Electromagnetic Drill Press Vise!

[bainbob]

Yeah, I kind of thought he should have used the secondary windings but since I have done no experimentation with it I figured he knew something that I didn't. It seems that 5 VDC with a huge current draw is maybe not the best way to go either, but I really don't know.

Actually the secondary winding on a microwave transformer wouldn't work. The voltage on that winding is very high so you'd need a lot more than 120 volts to do anything, even if you unwrapped half of it. The reason it draws (and needs) so much current is because of the eddy currents. Those are caused because the laminations are shorted together by his welds (and the saw cuts). The laminations are insulated from each other when the transformer is manufactured (either by paper or shellac). One other thing to note is that it won't release cleanly because there is no provision to demagnetize it when you turn it off. This is normally done by applying reverse polarity pulses, done by a magnetic chuck controller.

[Floradawg]

Actually the secondary winding on a microwave transformer wouldn't work. The voltage on that winding is very high so you'd need a lot more than 120 volts to do anything, even if you unwrapped half of it. The reason it draws (and needs) so much current is because of the eddy currents. Those are caused because the laminations are shorted together by his welds (and the saw cuts). The laminations are insulated from each other when the transformer is manufactured (either by paper or shellac). One other thing to note is that it won't release cleanly because there is no provision to demagnetize it when you turn it off. This is normally done by applying reverse polarity pulses, done by a magnetic chuck controller.

The voltage is very high because that is the voltage designed in the microwave oven. When that coil is removed one can apply whatever voltage that is desired. If I understand you, the reason his chuck requires very high current is because he sabotaged the project by shorting the laminates and thus requiring high current to overcome the increased eddy currents. I think in a carefully designed project a microwave transformer secondary coil could be used. How much voltage and current required, I don't know but I don't think it would necessarily require a very high voltage.