Machinery Repairman

Figure 7-20.—Section through a dividing head showing the worm, worm wheel, and worm shaft.
be indexed, the dividing head spindle would make
1/400,000 of a turn, or 3.24 seconds of a degree.
You can get any whole number of divisions up to
and including 60, and hundreds of others, by using
only the large index plate and the crank. The dividing
head manufacturer provides tables listing many of the
settings for specific divisions that you may read
directly from the table without further calculations. If
the number of divisions required is not listed in the
table or if there are no tables, use the manufacturer’s
manual or other reference for instructions on how to
compute the required settings.
ADJUSTING THE SECTOR ARMS
To use the index head sector arms, turn the
left-hand arm to the left of the index pin, which is
inserted into the first hole in the circle of holes that is
to be used. Then, loosen the setscrew (C, fig. 7-19)
and adjust the right-hand arm of the sector so that the
correct number of holes will be contained between the
two arms (fig. 7-21). After making the adjustments,
lock the setscrew to hold the arms in position. When
setting the arms, count the required number of holes
7-17
Figure 7-21.—Principal parts of a late model Cincinnati
universal spiral index head.