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Craftsman Block Grinder electrical ?

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Goldhawg

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Bought a broken CM 1/2 hp block grinder for $7 at an estate sale; switch was torn apart from whoever owned it previously. So a little free time this afternoon I took off the cover and proceeded to apply 120v to see if it would spin up. applying 120V to the black wire that would go to the switch does nothing. If you apply 120V to either the red or the black lead that actually goes to the windings, the motor will humm but not spin up. When you apply the jumper to both the red & black leads going to the windings, then the grinder spins up. So--what's broken? I'm guessing just the black thing that all the wires go to? Where can I get a new switch and this piece if that is the problem?

Thx!
 

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G_P

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Is there a start or run capacitor in there?

Sent from my C5120 using Tapatalk 2
 
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Davefr

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That black box is a starting relay. It applies voltage to the start winding until the grinder comes up to speed and then it takes the starting winding out of the circuit. (It's common for these CM block grinder to use these instead of starting capacitors or centrifical starting switches)

Try to type that P/N into google and you should find a source.
 
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Goldhawg

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Davefr said:
That black box is a starting relay. It applies voltage to the start winding until the grinder comes up to speed and then it takes the starting winding out of the circuit. (It's common for these CM block grinder to use these instead of starting capacitors or centrifical starting switches)

Try to type that P/N into google and you should find a source.
Click to expand...

Thanks. PN is D8A 4CR-20-728. Google no es mi amigo. Sears no longer has this part available, nor the toggle switch, although they have a few others for this grinder.

Anybody have a good source for these grinders for parts? I'd hate to have to cannibalize one of my working 1/3hp grinders to get parts for the 1/2 hp.
 
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Goldhawg

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G

Goldhawg

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Well, I'll keep looking, but don't think I'll be able to justify new parts....
I contacted Sensata for a vendor. Found one online for $52 shipped for the relay, the next emailed me back this (ouch!):


Hi..

Unfortunately…I do not have the stock in my system

The Minimum purchase you would have to buy would be 50 pcs..

I do not think you want to do that…as the cost on each would be over $95.00 each…which is what I would charge to someone buying 500 of these..

I’m sorry…but at that price, you could buy a ton of Craftsman tools
Sorry….
Thanks,
Norm Strauss
EIS National Buyer
East Brunswick, N.J.
732-254-1451

866-207-0753 E-FAX

[email protected]

From:
Sent: Thursday, December 27, 2012 9:22 AM
Subject: Sensata relay
Could you give me a price shipped for a 4CR-20-728 starter relay made by Sensata? Sensata informed me that you were a distributor. I need one for an old Craftsman grinder. Shipped to XXXXX.
 
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Garyss.smith

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I seem to recall in one of the block grinder threads someone pointed to a company who makes those relays.
Search for block grinder
enjoy reading

Cheers

Gary
 
B

benny42

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That is a potential relay. Contact an electric motor shop near you and tell them what you need. That sort of relay is used to start refrigerator compressors too.
 
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Davefr

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Open up the relay. It could be as simple as dirty contacts.
 
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Goldhawg

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Update: Got an electrical technician friend to crack the case on the relay. He took it apart and cleaned up the mega dirty/fried contacts and I put it on tonite. The unit spins up smoothly and the light works. I used a cheapie toggle switch, but I'd like a nice one w/spade type connectors. Anybody have a good source for the on/off toggle switchs like the ones on these grinders? Lowes didn't have anything when I stopped by. The factory setup also sent T-d off the light and the grinder from one connector; are there any toggle switches that allow me to do this? Thx!

Yes I'm an electrical novice. Appreciate any help.
 
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