from the fact that experience has demonstrated that it is the most
practicable and efficient form so far devised or applied. Subsequently
we shall take up the subject of jewel pins of different shapes.


HOW TO SET A JEWEL PIN AS IT SHOULD BE.

Many workmen have a mortal terror of setting a jewel pin and seem to
fancy that they must have a specially-devised instrument for
accomplishing this end. Most American watches have the hole for the
jewel pin "a world too wide" for it, and we have heard repeated
complaints from this cause. Probably the original object of this
accommodating sort of hole was to favor or obviate faults of pallet
action. Let us suppose, for illustration, that we have a roller with the
usual style of hole for a jewel pin which will take almost anything from
the size of a No. 12 sewing needle up to a round French clock pallet.

[Illustration: Fig. 65]

We are restricted as regards the proper size of jewel pin by the width
of the slot in the fork. Selecting a jewel which just fits the fork, we
can set it as regards its relation to the staff so it will cause the
pitch circle of the jewel pin to coincide with either of dotted circles
_a_ or _a'_, Fig. 65. This will perhaps be better understood by
referring to Fig. 66, which is a view of Fig. 65 seen in the direction
of the arrow _c_. Here we see the roller jewel at _D_, and if we bring
it forward as far as the hole in the roller will permit, it will occupy
the position indicated at the dotted lines; and if we set it in (toward
the staff) as far as the hole will allow, it will occupy the position
indicated by the full outline.