Broadly
defined, a self-clinching fastener is any device, usually threaded,
that, when pressed into ductile metal, displaces the host material
around the mounting hole, causing it to cold flow into a specially
designed annular recess in the shank or pilot of the fastener.
A serrated clinching ring, knurl, ribs or hex head prevents the
fastener from rotating in the host material once it has been properly
inserted. Thus, self-clinching fasteners become a permanent part
of the panel, chassis, bracket, or other item into which they
are installed.
Generally,
self-clinching fasteners take less space and require fewer assembly
operations than caged or anchor nuts. They also have greater reusability
and more holding power than sheet metal screws. They are used
chiefly where good pullout and torque loads are required in sheet
metal that is too thin to provide secure fastening by any other
method. Even if the sheet is thick enough to sustain tapping,
it may actually be more economical to use self-clinching fasteners
with gaugeable threads. They can be installed during fabrication
or during final assembly to eliminate loose hardware. In fact,
the use of self-clinching fasteners often will support a thinner
sheet metal, and permit a real reduction in installed cost over
the cost of other fastener designs. Because of their compact design
and low profile, they provide for a neat appearance, too.
As
a rule, a self-clinching fastener should be specified whenever
a component must be readily replaced and where "loose" nuts and
hardware wouldn't be accessible. If the attaching "nuts" and "screws"
can't be reached after a chassis or cabinet is assembled, self-clinching
fasteners can be installed during metal fabrication and can simplify
and expedite component mounting and assembly operations, including
those performed in the field. |
