Terminology on topics related to;
nuts and bolts,
threaded fasteners and tightening techniques
MOLYBDENUM DISULPHIDE
A solid lubricant that acts as a high pressure resistant film. Can
be used by itself as a dry lubricant as well as in with other solid
lubricants and in oils and greases. Used in threads, such lubricants
act as a separating film to prevent corrosion formation on the
thread surface (even under adverse temperature and environmental
conditions) ensuring the release of the threaded connection. Such
films can also act as friction stabilisers.
NICKED THREADS
Nicks or indentations in threads can occur during the manufacturing
process and during fastener transportation. In general, nicked
thread problems tend to increase as the thread diameter increases
and for fine pitches.
There are acceptance tests for nicked threads that involve measuring
the maximum torque required to drive a GO gauge down the thread.
Examples of acceptance tests are SAE J123 and the Ford Motor
specification WA990 1993. Nicks and indentations in threads are
sometimes referred to as gouges.
NOMINAL DIAMETER
The diameter equal to the external diameter of
the threads.
NUT DILATION
Under load, the wedging action of the threads causes dilation of the
nut resulting in an increase in the minor diameter of the nut, and
reducing the effective shear areas of both the external and internal
threads. |
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