I use a small induction motor frame, without it's armature, as a demagnetizer. I have about a 200 watt light bulb in series with the stator to limit the current. I can pass most anything up to about a 10" crescent wrench through it. Works quite well. To properly demagnetize you really need an AC field and not turn off the current until the tool is about 4 foot from the coil. We used to work on Electron Microscopes and frequently had to demag parts that some Nimrod used a magnetic screwdriver on. I despise magnetized tooling in my shop/toolbag.