After studying carefully
the instructions just given we think the workman will have no difficulty
in selecting a cylinder of the right diameter.
MEASURING THE HEIGHTS.
The next thing is to get the proper heights. This is much more easily
arrived at: the main measurement being to have the teeth of the escape
wheel clear the upper face of the lower plug. In order to talk
intelligently we will make a drawing of a cylinder and agree on the
proper names for the several parts to be used in this chapter. Such
drawing is shown at Fig. 171. The names are: The hollow cylinder, made
up of the parts _A A' A'' A'''_, called the shell--_A_ is the great
shell, _A'_ the half shell, _A''_ the banking slot, and _A'''_ the small
shell. The brass part _D_ is called the collet and consists of three
parts--the hairspring seat _D_, the balance seat _D'_ and the shoulder
_D''_, against which the balance is riveted.
[Illustration: Fig. 171]
The first measurement for fitting a new cylinder is to determine the
height of the lower plug face, which corresponds to the line _x x_,
Fig.
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