Funny - I've been fooling with using a large dia AC excited coil to see how much it takes to demagnetize 4130 steel. It seems to take about 30 ampere-turns in free air to generate enough magnetic flux to reset everything as the 4130 steel is pulled away slowly.

The next step inder personal consideration is to take a 100 ft coil of 3 conductor #14 Romex wire, roll it into a 1 ft dia coil, splice the ends together so that the whole mess of wires is in series, and excite that with a Variac with a few volts to get ~ 4 amps of current thru it. Of course you could use a 500 Watt series heating element to limit the current to 3-4 amps too.

Or a long extension cord of say 100 ft of # 16 - cobble a suicide plug system to series the three wires & bring a power cord out.

This is all strictly not UL approved.

Operation would be to hold it near the area to be degaussed and slowly withdraw it to at least 5 to 10 feet away before taking the power off.

Has anyone else fooled with this sort of approach? and how much will a compass take before it becomes demagnetized? or a tachometer? or a magneto (much more I'd think).