bridgeport drum switch

i have a phase convertor on my 1 hp bridgeport mill sometime the mill will start just like it was wired into a 3 phase line, but most of the time i have to do a double take on the switch , ( turn it on and off quick and hit it again) to get it to run, i sent the convertor back and had the company test it they said it was OK , they even gave it a update. they thought it might help but no go. could it be a bad drum switch ? or maybe the contacts need cleaning rebuilding or something any ideas welcome.

I suspect the drum switch is the culprit but you need to determine this before you decide to revamp it.

If you have some other type of 3 phase switch available, such as a 3 phase disconnect, just disconnect the motor wires from the drum switch and connect them to the disconnect. Next wire the phase converter into the disconnect. start the phase converter then throw the disconnect and your mill motor should start. If you can do this several time and with no problems then you can be sure your problem is in the drum switch. You just need a way to test the RPC and the mill motor to be sure they are both working properly.
I start my Bridgeport with a 5 hp RPC and it starts just as if it were on real 3 phase. I am using the factory drum switch wired as it came from the factory.

Bruce Norton
Kingsport, Tn

thanks, I will give it a try.