Before we proceed to delineate the exit pallet of our escapement, let us
reason on the relations of the several parts.

The club-tooth lever escapement is really the most complicated
escapement made. We mean by this that there are more factors involved in
the problem of designing it correctly than in any other known
escapement. Most--we had better say all, for there are no exceptions
which occur to us--writers on the lever escapement lay down certain
empirical rules for delineating the several parts, without giving
reasons for this or that course. For illustration, it is an established
practice among escapement makers to employ tangential lockings, as we
explained and illustrated in Fig. 16.

Now, when we adopt circular pallets and carry the locking face of the
entrance pallet around to the left two and a half degrees, the true
center for the pallet staff, if we employ tangent lockings, would be
located on a line drawn tangent to the circle _a a_ from its
intersection with the radial line _A k_, Fig. 21. Such a tangent is
depicted at the line _s l'_. If we reason on the situation, we will see
that the line _A k_ is not at right angles to the line _s l_; and,
consequently, the locking face of the entrance pallet _E_ has not really
the twelve-degree lock we are taught to believe it has.

[Illustration: Fig. 21]

We will not discuss these minor points further at present, but leave
them for subsequent consideration. We will say, however, that we could
locate the center of the pallet action at the small circle _B'_ above
the center _B_, which we have selected as our fork-and-pallet action,