*Single phase motors, (and particularly cheap single phase motors), and cap start motors are notorious for tripping GFI outlets because they tend to generate eddy currents in their windings and induce imbalances on the conductors feeding them. They also reflect current and voltage spikes back on the feed when they switch off of the start windings. In the early days of GFI outlets, hair dryers were a big culprit. I don't know if the receptacles are less sensitive now, or if hair dryers have better motors, but it seems to have lessened greatly. I don't mean to say that lathes are restricted from the GFI circuitry. I mean to say that the purpose of GFI protection at the level of the outlet is targeted towards hand-held tools. That is why you don't see a GFI on a washing machine. It is a stationary piece of equipment, and the plug serves as it's disconnect for servicing. Same with a lathe, unless it is a little tiny bench-top model. Even then, it is a grey area.
*That was not a reference to the GFI problem. It was a reference to a seperately described situation. Go back and read the original text. (By the way, any type of imbalance of sufficient magnitude will trip a GFI, not just a "ground fault".)
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