Its Alive!

Who doesn't love a 3 day weekend, even when you have house guests.  If you ignore them, you can get a lot accomplished.  With the wife and kids running interference, I was able to sequester myself in the garage-shop several hours at a time, and Voila!, I solved the mystery of the government [read: non-working] lathe.

Because the mill was working, I believed that the switch configuration was correct.  So I had 3 phase power going at least to the end of the wires at the lathe.  My concern was that there were only 3 wires coming from the motor and one of them was green, suggesting single phase 220V with a ground.  But the motor plate clearly said 3 phase.  Further obfuscating things was the directional switch--reverse-off-forward--that was wired in the connection box  to the motor with all black wire.  But when I took the cover off the switch, I could see clearly that it was a 3 pole switch, which made the connections somewhat irrelevant except in making the reverse position actually run the motor in reverse and vice-versa, but this was only a matter of rearranging the wires after I got the lathe running, if necessary.  My next step was to look at the wiring at the motor. 

While removing the side access panel, I admired the craftsmanship that went into building the machine, down to the point of tapping the housing for the machine screws that hold the access panel in place instead of using nut and bolt.  With the panel removed and a good light, I was able to get a better look at the motor plate, which offered the critical clue as to why the motor was not running.  This is a dual voltage motor--208/220--460V.  It dawned on me that the school from which the lathe came was probably set up for 460V, so the motor was probably wired for that configuration.  All that remained was to rewire the motor for 220V (220--221, whatever it takes). 



When I removed the wire access panel on the motor, I was relieved to find the wiring diagram printed on the inside for both voltages and all the brass wire identification tags were still intact on the wire leads, so it was simply connect the dots. Once I had the motor re-wired, I fired it up and it ran perfectly.  My variable drive does work for adjusting the spindle speed, except that at too low RPM, the spindle won't turn at all. I was a little concerned that there was no ground wire, but I bonded the case to the metal conduit I have run continuously back to the sub panel, so short of running a separate conductor (which is over kill and would be a PITA), that will have to be sufficient.  But all in all, the system works as intended and I was up and running early Saturday, leaving some time to get back to work on Yoda.