This point likewise represents the advance angle of the engaging tooth. Now if we measure on the arc _k_ (which represents the locking faces of both pallets) downward one and a half degrees, we establish the lock of the pallet _E_. To get this one and a half degrees defined on the arc _k_, we set the dividers at 5", and from _B_ as a center sweep the short arc _i_, and from the intersection of the arc _i_ with the line _B e_ we lay off on said arc _i_ one and a half degrees, and through the point so established draw the line _B f_.
Now the space on the arc _k_ between the lines _B e_ and _B f_ defines the angular extent of the locking face. With the dividers set at 5" and one leg resting at the point _r_, we sweep the short arc _t_, and from the intersection of said arc with the line _A c_ we draw the line _n p_; but in doing so we extend it (the line) so that it intersects the line _B f_, and at said intersection is located the inner angle of the exit pallet. This intersection we will name the point _n_.
From the intersection of the line _B e_ with the arc _i_ we lay off two and a half degrees on said arc, and through the point so established we draw the line _B g_. The intersection of this line with the arc _k_ we name the point _z_. With one leg of our dividers set at _A_ we sweep the arc _l_ so it passes through the point _z_. This last arc defines the addendum of the escape-wheel teeth. From the point _r_ on the arc _a_ we lay off three and a half degrees, and through the point so established draw the line _A j_.
LOCATING THE OUTER ANGLE OF THE IMPULSE PLANES.
The intersection of this line with the addendum arc _l_ locates the outer angle of the impulse planes of the teeth, and we name it the point _x_. From the point _r_ we lay off on the arc _a_ seven degrees and establish the point _v_, which defines the extent of the angular motion of the escape wheel utilized by pallet. Through the point _v_, from _B_ as a center, we sweep the short arc _m_. It will be evident on a moment's reflection that this arc _m_ must represent the path of movement of the outer angle of the exit pallet, and if we measure down ten degrees from the intersection of the arc _l_ with the arc _m_, the point so established (which we name the point _s_) must be the exact position of the outer angle of the pallet during locking. We have a measure of ten degrees on the arc _m_, between the lines _B g_ and _B h_, and by taking this space in the dividers and setting one leg at the intersection of the arc _l_ with the arc _m_, and measuring down on _m_, we establish the point _s_. Drawing a line from point _n_ to point _s_ we define the impulse face of the pallet.