to provide the desired wearing qualities. At the same
time, the piston pin must not be brittle. To satisfy the
overall requirements of a piston pin, it was found that
a casehardened steel pin is best. Casehardening is a
process that hardens the surface of the steel to any
desired depth. The pin is also made hollow to reduce the
overall weight of the reciprocating mass.
c. Configurations. The following are the
(2) A semifloating pin (B, fig. 3-32) is locked to the
Figure 3-26. Top Ring Groove Insert.
connecting rod by a screw or friction. The pin pivots
freely in the piston pin bosses.
3-7. Piston Pins.
(3) The full-floating piston pins (C, fig. 3-32) pivot freely
a. General (Fig. 3-30). The piston pin serves to
in the connecting rod and the piston pin bosses. The
connect the piston to the connecting rod. It passes
outer ends of the piston pins are fitted with lockrings to
through the pin bosses in the piston and the upper end of
keep the pin from sliding out and contacting the cylinder
the connecting rod.
b. Construction (Fig. 3-31). A piston pin must be hard
Figure 3-27. Oil Control Rings