Figure 3-28.Full- and partial-skirted pistons.
The piston pin (fig. 3-29) serves to connect the
piston to the connecting rod. It passes through the pin
bosses in the piston and the upper end of the connecting
rod. The piston pin must be hard to provide the desired
wearing qualities. At the same time, the piston pin must
not be too brittle. A case-hardened steel pin is the best to
satisfy the overall requirements of a piston pin. Case
hardening is a process that hardens the surface of the
steel to any desired depth. The pin is also hollow to
reduce the overall weight of the reciprocating mass.
They are lubricated by splash from the crankcase or by
pressure through passages bored in the connecting rod.
There are three methods used for fastening a piston
to the connecting rod. The following are the three
Figure 3-29.Piston pin.
different types of piston pins (fig. 3-30):
Figure 3-30.Types of piston pins.