Magnetising or demagnetising tools: how to do it

Magnetise a screwdriver by stroking it 20 to 30 times in one direction with a strong magnet, from the handle to the tip. Demagnetise it with a (de)magnetiser block or by moving it back and forth with decreasing force. Only steel can be magnetised.
By Magnetenspecialist
2 min read

Short answer: you magnetise a screwdriver, bit or needle by stroking it 20 to 30 times with one pole of a strong magnet, always in the same direction, from the handle to the tip. Lift the magnet well away in between strokes. Demagnetise with a (de)magnetiser block, or by slowly pulling the tool through an alternating field. It only works on steel. Hard tool steel retains the magnetism for a long time; soft iron loses it quickly.

Magnetising in 4 steps

  1. Take a strong neodymium magnet, for example a disc magnet Ø15 x 5 mm or larger.
  2. Place one pole against the shaft near the handle.
  3. Stroke the magnet in one movement to the tip. Then lift the magnet well away from the steel and start again at the handle.
  4. Repeat 20 – 30 times. Test with a small screw.

Why it works: the magnetic domains in the steel align with the field of the magnet, and in hard steel most of them stay that way. See how does a magnet work?

Demagnetising

  • With a magnetiser/demagnetiser block: pull the tool through the opening marked "demagnetise" and move it slowly away.
  • With a magnet: stroke in the opposite direction with less and less force, or slowly rotate the tool while removing the magnet. This is less precise.
  • With an alternating field: professionally, this is done with a demagnetising coil on alternating current.
  • With heat: above approx. 770 °C steel loses its magnetism (Curie point), but that ruins the hardening of tools. Don't do it.

A stronger solution: a magnet on the bit

A magnetised screwdriver only holds weakly. A small ring magnet over the bit or a magnet in the bit holder holds a screw much more firmly. See the ring magnets.

Frequently asked questions

Can I remagnetise a neodymium magnet with another magnet?

No. Neodymium has a very high coercivity and needs a magnetiser of more than 3 Tesla. See why do magnets lose their strength?

Is a magnetic screwdriver bad for electronics?

For modern electronics, the weak field of a magnetised screwdriver is not a problem. For mechanical watches and compasses, it is better to use non-magnetised tools. See magnets and electronics.

Can I magnetise stainless steel tweezers?

Only if they are made of magnetic stainless steel (such as 410 or 420). Stainless steel 304 or 316 cannot be magnetised. See is stainless steel magnetic?