ed to the right out of engagement,
which is its position except when cutting threads.

[Illustration: Fig. 32. Sectional Views of Quick Change-gear Mechanism]

With this mechanism, eight changes for different threads or feeds are
obtained by simply placing gear _S_ into mesh with the various sized
gears in cone _C_. As the speed of shaft _T_ depends on which of the
three gears _d_, _e_ and _f_ are locked to it, the eight changes are
tripled by changing the position of knob _K_, making twenty-four. Now by
shifting idler gear _I_, three speed changes may be obtained for gears
_a_, _b_ and _c_, which rotate together, so that the twenty-four changes
are also tripled, giving a total of seventy-two variations without
removing any gears, and if a different sized gear _s_ were placed on the
spindle stud, an entirely different range could be obtained, but such a
change would rarely be necessary. As shown in Fig. 30, there are eight
hardened steel buttons _B_, or one for each gear of the cone _C_, placed
at different heights in the casing. When lever _L_ is shifted sidewise
to change the position of sliding gear _S_, it is lowered onto one of
these buttons (which enters a pocket on the under side) and in this way
gear _S_ is brought into proper mesh with any gear of the cone _C_. To
shift lever _L_, the handle is pulled outward against the tension of
spring _r_ (Fig. 32), which disengages latch _l_ and enables the lever
to be lifted clear of the button; yoke _Y_ is then raised or lowered, as
the case may be, and lever _L_ with the sliding gear is shifted
laterally to the required position.

[Illustration: Fig. 33. Index Plate showing Position of Control Levers
for Cutting Threads of Different Pitch]

The position of lever _L_ and knob _K_ for cutting threads of different
pitches is shown by an index plate or table attached to the lathe and
arranged as shown in Fig. 33. The upper section _a_ of this table shows
the different numbers of threads to the inch that can be obtained when
idler gear _I_ is in the position shown by the diagram _A_. Section _b_
gives the changes when the idler gear is moved, as shown at _B_, and,
similarly, section _c_ gives the changes for position _C_ of the idler.
The horizontal row of figures from 1 to 8 below the word "stops"
represents the eight positions for lever _L_, which has a plate _p_
(Fig. 30) just beneath it with corresponding numbers, and the column to
the left shows whether knob _K_ shou