"Donuts" around magnets in vintage Fender pickups

[David King]

I never get these artifacts. I drill .187 for a .1875 rod and the magnets press in nicely and stay put with or without glue. I'm not really sure why we're even discussing this. Are these here donuts good or bad??

[David Schwab]

Leo didn't drill or glue anything. He wanted everything fast and easy. It was all stamped and pressed in.

And with the covers on your can't see it anyway. I doubt he cared what the flatwork looked like.

[David King]

Well for those of us who don't own a laser or a stamping press I'm guessing that drilling is pretty much our only choice. I drill 4-8 layers at once so it goes quick with the locator pin on the drill press table.

[Bruce Johnson]

From a tooling and engineering viewpoint, my guess is that Fender did that intentionally. They cut small rounded counterbores into the tops of the holes of the lower die. It allows them to run looser tolerances on the stamped Forbon part; less precision on the diameter of the holes and the position/spacing of the holes. When the press fixture brings the magnet down, the fixture holds the magnet accurately lined up with the hole in the die. But if the hole in the Forbon isn't exactly the right size or location, the little counterbore gives the material someplace to go. The press pressure forces the Forbon to flow around in the counterbore, and the resulting donut is accurately lined up with the hole in the die. It essentially corrects for any errors, while also increasing the grip of the Forbon on the magnet. It's like adding a stamping and crimping operation, all in one press stroke.

You guys could do the same thing in your slow-speed manual pressing operation, but you'd need a full guided upper and lower die set. Not real difficult to make, but a little fancier than what you are doing now.

[Antoon]

Guys, thanks so much for all you posts. It is great to experience that so many of you were willing to share their thoughts on this. There is obviously a lot of skilled and experienced people here. Regarding the donuts I tend to go along with Bruce and SonnyW and it all does not seem so mysterious to me anymore.

I am not a pickup maker at all, just an enthusiastic tinkerer with my own guitar. I now realize that I probably should have posted on the Beginner/ Hobbyist sub-forum. I thought it would be fun to know how to replicate this look if desired. I searched the net before I posted here but I did not come up with something sensible. Thanks again!