Angle grinder brushes arcing

[Stan in Oly, WA]

I have a cheap 4-1/2" angle grinder which stopped running recently. I checked the brushes, which seemed okay, and put it back together. Now it runs poorly with a lot of arcing from the brushes, and the sound of continuous arcing. It's clearly a throwaway tool, and that's exactly what I'd do with it except for one thing: it's the only angle grinder I own that has a 3/8" spindle, and I still have a small stock of metal cut off disks that have 3/8" arbors.

Any suggestions about how to fix it? If it needs new brushes I'm probably sol. There's no point bothering to look for any except maybe in the box of angle grinder parts I have on hand. The other option would be to find a 5/8" to 3/8" adaptor for one of the other grinders. I have no idea about the availability or cost of that.

Thanks, Stan

 

[Ken Macfarlane]

First, was the commutator shorted out by something? That will cause problems.

For new brushes just go to the electric motor shop and they can find some close. If they are a bit big just file them down. I just put some from a dodge alternator in my Kubota hvac fan. Took a tiny bit of filing but not bad.

 

[guido]

Hello Stan in Oly, WA,

Look at the picture. Remove the edges as shown. Clean the commutator with emery cloth. For cleaning the segments, a single side safety razor blade work real well. A chain saw file works well for the concave part of the brush. Chances are the brushes have a very sharp leading edge, that is what makes them jump and arc. If you take the edges off as you see on the drawing, the tool will come alive! Make sure the spring pressure is adequate and even an both brushes.
Good Luck...............................

Guido.

 

[Bus Driver]

Significant brush arcing accompanied by slower running usually means a short in the armature windings. Run it till it quits-- which will not be long. No practical repair.

 

[pete 23]

I did a little looking around on the net and found brush's for my DeWalt this summer.

 

[Stan in Oly, WA]

Bus Driver,

You were right about that. I did what Guido suggested to the brushes, then ran the grinder until the smoke came out of it---about fifteen seconds.

For $2.49 I can get a cut-off wheel arbor for my die grinder at Harbor Freight. That will be a better use of 3" cut-off disks, anyway. On any angle grinder I can only use a cut-off disk until it's down to about 2-1/4" in diameter. Subtracting that amount, I calculated that a 4-1/2" cut-off disk provides 4 times as much useable abrasive as a 3" disk. I would expect to get better results with a die grinder.

Stan

 

[Anonymous-0]

You don't use emery cloth to clean a commutator. It has fine metal in it that will cause more arcing and damage. Use sandpaper or even a pumice stone. You can even get special stones for cleaning armatures. They use them to clean the armatures on Lincoln SA200 welders.

 

[Ultradog MN]

I quit reading at the word cheap.
Buy good tools. You can get parts for them and repair them.

 

[showcrop]

My local independently owned hardware has a drawer of various brushes.

 

[Stan in Oly, WA]

Great advice. Unsolicited, but great. I'm surprised that nobody's thought of it before.

Stan

 

[Ultradog MN]

Unsolicited?
You posted about your cheap tool and asked for help on how to fix it.
Some gave you one kind of advice. I offered another kind of advice.
In the future if you wish to recieve one type of advice and do NOT wish to recieve another type of advice please specify that in your original post. Otherwise I will continue to give the best advice I can. Which in this case is to stop buying cheap tools.

 

[Dr. Walt]

Stan:

Be real careful that your die grinder RPM doesn't exceed the RPM of the discs, the discs could fly apart during use. BTDT, I have several die grinders that exceed 45000 RPM (discs were rated at 20000 RPM) - very painful removing deeply embedded disc fragments from your flesh.

Doc

 

[baldwin racing]

not trying to be smart.....but buy the time you keep tearing the cheep grinder apart and putting it back together you can run down to local welding supply and buy a dewalt ,milwalkee, 4.5 inch grinder and have the job done......that's if you have the money to buy one or time not that valuable......if your doing a job it will be costing you time in the long run.....if you are woking at a job site......I understand you want all that you can get out of a tool we all do. but sometimes you just need to chuck them out....good luck maybe get it all fixed up later when not needed (on a winter weekend)and keep for spare.....
kelly

 

[Stan in Oly, WA]

What you say is absolutely correct, but the issue was that I thought it was the only angle grinder I owned that had a 3/8" shaft (actually, it turns out that I have a Makita that does, too) which would allow me to use several dozen 3" metal cutoff disks I have.

It's now a dead issue for several reasons:

1. It must have had a short in the commutator, as Bus Driver warned me.
2. After I cleaned the brushes and rounded the leading edges, it burned up when I ran it.
3. I can get a cutoff disk holder for my die grinder from Harbor Freight for $2.49, an get more use from 3" cutoff disks than I would with an angle grinder, anyway.

But I don't consider it a waste of time to have posted here. I got some useable information, and I learned more about who will take the time to try to answer the actual question asked, and who won't.

Thanks, Stan

 

[Stan in Oly, WA]

Com'on Doc, real men don't mind removing deeply embedded pieces of fragmented abrasive wheel from their flesh. (I do, though.)

Thanks for the warning. I wouldn't have thought of it and might have had to find out the hard way.

Stan

 

[baldwin racing]

stan,
no I don't think is was a waste of time posting on here.....I learned some stuff myself about brushes also......lol I ment take grinder to shop put it in corner and buy a new one till you have time to work on it on a slow winter day.....
if your doing a job.....

kelly