With our dividers set at 5", from _B_ as a
center we sweep the short arc _c_. From our arc of sixty degrees, with a
5" radius, we take five degrees, and from the intersection of the right
line _A B_ with the arc _c_ we lay off on each side five degrees and
establish the points _d e_; and from _B_ as a center, through these
points draw the lines _B d'_ and _B e'_. Now the arc embraced between
these lines represents the angular extent of our fork action.
From _A_ as a center and with our dividers set at 5", we sweep the arc
_f_. From the scale of degrees we just used we lay off fifteen degrees
on each side of the line _A B_ on the arc _f_, and establish the points
_g h_. From _A_ as a center, through the points just established we draw
the radial lines _A g'_ and _A h'_. The angular extent between these
lines defines the limit of our roller action.
Now if we lay off on the arc _f_ six degrees each side of its
intersection with the line _A B_, we define the extent of the jewel pin;
that is, on the arc _f_ we establish the points _l m_ at six degrees
from the line _A B_, and through the points _l m_ draw, from _A_ as a
center, the radial lines _A l'_ and _A m'_.
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