Fig. 40
The regular index change gears
are used on the swiveling gear
plate to connect with the large
index gear to give the work the
proper speed of rotation. The lead
is obtained as described on pages
58 to 63, allowing the rotation of
the work to drive the table feed
screw. Eighteen holes in the large
index gear allow indexing when
cutting multiple threads.
A rack cutting attachment or vertical spindle milling attachment is used to drive the cutter.
Spiral Milling Attachment. This attachment, shown in Fig. 40, is designed for the heavy class of spiral cutting in conjunction with the spiral head. The cutter is placed on the end of cutter spindle, allowing attachments to cover a large variety of work. In addition to cutting spirals, attachments can be used for cutting racks. The spindle can be set at any angle in a horizontal plane.
Rack Cutting Attachment. An attachment for cutting teeth in racks is shown in Fig. 41. It can also be used in connection with the spiral head for cutting worms, on Universal Milling Machines, as shown on page 173, and for other miscellaneous operations.
Fig. 41
The cutter is mounted on the end
of a hardened steel spindle that
extends through the attachment case
parallel to the table T slots. This
spindle is powerfully and smoothly
driven from the machine spindle by a
train of hardened steel bevel and spur
gears.
A vise, the construction of which can be plainly seen in the cut, is furnished as a part of the attachment.
When cutting racks, some convenient means of indexing to quickly and accurately space the teeth is
