V A W
is an angle of 1¼°, which equals the freedom between the guard point and the roller;
g g
represents the path of the guard pin
u
for the single roller, and is drawn at the intersection of
VA
with the roller
A′ A2
is a line drawn from the balance center through that of the ruby pin, and therefore also passes through the center of the crescent. By planting a compass on this line, where it cuts the periphery of the roller, and locating the point of intersection of