THE OUTER DIAMETER OF THE CYLINDER.
[Illustration: Fig. 129]
To define the remainder of the form of our escape-wheel tooth we will
next delineate the heel. To do this we first define the outer diameter
of our cylinder, which is the extent from the point _n_ to _c_, and
after drawing the line _n c_ we halve the space and establish the point
_x_, from which point as a center we sweep the circle _w w_, which
defines the outer circumference of our cylinder. With our dividers set
to embrace the extent from the point _n_ to the point _c_ we set one leg
at the point _b_, and with the other leg establish on the arc _k_ the
point _h_. We next draw the line _b h_, and from the point _b_ draw the
line _b f_ at right angle to the line _b h_. Our object for drawing
these lines is to define the heel of our escape-wheel tooth by a right
angle line tangent to the circle _w_, from the point _b_; which circle
_w_ represents the curve of the outer circumference of the cylinder. We
shape the point of the tooth as shown to give it the proper stability,
and draw the full line _j_ to a curve from the center _A_.
Pages:
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231