11. The rotor must bridge the path between opposing pole pieces , but must never bridge all four simultaneously. 12. On top of the poles pieces of wood are fitted that serve as the base for the roofbeams. 13. This causes the pole-piece to wear, eventually requiring the pole pieces to be reground and recertified. 14. The second reason is that the pole pieces can make tuning and placement of the strings much more difficult. 15. A pole piece attaches to and in a sense extends a pole of the magnet, hence the name. 16. As these plants were necessarily large, they could also use large-diameter dynamos with many pole pieces . 17. The pole pieces and leads of the coils were reversed with respect to each other, producing a humbucking effect. 18. The bar-shaped magnet affects strings uniformly, without irregularities known in more traditional design with separate pole pieces . 19. The field coils now moved into short, squat " internal " coils around the pole pieces themselves. 20. The Les Paul Deluxe mini-humbucker has adjustment screws for the pole pieces ; the Firebird mini-humbucker does not.
