We show at Fig. 59 a portion of Fig. 58,
enlarged four times, to show certain portions of our delineations more
distinctly. If we give the subject a moment's consideration we will see
that the length of the prong _E_ of the lever fork is limited to such a
length as will allow the jewel pin _D_ to pass it.
HOW TO DELINEATE THE PRONGS OF A LEVER FORK.
[Illustration: Fig. 58]
[Illustration: Fig. 59]
To delineate this length, from _B_ as a center we sweep the short arc
_f_ so it passes through the outer angle _n_, Fig. 59, of the jewel pin.
This arc, carried across the jewel pin _D_, limits the length of the
opposite prong of the fork. The outer face of the prong of the fork can
be drawn as a line tangent to a circle drawn from _A_ as a center
through the angle _n_ of the jewel pin. Such a circle or arc is shown at
_o_, Figs. 58 and 59. There has been a good deal said as to whether the
outer edge of the prong of a fork should be straight or curved.
To the writer's mind, a straight-faced prong, like from _s_ to _m_, is
what is required for a fork with a single roller, while a fork with a
curved prong will be best adapted for a double roller.
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