Install a single pole toggle switch on a bench grinder

[drmanhattan]

Hi there,

First time poster. I bought a Justen (?) 6" bench grinder from an estate sale a week ago. The person who used it last hotwired it so it runs great when plugged in. It used to have a 6amp on/off toggle switch wired to it (I know because it was kicking around the base of the grinder when I opened it up.) I tested the switch with my multimeter and it's dead. I bought a new 20amp toggle switch but when I wire the black wires to it and switch it on, it just hums? We're at the peak of my electrical knowledge so any help on how to get a switch on it would be great.

Not sure how old this grinder is (it's made in Taiwan) but there's no capacitor. Specs are: 115/230 volts; 4/2 amp; 1 phase; 60 cycle; 1/2 HP.

I can't post pictures yet but the wiring is such:

Black, red, and green wires coming from the power cord. Green is grounded via a screw terminal. Black, red, yellow, and grey wires coming from the motor.

Here's how it's hotwired:

Black wire from cord is attached to the yellow and grey wires from the motor. Red wire from cord is attached to the black and red wires from the motor.

 

[nsula_country]

We need to get your post count up so you can post a picture. Without looking at this, I am wondering if this needs a 2 pole switch? How many poles are on the existing, non-functional switch?

CT

 

[The Cobbler]

if it worked without the switch, chances are very good it's your wiring . you should have just cut the black (hot) wire to the grinder & put the switch inline.

 

[drmanhattan]

We need to get your post count up so you can post a picture. Without looking at this, I am wondering if this needs a 2 pole switch? How many poles are on the existing, non-functional switch?

CT

Yeah, I should fart around for a minute so I can add pictures.

Old switch was one pole on/off.

 

[drmanhattan]

if it worked without the switch, chances are very good it's your wiring . you should have just cut the black (hot) wire to the grinder & put the switch inline.

That's what I did? I took the black wire out of both plastic connectors, left the other wires attached as they were, then threaded both ends of the black wire through female disconnects and on to the new switch. Seemed foolproof, granted, it was my first time doing this. Even moved the disconnects to the opposite switch terminals just to see after I just got a hum the first time. Still just a motor hum?

I'll try and post pictures tonight.

 

[nsula_country]

if it worked without the switch, chances are very good it's your wiring . you should have just cut the black (hot) wire to the grinder & put the switch inline.

This.

If it worked hardwired, all that is needed it to break the circuit.

CT

 

[The Cobbler]

how many terminals are on your switch? sounds like maybe a 2 pole switch? yeah, get some pics of before & after

 

[drmanhattan]

Pics

 

[matt_i]

I bought a new 20amp toggle switch but when I wire the black wires to it and switch it on, it just hums?

Black, red, and green wires coming from the power cord. Green is grounded via a screw terminal. Black, red, yellow, and grey wires coming from the motor.

Here's how it's hotwired:

Black wire from cord is attached to the yellow and grey wires from the motor. Red wire from cord is attached to the black and red wires from the motor.

So, I would hook Black (cord) to one pole of the switch. I would land Yellow AND Gray (motor) on the other pole of the switch. Leave other wiring untouched.

OR

Wire Red (cord) to one pole of the switch. Land Black AND Red (motor) on the other pole of the switch. Leave other wiring untouched.

EDIT: I believe either of these will work BUT its safer to break the "hot" leg rather than break the neutral in the switch. How to tell: The Neutral conductor has the larger/taller blade on the male plug. Follow it or check continuity to find out which color wire jacket corresponds and then switch the OTHER one.

 

[drmanhattan]

old switch and new switch

 

[The Cobbler]

you should determine which is the hot & which is the neutral because that wire should be blk, wh, grn not blk, red, grn
then switch the hot lead with your switch
is it running now that you put it back the way it was?

 

[drmanhattan]

Thanks, Matt_i.

I'll try your ways and find the neutral wire. Appreciated.

 

[drmanhattan]

you should determine which is the hot & which is the neutral because that wire should be blk, wh, grn not blk, red, grn
then switch the hot lead with your switch
is it running now that you put it back the way it was?

Yes. It's runs when it's wired the way it is in both of the photos.

Going to try Matt_i's way.

 

[drmanhattan]

You're the man, Matt! Black into one side and yellow and grey into the other worked beautifully.

Thanks again.