What's new
What's new

Newbie to forum and lathes


Jun 28, 2022
Hi all! Newbie to forum, newbie to metal lathes, just bought a South Bend B9 in OK/fair condition, needing some TLC, and have a motor/switch question:
Original motor - which I’d like to keep for the ‘vintage’ look - is 3-phase, wired to a drum switch for reversing capability. That was replaced with a 15A wall switch and 120V single phase motor, and I’d like to revert to ‘vintage’ motor/drum switch.

I’d appreciate recommendations on the following options:
1) Use the 3-phase drum switch to control/reverse a single-phase motor, either 120 or 240V and find a ‘vintage-era’ motor
2) Use a VFD to drive existing motor thru drum switch
3) Use drum switch to control VFD to control existing motor (idea from Home hobby machinist buy/sell/trade group on FB)
4) Use an alternative arrangement I haven’t thought of/read about that will allow forward/off/reverse via drum switch and still look vintage

I know this was long - my apologies!
The guys over at OWWM.org/electricals will be able to give you all sorts of ways to make that work. There is some sharp folks over there for that type of thing.
Just briefly, the 3 phase drum switch you have is basically a 3 pole, double throw switch with a "center-off" position.

It can control a three phase motor directly, it can control a single phase motor for forward/reverse operation IF the motor you pick can be reversed. Not all single phase motors can be reversed.

It can control a 3 phase motor under VFD control but NOT DIRECTLY. You can use the switch to perform the logic-level things you need to do to start, stop, or reverse inputs to the VFD to get the motor to do what you want.

You cannot use a VFD to control a single phase motor that has a starting switch and winding in it.
Without getting too deep into the actual wire connections, conceptually, a single phase motor which has a starting winding and starting switch (the most common kind used for machinery like lathes) runs in either the forward direction or reverse direction depending upon how the start winding is connected across the incoming line connections. Reversing the direction of rotation is simply a matter of reversing the connection of the start winding. This is almost exactly the same as the case with the 3 phase motor where reversing the motor is simply a matter of reversing two of the 3 phase connections. The rotary drum switch is very good at doing that.
Thanks! I realized after posting that this question - at least the wiring part - has been ‘rode hard & put up wet’ on this forum… sorry I didn’t look first, but I’m an old fart who doesn’t typically follow rules well.
I’m interested in responses to the other options, though!