Magnets that can be machined and threaded are called Cunico (copper-nickel-colbalt) and Cunife (copper-nickel-iron). The magnet material is very ductile (meaning it can easily be drawn thin or round). The slotted end can easily be magnetized north or south polarity. If you take the adjustable magnetic pole pieces out of the pickup, make sure you make notes where each magnet goes. The best magnetic properties for Cunife are obtained in a round wire form which has been “cold reduced” and elongated in one direction. The Cunife compares favorably in magnetic properties with cast Alnico 3.