The Alnico rod magnets used to make the pole pieces on many single coil pickups are first cast in sand. Rods are pushed into the sand removed. Then the molten magnet material is poured into each hole which is about 10″ deep. As the magnet material hardens it is removed from the sand at about a .197″ diameter. On older Fender pickups you can see the rough outer surface. Magnets on newer Fender pickups have the magnets ground to a diameter of .187″ and the surface is ground smooth. Magnets are cut to length with diamond blades and some vendors cut several magnets at a time. The cutters are similar to precision fret saws that can cut all the fret slots in a fingerboard at one time.

Magnets used in early Fenders had one end chamfered (grounded slightly) to guide the pole pieces into the flatwork (vulcanized fibre) without reaming or enlarging the holes. The chamfer would help guide the magnet rod keep the flatwork tighter to the magnets. When winding if the flatwork was loose you would have a problem with the coil changing shape as the bobbin is being wound. I have seen many tops (flatwork) pop off the pickup if it is too loose.

Magnets that look slightly rounded on each end is usually due to the magnet slugs being tumbled or deburred. This makes the ends of the magnet smoother and allows the magnet to be inserted into the flatwork easier. Magnets are tumbled because they can be done in large quantities at a time verses end grinding which is usually done one magnet at a time. When you’re making hundreds of pickups a week in production it may be necessary to find shortcuts in manufacturing.