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Catalog
AIRCRAFT HARDWARE
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TORQUING Except as a last resort, do not torque a bolt by turning it. Tighten or torque castellated nuts as
you would any other standard nut. If the slots and cotter pin hole in the bolt will not line up for safetying,
tighten the nut to the next slot even though the recommended torque values will be exceeded. This over
torquing leeway applies only to castle nuts and not others. Cotter pins when used should fit snugly but not so
tight you have to hammer them into the bolt hole. Bend the ends so that one end is over the end
of the bolt reaching to its center or slightly beyond. The other leg is bent snugly against the nut. Coarse
threads require slightly less torque and so do shear nuts. Actually, about 1/2 the amount of torque is sufficient for
them. And, finally, even if you don't use a torque wrench - no self-respecting homebuilder will ever allow
himself be caught using a pair of pliers to tighten a nut. BOLTING PRACTICES One of the most
common methods of securely joining two objects together is the use of a bolt-nut combination. This provides a
unit which has a predictable strength, unless the bolt has been improperly installed. If this happens, strength
is substantially reduced and failure may result. Aircraft bolts are about .001 to .003 inch smaller than
their nominal diameter, permitting easy installation in a properly drilled hole. The hole should be drilled such
that the head of the bolt will lie solidly against the surface of the metal, as seen in the figure. Burrs around
the edge of the hole should be removed before the bolt is inserted. Bolts are generally used in some
shear application, therefore the smooth shank should extend entirely through the hole. No threads should be
in contact with the bearing surface, as seen in the figure. Most applications using bolts require the use of
a washer. The proper washer for the job must be carefully chosen. The bolt installation is complete when the unit
has been torqued to the specification set down by the manufacturer. |
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