What's new
What's new

Old bench grinder won't turn.

Status
Not open for further replies.

gdgarris

Plastic
Joined
May 19, 2012
Location
Raleigh, NC, USA
Hey everyone,

I'm new here (first post), so I'm hoping I put this thread in the right place...

I have an old Craftsman bench grinder and she seems to have given up the ghost. My father gave it to me, so I'd like to see it turn again. Its stamed Nov. 28 1968 on the baseplate and according to the faceplate it is a 1/3 horse motor that draws 3.5 amps at 115 volts. The wheels turn freely by hand, but under power it locks up and hums. It can still be turned by hand under power, but has considerably more resistance. From what I understand (which isn't much), these split phase motors are fairly simple. They consist of the motor itself, a starting relay, and a power switch. So, I've been trying to systematically determine where my trouble lies. I figure if I here a hum after flipping the switch, its getting power, so the switch is good. Then, I slapped a multimeter on the motor to check its resistance. My thinking is if I was getting next to no resistance, there may be a short somewhere in the windings. However, I'm getting something like 13 ohms. I didn't expect the resistance of a bunch of copper wire to be too high, so 13 ohms sounds reasonable to me. Also, if there was I short, I would expect the breaker to trip (which wasn't happening). So, this is telling me that it is the relay.

I've got a couple question for all of you. Is there any good method of testing a relay? If it turns out to be faulty, what are some viable replacements? I can imaging finding this specific of a relay (a Klixon 2CR-14-224) could cost me a pretty penny (probably more than a new grinder) so would there be some sort of generic replacement I could slap in there? Can you think of anything I am forgetting to test?

I appreciate the help in advance. I figure if anybody will know how to get it turning again, I'll be one of you. I've attached (hopefully) a few pictures below to give you a better idea what I'm taking about.

-Dale

DSC00761.jpgDSC00762.jpgDSC00764.jpgDSC00767.jpg
 
Check on an electric motor forum but if the unit hums likley the capacitor is shot. If it is that its a cheap quick fix.

Check to see if you can get it to spin up if you give it a start at turning.
 
If one is to check the capacitor on THIS motor, one would first have to ADD one. And the centrifugal switch that kicks it out once speed starts to ramp-up.

It left the factory with neither of those items, and is not of a sort to benefit by their addiition.

On an El Cheapo split-phase grinder (AKA misplaced kitchen vent fan motor), the more common cause of the symptoms listed is that the thrust washers (thin brass and thicker black or brown phenolic, IIRC) are worn or have split into bits and fallen out.

Result? A motor that spins freely power OFF, pulls its armature toward one end and jams. A byproduct of the field and armature never being perfectly aligned, and the price-point to which it was built not having margin for proper bearings.

Test for that by powering-ON, then pressing a bit of wood against each end of the shaft in turn to see if it frees-up and starts to turn under power.

THEN have the POS bronzed... The typical Chinese-made $49 to $89 6" and 8" grinders one finds in 'Big Box' or online are really, really, poor excuses for grinders.

But they still outperform this one.

Bill

Bill,

I believe if you research that Klixon component the OP lists you will find that it IS a cap/relay combo...pretty specialized but no longer available. Where's that bronze tank!

Stuart
 
Bill, I can't quite tell, do you think this grinder is worth salvaging? Stuart, I looked up the part and that is what I saw...wasn't too promising but I didn't know if y'all would know of an inexpensive part I could swap out to press it back into service. I'm in college and I'm trying to scrape together enough to purchase an old lathe, just wanted to try and avoid buying another piece of equipment. Just for giggles, I'll put this thing back together and see if it is the thrust washers causing the problem.

-Dale
 
Bill, didn't mean to waste "resources." Just looking for a little help, thats all. Didn't know enough about it to know if it was junk or not. Thats why I asked.

-Dale
 
Status
Not open for further replies.








 
Back
Top