a steel shell which must be accurately finished to a slight
taper, both inside and out, threaded and plain recesses are required at
the ends, and, in addition, one or two minor operations are necessary.
This work is done in the Hartness flat turret lathe, built by the Jones
& Lamson Machine Co. The shells are turned from cold-drawn seamless
steel tubing, having a carbon content of 0.20 per cent, and they are
finished at the rate of one in nine minutes. The tubing comes to the
machine in 12-foot lengths, and the tube being operated upon is, of
course, fed forward through the hollow spindle as each successive shell
is severed.

[Illustration: Fig. 23. First Operation on Shell Illustrated in Fig.
22--Rough-turning and Boring]

In finishing this shell, five different operations are required. During
the first operation the shell is rough-bored and turned by one passage
of a box-tool, Fig. 23, and the recess _A_, Fig. 22, at the outer end,
is finished to size by a second cutter located in the boring-bar close
to the turret. The turret is then indexed to the second station which
brings the threading attachment _G_ into position, as shown in Fig. 24.
After the thread is finished, the recess _B_, Fig. 22, is turned by a
flat cutter _K_, Fig. 25. The inner and outer surfaces are then finished
to size by a box-tool mounted on the fourth station of the turret and
shown in position in Fig. 26. The final operation, Fig. 27, is performed
by three tools held on an auxiliary turret cross-slide, and consists in
rounding the corners at _b_ and _c_, Fig. 22, and severing the finished
shell.

[Illustration: Fig. 24. Second Operation--Cutting Internal Thread]

One of the interesting features connected with the machining of this
shell is the finishing of the inner and outer tapering surfaces. The
taper on the outside is 3/32 inch Per foot, while the bore has a taper
of only 1/64 inch per foot, and these surfaces are finished
simultaneously. The box-tool employed is of a standard type, with the
exception of an inserted boring-bar, and the taper on the outside is
obtained by the regular attachment which consists of a templet _D_ (Fig.
23) of the required taper, that causes the turning tool to recede at a
uniform rate as it feeds along. To secure the internal taper, the
headstock of the machine is swiveled slightly on its transverse ways by
the use of tapering gibs. By this simple method, the double taper is
finished to the required accurac