit looks at the difference of current between line and neutral. I don't use GFCIs on motor circuits. Against code authorities sure, but I prefer to do things right rather than "to code". Codes are just minimum acceptable. A political statement here, possibly deletable.

The OP mentions motor bearings. The motor bearings may be worn enough to allow the rotor to rub against an internal wire. Without the side pressure of the belt, this is a very plausable cause.

Belt off could well be static build up some where if the machine frame isn't properly grounded. Without a GFCI, you'd know as soon as you touched it when running. If you survived~~~

Remote troubleshooting is at best a troublesome project. There are any number of causes, most of which are plausable. The GFCI itself might be at fault. They degrade a little every time they trip. I could go on for hours on this subject. But I find myself forgetting where I was headed on a subject.

.
 
The bearings I'm concerned about are on the spindle, not the motor. Once I saw the oil cups, though, I wondered if they had ever been used.
 
The suggestion that I don't have a plan it's not really correct. my plan is to fix the bearings, and then if the motor stops tripping the GFCI, I plan to put the grinder back together and use it. If not, I plan to investigate other causes. Obviously, this is the logical way to go about things.

The grinder will not work with bad bearings. They have to be fixed. I'm fixing what I know has to be fixed before moving into other areas.

If it works well with new bearings, there is no reason to do anything else to it.
 
I missed that it is the spindle bearings thsat are bad, I (and I think a few others) thought you were referring to replacing the motor bearings before anything else. It is certainly a reasonable course of action to be working on needed machine repairs while working on the motor issues.

As mentioned above, a meger test is better but a standard ohm meter will still find most of the faults.
 
I think this thread may be annoying some people, and I'm afraid I'm here to make it worse. The motor has started working for no discernible reason. It starts with the belt attached, and I even started it while applying pressure to the pulley to make the motor work harder.

I have done nothing to the motor since the last time it popped the GFCI, except for adding oil to the cups. I don't see how this could matter.

The bearing on the wheel end is no good. I can confirm that. It gets too hot to hold onto after a few minutes. The other bearing stays cool. I don't know how bad things are. I have not measured the RPM's yet to see if the bearings are slowing the motor down.

I had never seen this type of motor before, so I thought it was pretty fancy. I have since learned that 1/4-HP 1725-RPM motors with rubber mounts are very common. TEFC jobs cost around twice as much, however, so I'm glad I don't have to buy one right now.

I have been trying to open the spindle with a pin wrench, but it's not going well. The slots are getting chewed up. I drilled two new holes for the pins. I could get a better grip on the nut if the inner spanner nut were out, so I'm going to see if I can remove it. I am hoping there is no shoulder trapping it under the big nut. I'm off to the auto parts store to buy two 1/2-20 nuts so I can grind them down and turn them into jam nuts for immobilizing the spindle.
 
Hi, can you post again a photo of where you are wrenching on? And don't forget, it might be LH thread. I assume you got the hub off (the thing with 1 1/4" diameter hub that looks as if it has a ground surface where the grinding wheel butts against?
 
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