DIY Demagnetising tool that works

[tonyfoale]

It is now 3 years since I made my version inspired by Mark's. I made a stand alone version with the rotor driven by an old washing machine pump motor. The motor and switch are encased in a plastic junction box and sit on a bench permanently. It gets used regularly. I am still at a loss to understand how calipers get magnetised but they do, although not often.