the groove into the face of the steel slug (trapanning). This
groove will receive the brass that will become the outer lamination of
the bimetallic balance.
machined steel slug. The center bore is left 1mm higher than the
groove so that the final crossarm can be a maximum of 1mm thick. A
center hole is drilled prior to dismounting the slug so that it can be
centered for subsequent machining on a cement faceplate.
the OD of a brass rod to fit inside the groove of the steel slug.
The finished brass ring side by side with the machined steel slug.
Brass ring fitted into the groove of the steel slug.
brass ring has been fused to the steel slug. In essence, this is a
brazing procedure in which the brass ring is melted into the groove.
slug with the fused brass ring is machined on a cement chuck. The center
hole drilled while the slug was initally machined is used to center the
work on the cement faceplate. The slug is faced, the outer wall of
the old groove is turned away exposing the brass outer layer.
brass ring is hammered to compress the grain. This also work
hardens the brass.
Other pictures will follow. The rest of the process involves
drilling and tapping the rim for the timing screws, remounting the slug
to finish to size the OD, ID and depth of the floor (to the required
thickness of the crossarm). I will also show the
process used for cutting out the cross arm.