of 24° and draw a circle from the scape center
B
, to which the line
M M′
will be a tangent. We will utilize this circle in drawing in the faces of the other teeth after having spaced them off 24° apart, by simply putting a ruler on the locking edges and on the periphery of the circle.
We now construct
W′ A
as a tangent to the outer circle of the wheel, thus forming the lifting angle
D A W′
of 3° for the teeth; this corresponds to the angle