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Can anyone show me a wiring diagram from a 1/2 hp 4 pole AC motor to a drum type reversing switch, on a old Atlaslathe? Answered

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The simplest solution, if you can't figure out how to reverse that motor, may be to replace it with a motor that *is* reversable.

(I have an old Sears drillpress which has a motor that can be reversed by swapping the connections to two terminals; I wired that to a DPDT switch so I can control the direction without having to rewire. I also have a table saw from the same period, with a motor that has about the same power, which does *not* have that feature... not that there's be much use for it on a saw, of course. Point is, some do, some don't, and if yours doesn't you might want to look for one that does.)

Is it even reversable?  Most ac motors are not.

Actually most ARE ! Its a question of phasing the windings correctly.

BRUSHED AC ones can be problematic, but induction motors are always reversible

Steve

I did not know that!  I've seen a few that had terminals marked to reverse rotation.  So if terminals are not marked for reverse rotation, you have to "rewire" or what?

I always thought the same - that ac motors of some types always start in a random direction - like microwave turntables or other small ones...surely theres a logic to how the coils force it to go a particular direction.

JFYI

REAALLLy cheap AC motors don't start preferentially, but they often have a kick spring to push them the way they need to go.

Slighly less cheap one "shaded pole" motors have a shorted turn that shapes the magnetic field slightly so the motor starts in one dirction, at the cost of wasted heat.

There we go - otherwise it would need a smart exciter circuit to use the correct coils in the right order to begin with - like a brushless dc.

.  FWIW, the only microwave I took apart had a mechanical "toggle" that flopped around and reversed the turntable.

Try a Google search.  There seem to be a lot of resources out there for Atlas lathes (two words, not one).  If you know the model number you will have a lot more success.