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Important Facts
About Crimping
Time Line for Crimp MS3191-4 also introduced the use of Specifications state the requirements
Technology the double tipped indenter to produce in terms of millivolt drop at a designated
an eight indent crimp pattern which has current.
1940s All terminations were soldered consistently achieved superior tensile pull
(Hard-wired) off values. The mechanical strength of a crimped
joint and hence its pull-out force (tensile
1953 AMP introduced Crimp MS3191-4 introduced the concept of strength), varies with the deformation
Barrel Terminals a turret head containing three locators applied. Therefore, by properly shaping
which could be used without separating the deformation a high pull-out force can
1957 Cannon Brothers experimented any of them from the basic crimp tool. be achieved, i.e. the crimp die of the tool
with Machined Contacts with determines the crimp configuration and
Crimp Barrels In 1969 two military specifications for deformation.
crimp tools were developed to replace
1960 Buchanan introduced the the existing military drawings. They were The dies in the tool determine the
4 Indent Crimp Tool with a MIL-T-22520C (Navy) and MIL-T-83724 completed crimp configuration which
Ratchet (Ref: MS3191) (USAF) which defined a standard size is generally an element of contact and/
crimp tool similar to the MS3191-4, but or connector design. Some of the design
1963 MS3191-1 was published as the with an expanded eight step crimp depth considerations are: a) The type of contact,
first Crimp Tool Standard. range. These specifications also defined a its size, shape, material and function,
miniature crimp tool to crimp conductors b) The type and size of wires to be
1965 MS3191-4 introduced by as small as AWG 32. accommodated, c) The type of tooling
Daniels Manufacturing Corp. into which the configuration must be built.
Both documents were combined in
1969 MIL-T-22520 published 1971 into MIL-C-22520D. All previous Eight Indent
and dated to replace all military standards for crimp tools were
previous specifications then cancelled including the MS3191. Four Indent
This list includes specifications for indent
1974 Changed to MIL-C-22520, crimp tools, terminal lug crimp tools, Two Indent
and many Slash Sheets added pneumatic tools, coaxial cable crimp tools
and connector service kits. Hexagonal Crimp
1996 Changed to MIL-DTL-22520
2010 Changed to AS22520 MIL-DTL-22520 established a single Circular Crimp
specification which set forth performance
CRIMPING: THEN AND NOW requirements for all crimp tools to be used B Crimp
on military standard electrical connectors.
The first multi-pin connectors were This eliminated the waste and confusion Nest & Indent Crimp
terminated by soldering the conductor to which accompanied the overlapping appli-
non-removable contacts. However, high cations of many different “standard” crimp Captive Crimp
temperature applications and the need for tools called out by a deluge of unrelated
simple and reliable field service led to the military drawings. Insulation Displacement
introduction of connectors with removable
contacts. These were crimped onto the THE CRIMPING CONCEPT PAGE 1
conductor rather than being soldered.
Crimping is a method of firmly
The first standard crimp tool developed attaching a terminal or contact end to an
to crimp these new contacts was intro- electrical conductor by pressure forming
duced in the early sixties. MS3191-1, or reshaping a metal barrel together
a military drawing, defined this tool and with the conductor. The forming of a
its accessories. The MS3191-1 utilized satisfactory crimp depends on the correct
a four indent crimp pattern together with combination of conductor, crimp barrel
a positive stop locator which controlled and tool.
the travel of the indenters (crimp depth).
When applied with a properly matched
The MS3191-1 design was a compro- tool, a union is established which has
mise between simplicity of operation and both good electrical and mechanical
crimp performance since the crimp depth characteristics. The tool will provide these
for any given contact was not adjustable requirements consistently and reliably
to accommodate the differing diameters with repeatability assured by quality cycle
of the conductors to which it would be controlled tooling. There are several
crimped. It was, however, suitable for the common configurations of crimped joint;
crimp connectors of that era. several examples are shown below.
An improved tool design featuring The electrical resistance of a properly
independently adjustable crimp depths designed and controlled crimped joint
was soon introduced as MS3191-4. The should be equal to, or less than, the
MS3191-4 had an internal adjustment, resistance of an equal section of wire.
totally independent of the locator, which
permitted the selection of seven separate www.itmash.ru
crimp depths, allowing optimal crimping
of conductors ranging from AWG 12 to dmc@itmash.ru
26 regardless of the wire barrel size of
the contact. +7 (495) 668-13-58
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