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Author Topic: Grinder repair  (Read 229 times)

mattsz

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Grinder repair
« on: January 12, 2015, 05:30:25 PM »
Ok you 'lectrical smarties...

I've got an old Craftsman "1/4 Horsepower Grinder": 2.5 Amps, 125 volts, 60 Hz.  It won't run.  When I turn it on, it just hums loudly, and occasionally seems to try to turn with just a small bump of the wheels - and when it does, it seems as if sometimes they bumps one direction, and sometimes the other.

The wheels spin freely with no resistance, in either direction, whether the power is on or off, even when it's humming loudly.

Any ideas of what to check for?  Or is it a paperweight?

Here's a pic of the panel - gosh, I hope that's not blood!

DanB

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Re: Grinder repair
« Reply #1 on: January 12, 2015, 06:35:22 PM »
Hi Matt, I'd check the start capacitor/ circuit. Doesn't sound like the bearings are gone. Could be a motor winding issue, but start with the cap. Sears may have a diagram online for it with parts list.
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High On Octane

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Re: Grinder repair
« Reply #2 on: January 12, 2015, 06:46:43 PM »
Sounds like the brushes are toast.  Not too difficult to replace, and being Craftsman, you should be able to buy replacement brushes for cheap from Sears.
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Grant Borden

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Re: Grinder repair
« Reply #3 on: January 12, 2015, 07:32:23 PM »
Mattz,

I had the same symptoms with my 1968 purchased Craftsman grinder, the start capacitor had finally given up. Just don't make things to last a life time anymore.

Grant 
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mattsz

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Re: Grinder repair
« Reply #4 on: January 12, 2015, 10:12:45 PM »
Thanks guys!  I'll look into those things.  It's a small unit, and even if it's not the greatest in the world, I still think it'd be useful...

I found another site where a guy was asking about a similar unit, and the responses were shockingly negative - he was wasting his time trying fix a piece of crap, and wasting their time asking for help.   :o

motorman2whel

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Re: Grinder repair
« Reply #5 on: January 12, 2015, 11:31:15 PM »
If the brushes are not completely worn out or stuck, the armature is probably shorted out :'(.   If it says "Craftsman" on it, it should have a lifetime warranty and be replaced for a new or re-man model at any Sears tool dept ;D.
« Last Edit: January 12, 2015, 11:36:36 PM by motorman2whel »

REpozer

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Re: Grinder repair
« Reply #6 on: January 13, 2015, 06:26:21 AM »
I concur with all the above .

But if all fails, ... You might get lucky by spraying some " electric parts cleaner" on the motor winding, brushes and slip rings.
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mattsz

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Re: Grinder repair
« Reply #7 on: January 13, 2015, 11:38:02 AM »
I thought Craftsman only lifetime warranted its hand tools...

Oh well, another project... ;)

tooseevee

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Re: Grinder repair
« Reply #8 on: January 13, 2015, 01:13:37 PM »
     I'll betcha the brushes are worn down to nothing also the commutator. It will need new brushes & it will need the commutator undercut & the burn pits polished out at the least.

     
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motorman2whel

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Re: Grinder repair
« Reply #9 on: January 13, 2015, 05:02:49 PM »
I thought Craftsman only lifetime warranted its hand tools...

Oh well, another project... ;)
I think your right on new stuff, but the old stuff like your grinder was warrantied. I had a old metal case craftsman drill that was my Dads, it went bad and Sears replaced it with a newer model under warranty. It's worth a try anyway all they can say is No.
« Last Edit: January 13, 2015, 05:05:04 PM by motorman2whel »

Arizoni

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Re: Grinder repair
« Reply #10 on: January 13, 2015, 10:50:01 PM »
I don't think it has any brushes.
The tag says it is an AC Split Phase motor and all of those I've seen either have a start capacitor or a set of starting coils.

You might check the electrical contacts on the start switch on the armature.  They often get badly pitted on an old motor.

There's also a fair chance of one of the starting coils shorting out.

If taking it apart, cleaning the starter switch, greasing the bearings and putting it back together doesn't fix it, toss it and go to Harbor Freight and buy a new grinder.
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grumpyed

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Re: Grinder repair
« Reply #11 on: January 17, 2015, 04:31:17 PM »
What you have described is a bad start cap.

mattsz

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Re: Grinder repair
« Reply #12 on: January 17, 2015, 04:46:44 PM »
I haven't been able to find an exact match for schematics or manuals online, but the manual from an "identical-looking" 1/3 hp unit has a parts diagram which doesn't include a start capacitor.  There is a
"starting relay" mentioned, however... I wonder if this is the problem?

DanB

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Re: Grinder repair
« Reply #13 on: January 17, 2015, 05:08:31 PM »
I think you have to open it and have a look. If it has a start relay, it will have starter windings. So, it could be the relay or the windings. Relay is easier to replace; windings, while can be repaired, will be time consuming. Just my thinking....
Suppose I were an idiot, and suppose I were a member of Congress; but I repeat myself. ... Mark Twain
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