Adjustable Jazz Bass pole pieces - how do they do it?

[tonemonkey]

I want to start making bass pickups and I want all of mine to have adjustable pole pieces. In regular Jazz pups the pole pieces are the magnets, right? How could I use screws for pole pieces instead so the pole pieces were adjustable?

[David Schwab]

In pickups like the DiMarzio Model J, the poles are hex key screws, like set screws. They thread right through the plastic bobbins into a steel keeper, and have two ceramic magnets on the bottom. On the two magnets, the same pole is facing he keeper on both sides.

Here's the underside of a Model J.



This is a split humbucker, so each half has opposite polarity magnets.

The adjustable poles would probably not work very well with fiber bobbins because the wire will wind around the poles.

You can get plastic bobbins here:

Guitar Pickup Bobbins - Guitar Parts USA

They are a little shallower to allow room for the magnets on the bottom.