If the angle _k'_ of the tooth _k_ in Fig. 84 was
extended outward from the center _A_ so it would engage or rest on the
locking face of the entrance pallet as shown at Fig. 84, then the draw
of the locking angle would not be quite fifteen degrees; but it is
evident no lock can take place until the angle _a_ of the entrance
pallet has passed inside the circle _s_. We would say here that we have
added the letters _s_ and _t_ to the original drawings, as we have
frequently to refer to these circles, and without letters had no means
of designation. Before the locking angle _k'_ of the tooth can engage
the pallet, as shown in Fig. 84, the pallet must turn on the center _C_
through an angular movement of at least four degrees. We show the
situation in the diagram at Fig. 86, using the same letters of reference
for similar parts as in Fig. 84.
[Illustration: Fig. 86]
As drawn in Fig. 84 the angle of draft _G a I_ is equal to fifteen
degrees, but when brought in a position to act as shown at _G a' I'_,
Fig.
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