# Switching, Fore And Aft



## T Bredehoft (May 15, 2015)

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.


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## gr8legs (May 15, 2015)

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


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## brino (May 15, 2015)

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


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## T Bredehoft (May 15, 2015)

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.


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## RJSakowski (May 15, 2015)

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).


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## T Bredehoft (May 15, 2015)

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.


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## randyc (May 15, 2015)

T Bredehoft said:


> 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.


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## randyc (May 15, 2015)

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


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## T Bredehoft (May 15, 2015)

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.


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## randyc (May 15, 2015)

T Bredehoft said:


> 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 !


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## T Bredehoft (May 15, 2015)

Done and done. Brino was right, on in center-off hums.  doesn't know the words.  I rewired it, undid the first attempt, put in jumpers from the red and black wires to the switch and back. It works, use the on/off switch for on and off, use the DPDT switch for forward and reverse. I was able to run a 1/4 40 tap in and out, didn't want to back it out manually.


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## RJSakowski (May 15, 2015)

Gunrunner you need to order a set of these for the Z axis hand crank. Bill did you just spit coffee on your monitor? :rofl:

View attachment 253356


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## T Bredehoft (May 15, 2015)

No monkey wrench, I've got what I want, RJ, a switch to turn the lathe on and off, and one to determine which way it will go when it starts. I  realize that one switch could do the job, as you've diagrammed, and that probably would be good for a larger machine, but my little lathe works fine the way it is and I don't have to be concerned if I'm turning it on the right way or not. One switch to turn it on.  The other one is out of sight.


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## RJSakowski (May 15, 2015)

T Bredehoft said:


> No monkey wrench, I've got what I want, RJ, a switch to turn the lathe on and off, and one to determine which way it will go when it starts. I  realize that one switch could do the job, as you've diagrammed, and that probably would be good for a larger machine, but my little lathe works fine the way it is and I don't have to be concerned if I'm turning it on the right way or not. One switch to turn it on.  The other one is out of sight.


That is the way I did my drill press.  I put a reversing switch on for the same reason that you did; I was threading a lot of 1/4-20 holes and did not want to manually back the tap out.


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## T Bredehoft (May 15, 2015)

We're looking into a product that has two 1/4 40 male/female sets, 3/4 in long in each assembly.  I will be threading them on the lathe, now I don't have to make the handle for the spindle to crank it backwards.


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