Help needed to repair this grinder

[saxon802]

I received this grinder which used to belong to my grandfather. Recently the motor began to only hum without turning the grinding wheel or brush. I can turn both by hand easily. What are some possible causes for it to quit working?

The grinder is a Delco model C 2351.

Thanks.

 

[Hghgrad]

Possibly brushes in the motor if its just humming.

 

[zkling]

Is that a bench grinder? Can we get a pic of the entire machine? I want to say it is a probably a bad start capacitor. You can test this by giving the wheels a good spin, then flicking the on switch. It should run. Just use caution and pay attention to where your other hand is when hitting the switch.

Edit: One thing I forgot to mention. Make sure you spin the wheels in the proper direction when you test it like I described above.

 

[saxon802]

Here is a pic of the whole grinder.

I'll test it out first as suggested before I start opening it up. Thanks.

 

[bob from indiana]

There may be a switch inside the motor connected to the start winding. If you can spin the wheel and turn the switch on to get it running turn it off and listen for a click as the wheel slows down. If you hear it there is a start switch inside. You may be able to take the motor apart and clean the switch contacts to get it back to normal. I have fixed several motors this way.
Good Luck

 

[A_Pmech]

Single-phase bench grinders are permanent split-capacitor motors. A run capacitor failure is the usual cause of starting problems

A brief paper on the subject:

http://www.wowhvac.com/tech_info/B_MARS Tech/5_Run Capacitor Basics.pdf

 

[jkherd]

Check the capacitor and the centrifugal switch adjustment to the contacts in the motor.

 

[CNGsaves]

Looks real similar to Craftsman block grinders.

Sure worth fixing / restoring that bench grinder. If you give up the ghost, don't ditch that grinder but Pay It Forward and ship to a fellow GJer.

+1 to disassemble the grinder and find your problem. Good luck.

 

[zkling]

Looks real similar to Craftsman block grinders.

Wow, thought the same thing. I wonder what the connection is? Same OEM, different end names?

 

[rsanter]

So craftsman made girders for GM????

Just kidding, sure looks like it came out of the same factory.....
It I was a Chevy guy I would have to own that.....now if someone finds one of those that says Rotunda, or FoMoCo on it......call me

Bob

 

[saxon802]

I had the opportunity tonight to work on the grinder for a while. I took off both the grinding wheel and the wire wheel. When I turned on the grinder it started slow but ran. Next i replaced the wire wheel. It started slow again and ran. When I replaced the grinding wheel and turned it on, the motor hummed until I spun the wheel. At that point the grinder seemed to tun on its own, but not as fast as I remember.

A little more checking on the grinder and as previously posted is very similar to Craftsman models 115.19500 and 397.19501, both 1/4 HP. Closer inspection of my manufacturer's plate revealed mine in a 1/3 HP grinder.

I'll spend the next several weeks cleaning, prepping and painting the grinder. I didn't notice any brushes in the motor I could easily replace. The only item I could possibly replace is the relay attached to the base plate.

 

[G_P]

There are no brushes in that kind of motor. You most likely have a bad capacitor.

 

[saxon802]

Did some more work this evening. Could not locate a capacitor anywhere. What I thought may possibly contain a capacitor looks to be only a magnetic relay. We plugged in and turned on the motor and dimmed the lights and saw no arcing. There was some slight smoking at which point we unplugged it.

Here are pictures of the relay disassembled and the motor. Any advice is appreciated.

 

[A_Pmech]

Ahh! It's a split-phase motor without a starting capacitor, using a potential relay to cut out the start winding. That's uncommon in bench grinders, in my experience.

The start windings look like they've gotten pretty hot from your photos.

 

[torqueman2002]

You can check on mfg. date, on this site --->http://vintagemachinery.org/mfgindex/default.aspx

Here's a quote from a search on Delco on ^^ site, more information available on the site. "This maker of motors and bench grinders dates back to at least 1910. They were earlier known as Dayton Engineering Laboratories Co., then the Delco-Light Co., then Delco Products Corp., and for many years was Delco Products, Division of General Motors Corp.. At some point they became part of Lincoln Electric, which is now owned by Leeson.

Delco bought Sunlight Electrical Manufacturing Co. in 1933. Delco manufactured products for Sears, Roebuck & Co.'s Craftsman line; their products have a model-number prefix of 397."

Your topic is covered in it's sister site --->http://owwm.org in the Everything Electrical section. You will need to register.

I have a Packard Electric grinder from GM.

 

[Fyrme]

So craftsman made girders for GM????

Just kidding, sure looks like it came out of the same factory.....
It I was a Chevy guy I would have to own that.....now if someone finds one of those that says Rotunda, or FoMoCo on it......call me

Bob

DELCO Products Corp. was the manufacturer of these Grinders. They sold them to Sears, badged as Craftsman and apparently badged as other brands too.

As it's been said, these are split phase motors. I wish I could offer more advice, especially since I just got done restoring one. But the motor in mine worked like it should. Sorry I can't help.

 

[zkling]

Oops, : I apologize for the mis information on the cap, I thought the smaller ones were cap start also. In that case I'd start by checking Ohms on the armature coils and then checking the start relay to make sure it fire correctly. It may be stuck and caused the start coils to overheat.

Looks like Rusty has a similar grinder.
http://garagejournal.com/forum/showthread.php?p=3200276

 

[joel63]

That's not a potential relay; it's a current relay.
But it serves the same purpose, to help to motor to start and drop out the start winding when the motor reaches approximately 75 to 80% of run speed.
Check for resistance in the normally open points. Should be close to 0 ohms.