Industrial Crimp Quality Handbook
Doc No: TM-640160065
Release Date: 00-00-02
UNCONTROLLED COPY
Page 7 of 27
Revision: C
Revision Date: 12-23-09
Within the terminal’s range, an insulation grip may
not completely surround the wire or fully surround
the diameter of the wire. This condition will still
provide an acceptable insulation crimp for most
applications.
A large insulation grip should firmly grip at least
88% of the wire.
A smaller insulation grip should firmly grip at
least 50% of the wire and firmly hold the top of
the wire.
To evaluate the insulation section, cut the wire flush
with the back of the terminal. Once the optimum
setting for the application is determined, it is
important to document the insulation crimp height.
Then, as part of the setup procedure, the operator
can check the insulation crimp height.
Locator
A device for positioning terminals, splices, or
contacts in crimping dies.
MCM (or kcmil)
Unit of area, based on Circular Mil, equal to one
thousand circular mils. Usually used instead of
AWG above wire sizes greater than 4/0 AWG.
Mega (mega, M)
Prefix denoting one million, e.g., one megavolt =
one million volts.
Micro (micro,
)
Prefix denoting one millionth, e.g., one microvolt =
one millionth of a volt.
Mil Spec
Military Specification. A specification used for
qualification of products for acceptability as required
for U.S. Government applications (usually for a
military branch), e.g. Mil-T-7928 covers terminals,
lugs, splices, conductors, crimp style.
Mechanical Strength
To insure how strong the connection is or how much
the wire and terminal must be squeezed to get a gas
tight seal. It’s important to crimp the wires tight
enough to keep them from slipping out of the
connector, but not so tight as to crush the wires in
the terminal, causing them to break off. The
connection is weakened if the wires are cut or
nicked.
Nest
The portion of a crimping die, which supports or
reshapes the barrel during crimping.
PSI, psi
(Pound-Force per Square Inch) Non-SI unit of
pressure. Used mainly to denote pressure of air or
other gas, e.g. 75 psi.
Pound-Force (lbf)
Unit of force, 1lbf is approximately equal to force
exerted on a mass of 1 lb by gravitational force of
Earth at its surface, or a force exerted by that mass
(stationary) on a support (i.e. if mass of 1 lb is
hanged on a wire, it exert a force of ca. 1 lbf
(directed down) on that wire).
Pull Force Testing
Pull force testing is a quick, destructive method to
evaluate the mechanical properties of a crimp
termination.
Pull force testing results out
of allowed range are good
indicators of problems in the
process. Cut or nicked
strands in the stripping
operation, lack of bell mouth
or conductor brush, or
incorrect crimp height or
tooling will reduce pull force.
Wire properties and
stranding, and terminal
design (material thickness
and serration design), also can increase, or
decrease the value of the results of a pull force test.
If results of a pull force tests are within an allowed
range, it assures that proper crimp force has been
applied during crimping. It is crucial as, when
making a crimp, enough force must be applied to
break down the layer of non-conductive oxides that
may build up on the stripped conductor and the tin-
plating on the inside of the terminal grip. This is
necessary to provide a good metal-to-metal contact.
