The passing hollow _E_ is located
and defined by drawing the radial line _B c_ from the center _B_ through
the intersection of radial line _A i_ with the dotted arc _b_, which
represents the pitch circle of the safety roller. We will name this
intersection the point _l_. Now the end of the guard point _C_
terminates at the point _l_, and the passing hollow _E_ extends on _b_
sixteen degrees on each side of the radial line _B c_.
[Illustration: Fig. 82]
The roller action is supposed to continue through thirty degrees of
angular motion of the balance staff, and is embraced on the circle _a_
between the radial line _B k_ and _B o_. To delineate the inner face of
the horn _p_ of the fork _F_ we draw the short arc _g_, from _A_ as a
center, and on said arc locate at two degrees from the center at _B_ the
point _f_. We will designate the upper angle of the outer face of the
jewel pin _D_ as the point _s_ and, from _A_ as a center, sweep through
this point _s_ the short arc _n n_.
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