and the machine is ready to turn two of the
pins. After these have been machined, the fixtures are again aligned by
the locking pins, the two T-bolts of the headstock fixture and the
hinged clamp at the tailstock are released, the indexing plunger is
withdrawn and the headstock fixture and crank are turned 180 degrees or
until the index plunger drops into place. The crank is then clamped at
the tailstock end and the revolving fixture is secured by the two
T-bolts previously referred to. After the locking pins are withdrawn,
the lathe is ready to turn the two opposite pins.

[Illustration: Fig. 27. Diagrams showing Arrangements of Tools on
LeBlond Lathe]

=Operation of Special Crankshaft Lathe.=--The total equipment of this
machine (see Fig. 27) is carried on a three-tool turret tool-block. The
method of turning a crankshaft is as follows: A round-nosed turning tool
is first fed into a cross stop as illustrated in the plan view at _A_,
which gives the proper diameter. The feed is then engaged and the tool
feeds across the pin until the automatic stop lever engages the first
stop, which throws out the feed automatically. The carriage is then
moved against a positive stop by means of the handwheel. The roller
back-rest is next adjusted against the work by the cross-feed handwheel
operating through a telescopic screw, and the filleting tools are
brought into position as at _B_. These are run in against a stop,
removing the part left by the turning tool and giving the pin the proper
width and fillets of the correct radius. If the crankshaft has straight
webs which must be finished, two tools seen at _b_ are used for facing
the webs to the correct width. During these last two operations, the
crank is supported by the roller back-rest, thus eliminating any
tendency of the work to spring.

[Illustration: Fig. 28. (A) Spherical Turning with Compound Rest. (B)
Concave Turning]

After one pin is finished in the manner described, the back-rest is
moved out of the way, the automatic stop lever raised, the carriage
shifted to the next pin, and the operation repeated. The tools are held
in position on the turret by studs, and they can be moved and other
tools quickly substituted for pins of different widths. This machine is
used for rough-turning the pins close to the required size, the
finishing operation being done in a grinder. It should be mentioned, in
passing, that many crankshafts, especially the lighter designs used in
ag