work.

[Illustration: Fig. 41. New Britain Multiple-spindle Automatic Chucking
Machine of Single-head Type]

When a single-head machine is in operation, the turret advances and
feeds the work against the revolving tools so that a number of pieces
are operated upon at the same time. The turret is fed by a cam drum _B_.
Cam strips are bolted to the outside of this drum and act directly
against a roller attached to the yoke _C_ which can be clamped in
different positions on the spindle _D_, the position depending upon the
length of the work. On the opposite end of the turret spindle is the
indexing mechanism _E_. An automatically spring-operated latch _F_
engages notches in the rim of the dividing wheel, thus accurately
locating the turret. The turret is locked by a steadyrest _G_, which,
for each working position, automatically slides into engagement with one
of the notches in the turret. This relieves the indexing mechanism of
all strain.

[Illustration: Fig. 42. Detail View of New Britain Double-head
Eight-spindle Machine, Boring, Reaming and Facing Castings]

This type of machine is also built with two spindle heads, the
double-head design being used for work requiring operations on both
ends. When the double-head machine is in operation, the revolving
spindles and tools advance on both sides of the chuck turret, the latter
remaining stationary except when indexing. The feed drums on the
double-head machine are located directly beneath each group of spindles.

Fig. 42 shows an example of work on a machine of the double-head design.
This is an eight-spindle machine, there being two groups of four
spindles on each side of the turret. The castings _E_ are for the wheel
hubs of automobiles. The order of the operations on one of the castings,
as it indexes around, is as follows: The hole in the hub is first
rough-reamed by taper reamer _A_ and the opposite end of the hub is
rough-faced and counterbored by a tool in spindle _A_{1}_. When the
turret indexes, this same casting is reamed close to the finished size
by reamer _B_ and the left end of the hub is rough-faced by cutter _F_,
while a tool in the opposite spindle _B_{1}_ finishes the counterboring
and facing operation. At the third position, reamer _C_ finishes the
hole accurately to size, and when the work is indexed to the fourth
position, the hub on the left side is finish-faced by a tool in spindle
_D_. (The third and fourth spindles of the right-hand group a