I have been looking around for a cheap magnetic chuck, (or power supply for the one I’ve already got) so that I could put my surface grinder to use. I ran across this one at the CAMS Yard Sale really cheap, and bought it to play around with. Its a permanent magnet type, and I was told it was a little weak. There is an Allen bolt on the side which operates a cam that releases the magnet. The action of the cam was stiff, and the mag didn’t seem to release. I figured it couldn’t be all that hard to fix.