During the early days of Fender they used a company called Race and Olmsted which was near the Fender plant in Fullerton, California. They used a treatment called case hardening or surface hardening of the steel bridge plates. The surface hardness of steels can be changed by a surface hardening treatment. This can give the surface of the steel a high resistance to wear and an inner core with adequate strength and toughness for the pressure of the bridge saddles. Leo felt the surface should be harder so the adjusting screws don’t cut into the surface and helps reduce the stress of the strings and the load required to hold the tension. Carburizing is also a term used for case or surface hardened steels. It is hard to drill and countersink holes in the bridge plates of most Fenders because of the case hardening. The case hardened steel was used on the early lap steels where the strings connect and ride over the edge of the bridge-pickup unit. The case hardened steel would keep the guitar strings from cutting into the steel. Many copy or replacement bridges made of plated brass will suffer from height screw depressions in the metal.

Remember too that the steel plate in a Fender Telecaster affects the magnetic field from the pickup and gives the Telecaster, Esquire and Broadcaster that cutting sound. The bridge cover on Albert Collins Telecaster is steel and helps radiates the magnetic field throughout the bridge and strings. He’s my favorite blues player along with Roy Buchanan.