I have a Cummins 1/2 hrs.bench grinder in pieces. 3 wires from the inside - Black, red, and blue. A capacitor with two male connectors on the end and a switch. How does it need to be wired?

There is a similar one on eBay, but no free ones. Cummins are known for diesel engines rather than grinders, which means someone else made it and put a Cummins badge on it. Take your pick from any of these.

https://www.google.com/search?q=8%22+Bench+Grinder+manual

They don't need much of a manual anyway, most of the content is on safety. Press switch to turn on and off, one arbor is right hand thread, the other is left hand thread.

https://www.google.com/search?q=Cummins+model+c-140+bench+grinder+manual

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the switch is a simple unit so connect a red wire ( brown or blue depending on the country) to one terminal of the switch then continue that same color wire from the other terminal
So for a mains system that uses red , black and green with yellow stripe, that would amount to red in , red out , black continuous and green/ yellow to ground on the motor

2 wires are not needed to use they are the wires of an supression capacitor on the switch then there are 2 wires from your power cable and 2 that goes to your motor that 4 you only you have to use you can also connect the 2 wires from the s-capacitor with te wires on the motor together thats is how its also correct, (but best is to remove it because its only for suppression for FM ukw radio signals and everybody has DAB+ and the change to have short-circuit is reduced.

longer wire is the positive

A suppression capacitor has 2 wires and can be have red and black wire pair, and a motor have 2 wires from the electric field to the carbonbrushes and 2 other wires from the magnetfield goes to the switch and on the same wires can be connected a parallell suppresion capacitor connected bud in most cases its not needed in practice.
The other 2 wires have to come from the powercable on the switch the most grinders to find in shops are class 2 angle grinders with double insulation, But If this is an bench grinder there must be a class 1 cable used with 3 wires to earthing a metal point on the housing. look always for the 2 square symbol its class 2 and cable has 2 wires otherwise 3 .

You could connect the wires of the switch together inside and bypass the switch. Then I would connect in the power cable a switch rated for 1 hp. You can use surface mount electrical box, with two cable connectors (one for the cable going into the grinder, the other for the cable going to the male cord end of the cable. Install a 120 volt switch inside the box (similar to the light switch in the wall). Make sure that the switch is rated for 1 hp. I would install the switch under the bench, under the grinder.

Joe

I know this is an old post, but maybe it will help others looking for information.

I have the Craftsman 1/3-HP grinder models: 397.19580 & 397.19581.

They are Split-Phase single voltage (115 V), and use a Klixon start-up current style relay - 2CR14-224.

The relay is normally open. When the large starting current in the main/run winding circuit is sensed by the the relay coil (term 3 & 4) which is in series with the main winding, the relay contacts close (term 2 & 4).

The one end of the start-up winding is connected to the main coil's BLK wire in the coil pack.

When the relay contacts close the start-up winding is energized. The start-up coil is used to provide a boost to over-come the resting inertia of the rotor.

Once the rotor reaches between 65% - 75% of operating speed, the current through the main winding circuit is reduced to the point that the relay coil cannot over come the return-springs force, acting on the relay contact arm. With the contacts open, the start-up winding is no longer energized.

This should take about 2-3 seconds, if the relay malfunctions, the high current through the start-up windings (thin wires) may be damaged.

Here is a diagram I have made.


Klixon 2CR relays are no longer available.

You may find a suitable replacement here:
http://www.herbach.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=HAR&Product_

I cleaned all the wiring connectors etc and used a 4-way extension cord with an i/o switch and thermal/arc breaker surge protector thingy. I had a piece of thick cable with a molded three prong plug which I had removed from a dead paper shredder (I think??) and connected the ground to the case (previously not connected) the black to the black and white to the white. I taped the connections and plugged the test cable into the extension thingy with its switch off and plugged it into the wall outlet. Then, with the grinder switch on, I gingerly switched on the extension thingy and the grinder (sans all moving parts) ie just the motor case and spindle (held securely in the B&D workmate) and viola(!) it worked fine and built up to very fast. I switched off the grinder switch and the motor slowed, taking an age to come to rest.
Then, I fitted a grinding wheel on the left hand thread end, tightened everything and retested, using the grinder switch to start it and it spun really fast.
Soooo, I guess the secure ground is an essential feature of a capacitor induction motor. I checked some old furnace motors that were "maturing" in the basement and they had no capacitor but only 2 wires...
I am now trying to remember which parts came off last and put it all back together. I plan to test it each time I put a part back...just in case. I hate it when you fix something on the bench and when rebuilt, it won't work...don't ask about the electric starter on the snowblower..not a happy puppy!
Please, pretty please and then some, do tell me if my "fix" is wrong and I could risk all kinds of nastiness.
Thanks,
Jenni.

The capacitor is easy to change and can be matched once you remove it by any electronics parts house.