Hardinge TL lathe motor question

I've got a Hardinge TL lathe that I've had around for a while but never gotten running properly.

The motor's an Allis six wire dual speed 0.75/0.375hp 220V three phase, 21W frame, type "OMS" (what's OMS?). I'm running it off 208 Y from the street, not a phase converter.

The motor runs, I can't tell if it's the right speed but it's not super slow, and it's strong enough that I can't keep it from starting by holding the sheave. It makes a buzzing noise when it runs, sounding kind of like a stalled motor, and after only about a minute of running with no load (not even a belt on the sheave) it gets hot to the touch and starts to smell hot.

Does that ring a bell for anyone? Could this be a delta motor running on Y? Motors are largely magic to me, but I'd think that if there was a broken or shorted wire somewhere then it wouldn't start, and the contacts in the drum switch look ok. What if it had been rewired for 440? That seems unlikely, but I'd expect that to just make it run weak (I assume the speed comes from the 60hz and the strength comes from the voltage). There are no obvious signs of someone having been inside the motor or electrics, but I wonder if it has wires mixed up so that some of the wires are high speed and some are low speed. I haven't chased down a wiring diagram to check it yet.

Any clues for the clueless are appreciated.

This is hardinge's typical consequent pole motor. As sold it had the wires connected to a pair of drum switches. The fwd/off/rev switch is pretty standard, but the hi/off/lo switch is pretty special.

You probably should check the motor has no shorts to ground (with all the switches in the off position and the machine completely disconnected from power) by checking between each winding and ground with a DVM that goes up to (typically) 20 megohms. Should be infinite resistance to ground from every wire. Then check five resistances, pick any wire and measure to each of the other five. Again with drum switches all off, and the meter in the lowest reading ohms range You should see three different values, if the meter has enough digits. The windings are basically a ring with six connection points around the perimeter.

Are you using the hardinge drum controllers that came with the machine?

I have a motor for that lathe if you are interested- two speed.

I run mine off a home made phase converter with no phase balancing whatsoever. Runs smooth, quiet, and cool. I also run an Elgin turret lathe with a similar motor. Lots of sudden reversing during tapping, and no unusual heating. So my point is you may have an issue with your motor or wiring.

jim rozen said:

This is hardinge's typical consequent pole motor. As sold it had the wires connected to a pair of drum switches. The fwd/off/rev switch is pretty standard, but the hi/off/lo switch is pretty special.

You probably should check the motor has no shorts to ground (with all the switches in the off position and the machine completely disconnected from power) by checking between each winding and ground with a DVM that goes up to (typically) 20 megohms. Should be infinite resistance to ground from every wire. Then check five resistances, pick any wire and measure to each of the other five. Again with drum switches all off, and the meter in the lowest reading ohms range You should see three different values, if the meter has enough digits. The windings are basically a ring with six connection points around the perimeter.

Are you using the hardinge drum controllers that came with the machine?

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Yes, has the original drum switch setup.

I'll try wadding myself up and stuffing myself into the cabinet with a multimeter. My neck hurts just thinking about it.

tom_boctou said:

Yes, has the original drum switch setup.

I'll try wadding myself up and stuffing myself into the cabinet with a multimeter. My neck hurts just thinking about it.

Click to expand...

In principle all six wires wind up in the drum switches - Although they may not be tagged with numbers as the actual motor wires are, as they will be in the motor peckerhead. Often those motors will have aluminum tags right on the wires coming out of the motor housing.

If you can identify the six motor leads where they enter the drum switch (and here it should be the hi/low switch that they land on first) you can pretty much do the ohms check there without trying to access the motor leads themselves. Besides those may have rather brittle insulation so best to not try getting into those splices.

Check to see if the wiring's been disturbed by a former owner - the mapping of the six leads to the hi/lo drum switch in particular is non-obvious and it could just have been mis-wired at some point in the past. Photos would help.