Bench grinder, 110/220?? wired up properly according to diagram on grinder, just turns on as soon as it's plugged in but it just humms, it does not spin the grinding wheel.it is a monster w/ a 3/4 hp motor, 8'' wheel dayton bench grinder, model 4z909c

There are some images in the link, but you might have to write to China and ask.

https://www.google.com/search?q=king+bench+grinder+wiring+diagram

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Hello Kenny
What you are saying is you have a plug with wires on there already and it have Black, White and Green?
Green is the Ground wire and it will connect to the green wire on your bench grinder.
Black will go to Black on your grinder - it is the hot wire.
This leaves Red to white wire on your plug.
NOTE: is the wires on your plug the same size as your bench grinder wire or larger? If the plug wires are smaller - then go buy just a plug and connect the grinder wires directly into the plug.
Green to Ground green screw or round terminal.
Normally Black wire goes to Brass screw = both words start with the letter "B"

Contact Power Pro Craft directly to request the wiring diagram.

when i turn on switch it just humms. 1/2 hp older model

It sounds like the capacitator might be bad or the starter windings. What you can try and BE CAREFUL is turn the switch on and spin the wheel by hand in direction it will be running to see if starts. Again BE CAREFUL

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_

Replacement should be simple. Just do a one for one hookup with the new part, after you unplug it first.
For a diagram go to;

http://www.searspartsdirect.com/partsdirect/getSubComp.pd?modelNumber=397.1949&productCategoryId=0721000&brandId=0247&modelName=CRAFTSMAN-1%2F2-H.P.-GRINDER&diagramPageId=00001&documentId=00023041&pop=flush

Go to;
http://www.searspartsdirect.com/partsdirect/getSubComp.pd?modelNumber=152.211521&productCategoryId=0721100&brandId=0247&modelName=GRINDER&diagramPageId=00001&documentId=P0410025&pop=flush


and click on "View full size" at the top.

Hi again, OK, Well since I don't have a wiring diagram and the colors don't help. I am also going to assume it is 110VAC. The larger wires are probably the run or primary, it you remember which ones were connected it will help with polarizing. ( getting it to run in the right direction as well as the start and primary working together). You can use the two terminal switch but you should use a three wire cord. Use the switch to break the neutral and ground the case. The connections should be as follows: Connection 1, would have one of the primaries and one of the starts to neutral. Connection 2, the other start to the relay. Connection 3, the coil side of the relay to the remaining primary. ( if the relay has two connections on one end and one on the other it would be the single) Connection 4, the 3rd position on the relay to hot. That is how a split phase is wired. You may find a simple wiring diagram on the net if you type split phase motor wiring diagram. Good Luck to you, this should Fixya!