In the drawing shown at Fig. 20 the radius of this curve was obtained by
taking eleven and a half degrees from the degree arc of 5" radius in the
dividers, and setting one leg at the intersection of the radial line _A f_
with the arc _i_, and placing the other on the line _i_, and allowing
the point so established to serve as a center, the arc was swept for the
back of the tooth, the small circle at _n_ denoting one of the centers
just described. The length for the face of the tooth was obtained by
taking eleven degrees from the degree arc just referred to and laying
that space off on the line _p_, which defined the face of the tooth. The
line _B k_ is laid off one and a half degrees below _B h_ on the arc
_m_. The extent of this arc on the arc _d_ defines the locking face of
the entrance pallet. We set off four degrees on the arc _m_ below the
line _B k_, and through the point so established draw the line _B l_. We
draw a line from the intersection of the line _A g_ with the line _c h_
to the intersection of the arc _e_ with the line _c l_, and define the
impulse face of the entrance pallet.
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