Someone recently wrote in asking how to magnetize screw driver bits using the electrical field of a spot welder. Here was the response:

Take your screw driver bits and tape them to the arm of your spot welder so that they are laying perpendicular to the centerline of the arm. If the machine has no arm, then lay them on the secondary copper, so that they are oriented at 90 degrees to the direction of the current flow.

As the current flow through the copper the magnetic flux pattern is around the copper in a clockwise and then counterclockwise direction, in sync with the 60 Hz line frequency. It changes direction every half cycle. Don't be concerned about the direction change though, it doesn't interfere. After a while the flux lines that are going the same direction as the longitudinal axis of the screwdriver bit will align the molecules of the steel all in the same direction, and the bit will become magnetized.

Sorry, I don't know exactly how long this takes to happen, and I'm sure there are many factors to be considered. I hope this helps out some though.

Bill Lucas T. J. Snow Co.

-- Bill Lucas (welders@tjsnow.com), December 18, 1999

Answers

At Chevy Gear & Axle, we used a Pertron weld control to DE-magnetize the 3rd member after welding a dynamic balance weight on the pinion gear. We downsloped to about .05% of the weld current, and when we tested the part for magnetism, the bearings, gears, etc had less than those parts that had been sitting on a shelf for a few months, in the earth's magnetic field. If you want to magnetize, you should remove the part at the peak of the current.

-- David Bacon (dbacon@updatetechnology.com), April 20, 2002.