MIL-DTL-8777F
3.3.3 Insulating materials.
3.3.3.1 Primary insulation. The primary insulation shall be of silicone rubber, applied by extrusion or
taping. If a silicone rubber tape is used, it shall be fused into a homogeneous mass.
3.3.3.2 Inner braid. The inner braid shall consist of glass fibers or a combination of glass fibers and
polyester fibers covering the primary insulation. The inner braid shall be treated with a heat-resistant
finisher.
3.3.3.3 Outer jacket. The outer jacket shall be as specified in the applicable MS sheet.
3.4 Design and construction.
3.4.1 Conductors.
3.4.1.1 Conductor coating. Individual strands shall be uniformly coated with a smooth continuous layer
of commercially pure silver having a minimum thickness of 40 micro inches when tested as specified in
4.6.2.2. Following the continuity of coating test in 4.6.2.1, there shall be no evidence of exposed copper.
3.4.1.2 Stranding.
3.4.1.2.1 Concentric-lay. Wire sizes 22 through 12 shall be constructed with concentric-lay conductors
and as specified in table I. Concentric-lay shall be interpreted to be a central core surrounded by one or
more layers of helically wound strands. It is optional for the direction of lay for successive layers to be
alternately reversed (true concentric-lay) or to be in the same direction (unidirectional lay). When
unidirectional lay is used, the strands shall be assembled in a geometric arrangement of concentric layers,
so as to produce a smooth and uniform conductor, circular in cross-section and free of any crossovers,
high strands or other irregularities. The direction of lay of individual strands in the outer layer of the
concentrically stranded conductors of finished wire shall be left hand. The length of lay in the outer layer
shall be not less than 8 nor more than 16 times the maximum conductor diameter specified in the
applicable MS sheet.
3.4.1.2.2 Rope lay. Wire sizes 10 through 00 shall be rope lay and as specified in table I and as
follows:
a. Rope lay stranded conductors shall be laid up concentrically with a center core surrounded by one
of more helically wound members. It is optional for the direction of lay for successive layers to be
alternately reversed (true concentric-lay) or to be in the same direction (unidirectional lay). The
length of lay of the outer layer of rope lay stranded members forming the conductor shall be not
less than 10 nor more than 14 times the outside diameter of the completed conductor. The
direction of lay of the outside layer may be either left or right hand.
b. Members of rope lay stranded conductors: The length of lay of the conductors composing the
stranded members shall be not greater than 16 times the outside diameter of the member.
Stranding of the individual members may be concentric or bunch.
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