Broken craftsman 1 horse power bench grinder

Hello, this is my first time on this forum so I hope I posted this to the right thread, anyway I was using my grinder like I do everyday when the item I was grinding snagged and shot through the back of my grinder. I hit the kill switch and the grinder stopped as usual, but when I went to turn it back on the grinder hummed but would not spin under its own power. It does spin when turned by hand I figure it might have had a capacitor failure so I disassembled it and found the capacitor which is a Mallory 210-260 MFD 110VAC capacitor. I can't find one like it on eBay or McMaster-carr. Could someone, please tell me where I can get one? Here are some pictures of it.

I also have a Craftsman grinder. Didn't know much or have much cash when I bought it many years ago. Still works but when it dies I won't be fixing it. Now also have several Baldor grinders and buffers. If they break (unlikely) I'll spend the time and money to fix...

L7

You can always use an external one


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I know that it's your first time, but don't be surprised if this thread is locked. You should have read the rules.
http://www.practicalmachinist.com/vb/general/machinery-discussion-guidelines-137724/
JR

I gotta commend you on the excellent pictures, it really helps.

third post down - let's see your craftsman block grinders - Page 396 - The Garage Journal Board

I'd check for bent shaft causing a short.
I'd also consider moving the discussion to owwm.org

Perhaps Sears still has parts for this grinder? Google the Sears part number that is probably on the grinder label someplace followed by the word parts and see what comes up.

Vlad

google motor start capacitor for near equivalent

eg: Item number MSC125V2

One like this ought to do. Pix not much help, could barely ID the cap pix as such.

Could also be the centrifugal start switch hanging up.

Measure the diameter and length and narrow the search parameters.

Electronic Components and Parts Search | DigiKey Electronics

Get a Grinder that costs more than $50.00, and use that POS for a shop example of what not to do. You could paint a little picture of a POS on the side of it.

R

Mike C. said:

Could also be the centrifugal start switch hanging up.

Click to expand...

What I was able to see in the picture was a current relay ( the black box with the quick disconnects on it) that is used instead of a centrfugal switch. The coil is in series with the motor and when the motor starts, the high current pulls the relay closed, connecting the start capacitor. As the motor approaches full speed, the current drops to where the relay opens, disconnecting the start capacitor. A lot of Craftsman bench grinders used this method instead of a centrifugal switch. Unfortunately you cannot check the contacts like a cenrifugal switch with an ohmmeter, because they are not closed with the motor standing still, and only close when power is applied. There is a way to test them. Disconnect all wires from the relay Connect the coil wires in series with 100Watt incandescent bulb and plug int 120vac while monitoring the relay contacts with an ohmmeter. The current through the bulb and relay should be enough to close the contacts. They should read almost zero if the relay contacts are good and the relay is working. After going through that long winded explanation, it is probably the capacitor that is bad and here is why. Start capacitors are only built to operate very briefly, when the motor starts. Any sustained connection like a centrifugal switch that does not open, will burn them out. When the OP jammed the grinder, the motor stopped turning and the current shot up to what it is when power is first applied and the motor has not started to move. The relay closed and the capacitor stayed connected until it blew. Regardless of the switching method, jamming the grinder can have the same bad result. Modern start caps are made with different materials and can be a lot smaller so finding a reolacement should be easy. The range of values is wide and not super critical A higher voltage rating does no harm. The Mouser ccatalog is a good place to look.

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Your can always grind a larger capacitor to fit in.