bar _m_{1}_. While taking these
cuts, the bars _m_ and _m_{1}_ are supported by their extension ends
which enter bushing _r_ located in the central hole of the chuck. This
furnishes a rigid support so that a heavy cut can be taken.

The outside of the casting is next rough-turned with tool _k_, held in
the turret toolpost. This toolpost is then revolved to bring tool _j_
into position, by which the outside is turned true to size, a broad
shaving chip being taken. The toolpost is again swung around, to bring
the cutting-off tool-holder _l_ into position. This holder contains four
blades set the proper distance apart to give rings of the desired width.
Each blade, from right to left, is set a little back of the preceding
one, so that the rings are cut off one after the other, the outer rings
being supported until they are completely severed. After the first four
rings are cut off, the carriage is moved ahead to a second stop, and
four more rings are severed, this operation being continued until the
casting has been entirely cut up into rings.

When the bore of the ring is to be eccentric with the outside, the
holding arrangement shown in the illustration is used. The casting a is
bolted to a sliding chuck-plate _c_, and the outside is rough-turned
with tool _k_ in the toolpost. Finishing tool _j_ is then brought into
action, and the outside diameter is turned accurately to size. Then the
sliding chuck-plate _c_, carrying the work, is moved over a distance
equal to the eccentricity desired, and the work is bored with cutters
_n_ and _n_{1}_ as in the previous case. The turret toolpost is next
revolved and the tools _l_ are used for cutting off the rings. The
reason for finishing the outside first is to secure smooth rings in
cutting off, as this operation should be done when the work is running
concentric with the bore, rather than with the exterior surface.

It will be evident that this method gives a far greater output of rings
than is possible by finishing them in the more primitive way on engine
lathes. The faces of the rings may be finished in a second operation if
desired, or they may be ground, depending on the method used in the
shop where the work is being done, and the accuracy required.

[Illustration: Fig. 17. Turning Gasoline Engine Pistons in Pratt &
Whitney Turret Lathe]

=Piston Turning in Pratt and Whitney Turret Lathe.=--A turret lathe
equipped with tools for turning, facing and grooving automobile g