1½". The needle should be annealed and flattened a little, to give a
pretty good grasp to the notch _a_ on the pallet staff.

Good judgment is important in making this clamp, as it is nearly
impossible to give exact measurements. About 1/40" in width when seen in
the direction of the arrow _j_ will be found to be about the right
width. The spring _B_ can be made of a bit of mainspring, annealed and
filed down to agree in width with the part _A_. In connection with the
device shown at Fig. 71 we need a movement-holder to hold the movement
as nearly a constant height as possible above the bench. The idea is,
when the clamp _A B_ is slipped on the pallet staff the index hand _A'_
will extend outward, as shown in Fig. 72, where the circle _C_ is
supposed to represent the top plate of a watch, and _A'_ the index hand.


HOW THE ANGULAR MOTION IS MEASURED.

[Illustration: Fig. 72]

Fig. 72 is supposed to be seen from above. It is evident that if we
remove the balance from the movement shown at _C_, leaving power on the
train, and with an oiling tool or hair broach move the lever back and
forth, the index hand _A'_ will show in a magnified manner the angular
motion of the lever. Now if we provide an index arc, as shown at _D_, we
can measure the extent of such motion from bank to bank.

[Illustration: Fig. 73]

[Illustration: Fig. 74]