# Convenient way to demagnetize a tool bit? **URL:** \ **Category:** Factual Questions\ **Created:** [August 8, 2016, 1:07pm UTC](https://boards.straightdope.com/t/convenient-way-to-demagnetize-a-tool-bit/762131 "2016-08-08T13:07:12Z")\ **Posts on this page:** 1\ **Page:** 2
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [August 9, 2016, 2:18pm UTC](https://boards.straightdope.com/t/convenient-way-to-demagnetize-a-tool-bit/762131/21 "2016-08-09T14:18:13Z")
> [@Francis\_Vaughan](#): > > You would need to get the wires quite some distance apart. The field strength of a pair drops off as the distance to the fourth power. Not only that, whilst they do form a pair, even a loose one, you can’t usefully gain the multiplication of the field that occurs with coiling the wire. The field strength goes up as the square of the number of turns so this isn’t a trivial loss. > > In order to demagnetise a ferro-magnetic object you need to place it in a field that is stronger than the field it itself is creating. This is going to require a lot of current and a lot of turns. Which is why commercial demagnetisers use a large coil wrapped around a steel core. You need to drive the object around the entire hysteresis curve and slowly drop the field strength as you do so. If you don’t get to the edges of the curve you won’t reduce the residual magnetisation. left after the field is removed. Thanks for the info. I may try demagnetizing with a split extension cord so that I can wrap just one wire around the tool bit. I have a 1500-watt space heater, so that should move a steady 12 amps through the wire. The bit is maybe 4" long, 1/2" diameter; I don’t know how many turns I can wrap around that with insulated 18-gauge wire (maybe 32 turns?), but we’ll see. If I do this, I’ll report back here with the results. [Previous page](https://boards.straightdope.com/t/convenient-way-to-demagnetize-a-tool-bit/762131.md?page=1)