Yanmar 1GM User Manual page 14

GENERAL INFORMATION
7
Common nut
Plain
Internal tooth
Self-locking nut
Wing nut
Folding
External tooth
Correct
installation
of cotter pin
Flat washers are often used between a lockwasher and a
fastener to provide a smooth bearing surface. This allows
the fastener to be turned easily with a tool.
NOTE
As much care should be given to the selec-
tion and purchase of washers as that given
to bolts, nuts and other fasteners. Avoid
washers that are made ofthin, weak materi-
als. These will deform and crush the first
time they are torqued, allowing the nut or
bolt to loosen.
Cotter Pins
Washers
There are two basic types of washers: flat washers and
lockwashers. Flat washers are simple discs with a hole to
fit a screw or bolt. Lockwashers are designed to prevent a
fastener from working loose due to vibration, expansion
and contraction. Figure 12 shows several types of wash-
ers. Washers are also used in the following functions:
a. As spacers.
b. To prevent galling or damage of the equipment by
the fastener.
c. To help distribute fastener load during torquing.
d. As seals.
•
Cotter pins (Figure 13) are used to secure fasteners in a
special location. The threaded stud or bolt must have a
hole in it. The nut or nut lock piece will have castellations
around its upper edge into which the cotter pin fits to keep
it from loosening. When properly installed, a cotter pin is
a positive locking device.
Purchase a cotter pin that will fit snugly when inserted
through the nut and the mating thread part. The cotter pin
should not be so tight that it has to be driven in and out, but
it should not be so loose that it can move or float after it is
installed.
Before installing a cotter pin, tighten the nut to the rec-
ommended torque specification. Ifthe castellations in the
nut do not line up with the hole in the bolt or stud, tighten
the nut until alignment is achieved. Do not loosen the nut