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Terminology on topics related to;
nuts and bolts,
threaded fasteners and tightening techniques COEFFICIENT OF
FRICTION
A dimensionless number representing the ratio of the friction force
to normal force. Typically for threaded connections it is between
0.10 to 0,18 but can vary significantly depending upon the materials
used and whether a lubricant has been used.
COMMINGLING
A term used to describe the undesirable practice of mixing fasteners
from different batches that are the same size and grade in the same
container.
CONE PROOF LOAD
This is an axial applied force applied to a nut when it is seated on
a cone shaped washer which has an included angle of 120 degrees.
Failure in this test is usually due to the nut splitting.
The
intention of the test is to introduce a nut dilation operation which
will assess the potential detrimental effects of surface
discontinuities. This type of test is sometimes applied to nuts
which are intended for high temperature service. YIELD CONTROLLED TIGHTENING
A fastener tightening method which allows a fastener to be tightened
to yield. The angle of rotation of the fastener is measured relative
to the applied torque, yield being assessed when the slope of the
relationship changes to below a certain value. Sometimes called
joint controlled tightening.
ZINC ELECTROPLATING
Zinc electroplating is a common way to protect threaded fasteners
from the effects of corrosion. Zinc electroplating can be completed
in acid chloride, alkaline or cyanide baths. Supplemental coatings
are frequently applied to zinc electroplating. These coatings, such
as zinc phosphate or chromate conversion, provide a protective
passivation layer on the zinc which assists in reducing the
corrosion rate. |
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