Need help with large Jet grinder

[Jason280]

Salvage yard has had this large Jet grinder for a while, finally talked them into selling it to me. I knew wiring was probably an issue, but figured it was worth taking a chance on for $20.

Its a Jet BG-10, and the pic really doesn't do it any justice...its a beast. The switch is gone, and is pretty much straight wired. I got it home, and all it does is hum a little and rotate very slowly. You can spin the wheels by hand, but it still doesn't want to get up to speed. I'm not sure if its a capacitor or wiring issue, as the wiring is a mess underneath. The wheels spin easily, so I don't think its bearing related.

Did I waste $20, or is it likely something easy to fix?

 

[454ragtop]

If it spins slowly, i'm more inclined to think it's wired for 230, and you're running it on 115 volts. Might be the cap, but I'd check the wiring first. Also, I've said it before, and I'll say it again, quality grinders have cast wheel guards, not stamped tin.

 

[slip knot]

I agree it looks to be dual voltage. make sure your running it on the correct voltage

 

[Jason280]

I need to check the wiring, its likely all jacked up. I need to pull it all apart and start over, just to see what all is there. It has a 120v plug on it now, which is what I have tried it on...

 

[Jason280]

Here are some better pics...





...the capacitor






...NASA level wiring









These are the main wires coming from the motor. Two wires, black(?) and white, go to the capacitor, and there are two red and two yellow (marked 1-2-3-4).

 

[American Locomotive]

The two yellow and red wire would get connected in specific ways to enable 120 or 240v operation. Generally you'll be putting two sets of windings in parallel for 120v, or in series for 240v. It's pretty straight forward to figure out if you have a volt/ohmeter.

 

[doogdoog]

It says motor starting cap so it probably has a centrifugal switch that shuts off the starting winding by turning the cap off after reaching a certain rpm. The cap could be bad or the switch is not operating correctly like maybe dirty contacts.

 

[WittHay]

We had a 3/4" grinder different brand but same color and look as the Op's 1"

That thing took forever to get up to speed. and it would blow a 15 amp breaker. I installed a 20 amp breaker and was just patient on start up. Once running it was a powerful grinder.

 

[Provincial]

We had a 3/4" grinder different brand but same color and look as the Op's 1"

That thing took forever to get up to speed. and it would blow a 15 amp breaker. I installed a 20 amp breaker and was just patient on start up. Once running it was a powerful grinder.

This is a good description of every Jet bench grinder that I have encountered. Also the Wilton branded versions.

 

[Monkey Milk]

Bigger isn't always better, wait till you price out wheels for the beast

 

[Stereocraig]

I will have to agree w/ doogdoog on his observation of it possibly being the centrifugal switch stuck in the "run" position.
The motor will hum loudly,spin very slow and you could burn out the "run" windings.

Additionally, I have temporarily tested 230 motors on 115 before investing in a 230 plug. They seem to run at proper speed, but bog when put under load.

Your contacts may have arced together, or maybe the centrifugal weights are sticking from dirt and hardened grease.

 

[marinusdees]

I will have to agree w/ doogdoog on his observation of it possibly being the centrifugal switch stuck in the "run" position.
The motor will hum loudly,spin very slow and you could burn out the "run" windings.

Additionally, I have temporarily tested 230 motors on 115 before investing in a 230 plug. They seem to run at proper speed, but bog when put under load.

Your contacts may have arced together, or maybe the centrifugal weights are sticking from dirt and hardened grease.

240 volt motors run at proper speed on 120 volts because motor speed is a function of the frequency, i.e., 60 cycles per second. Motor power is a function of amperes consumed, and the motor consumes fewer amperes when incorrectly wired because the run windings are connected in series and not in parallel, increasing resistance and therefore reducing amperes consumed. This is an inexact explanation of this phenomenon, but serves.
If the centrifugal switch is stuck in the run position, the motor will not start but will hum. This is the run windings. The motor will run if you spin the rotor, and make full power if correctly wired, once up to speed.

 

[1982fxr]

I have yet to be impressed by a jet Grinder...

 

[Jason280]

This is the run windings.

So, how should I proceed?

 

[Jason280]

Finally got a chance to play around with the grinder again, and tested the wires with a multimeter. I have continuity between wires 1 & 3 and 2 & 4, with resistance between the pairs being 1.2-1.3 ohms. I *guess* 1/3 and 2/4 are paired together, but not sure how I should proceed to wire up for 240v.

 

[sberry]

As a hobby concern and the risk price this may be ok especially if it is a small part or switch issue. It spins, the wheels look usable and if it really isn't broke motor its a nice grinder. If it would run 120V it would be the way to fly. My table saw is 120V at 1 hp, could be wired either way but its just not a problem getting enough power to run.

 

[sberry]

My FIL got me a big ole Baldor grinder for 50 at a sale, its still in my storage. I have a little one and really only rarely use the grinder and the wire wheel for a few bolts. I really use hand held tools, 1/4 wheel on a 4 1/2 electric and air specialty stuff include wire wheels, rotary file, minor buffing wheels. A sander. They perform same functions of so much stuff. Even rust and paint cleaning, so much faster to wire wheel, clean slag or paint than to sandblast every piece to death.
Wire wheel needs variable speed. I used to have a 9 inch grinder, broke it and don't miss the thing. The 4 1/2 is so convenient and I don't grind myself in a corner. Salvage steel is so much lighter than it was in the past, only on someone elses repair have I actually used a couple wheels at a time in years.
Like a roll of mig wire, can go a year on a spool in my bench mig, do hundreds of jobs or on a rare occasion run a pound of wire but usually resort to other means so as not to eat up my small mig materials.
You could still have to find a running machine but salvage the wheels even here. As a home user not sure why someone would actually need it without definite plans or as a hobby.
I handheld all the steel fab grinding. I actually can sharpen a twist drill with one about as good as a bench on a decent day.