Switching, Fore And Aft

[T Bredehoft]

My Clausing/Atlas 6 x 24 Mark II lathe has a Westinghouse 1/3 horse, 115 Volt 6.3 Amp motor. Its ID tag says "For CW Rot., Interchange Red and Black" I understand that this means I can reverse the motor by switching these two connectors. The off/on switch is currently a small toggle switch, commonly noted as 15 amp.

My question is....Can I use a similar double pole double throw (center off) switch to reverse the motor? If so, what size wire would be best for these connections?

Thanks.

 

[gr8legs]

Yes and No. Sounds like your motor is a split-phase and the direction of rotation is determined by the phase relationship of the 'start' and 'run' windings when power is applied to a stopped motor. The 'start' winding is disconnected as soon as the motor gets to about 33% of rated speed and you have to let it come to a stop to reverse it.

The red and black wires are probably the 'run' winding so if you want one switch for Reverse-Off-Forward selection you will need a 3PDT switch. Two of the poles reverse the Black and Red leads, the third interrupts all power to the motor.

You could use two switches, one for Forward-Reverse and the other for Power. You could use the DPDT center off switch you have for 'forward-reverse' but I recommend against it as turning on the 'Power' switch with the 'Forward-Reverse' in the center position will put line voltage across the 'Start' winding and could release the magic smoke if sustained. If using two switches, don't use the center-off variety.

As far as wire size, as short as these connections will be, anything 18-gauge or larger should be fine. I would use stranded wire for its vibration tolerance but that's your call.

Stu

 

[brino]

Hi Tom,

I'm not clear if your asking:
1) can I use the third position of the current on/off switch for reverse, or
2) can I add another switch like the current on/off switch to control direction

Here's what I did on my old lathe. One rocker switch for on/off, a second for fwd/rev.
Each switch had only two positions.
Just remember the direction switch only works when the motor is off. That "start" winding is meant to give the initial kick in a particular direction.
That is, if you need to change direction you need to turn it off first and wait 'til it stops, then flip the direction switch, then turn it back on.

Forget the centre-off position for the direction switch, if you leave it in the centre and turn it on then it won't start up, it'll sit there humming and getting hot! I'd just use a double-pole, double-throw(DPDT), two position switch for direction.

I cannot guess at wire size. I usually take the safe path and use the same gauge wire as the run windings.

-brino

 

[T Bredehoft]

Thank you both for your replies. My Ames turret lathe is wired with two switches, I didn't realize the three pole need. I'll keep the On/Off switch, using it to power the direction switch, ignoring the center off position.

Its good to have a handy source for questions, glad this forum is here.

 

[RJSakowski]

You can reverse either a capacitor start or a capacitor run motor by simply reversing one of the two windings. (You can start a capacitor start motor by spinning by hand; it doesn't need the start winding to run) A double pole double throw, center off switch will work nicely for either. No need for a second switch. If you don't have a center off switch, you would need the second switch. A three pole switch will not help you. You need three positions (Off, On (CW), On(CCW).

 

[T Bredehoft]

Well, I wired it by putting a DPDT switch between the on off switch and the motor, it goes forward in both positions. Subsequent to RJ's post, above I tried using ctr off for off, it still doesn't reverse..... I'm a toolmaker, not a spark chaser, I await further suggestions.

 

[randyc]

Well, I wired it by putting a DPDT switch between the on off switch and the motor, it goes forward in both positions. Subsequent to RJ's post, above I tried using ctr off for off, it still doesn't reverse..... I'm a toolmaker, not a spark chaser, I await further suggestions.

Tom, are you letting the motor come to a complete stop before reversing the switch ? Bob's suggestion in post #5 should have worked. The DPDT switch must also have an "off" position as he noted.

 

[randyc]

Switch wiring. The AC lines are connected to the two switch center positions (I forgot to draw them on the sketch):

 

[T Bredehoft]

Here it is, (I hope), The admonition to reverse the red and black wires applies to the red and black wires, not the power (input 120 v) wires. I'm not sure I'm up to working inside the motor, connecting jumpers to the red and black wires.... More thought needed, I guess.

 

[randyc]

Here it is, (I hope), The admonition to reverse the red and black wires applies to the red and black wires, not the power (input 120 v) wires. I'm not sure I'm up to working inside the motor, connecting jumpers to the red and black wires.... More thought needed, I guess.

My bad - you're absolutely right Tom and my sketch would be for reversing a D.C. motor Your original plan is correct and any size wiring 12 AWG or lower is more than adequate. Sorry about the misunderstanding !