MIL-DTL-24640C
4.4.5 Group B examination and tests. Group B examination and tests as required by the specification sheet
shall be performed on specimens taken from samples selected in accordance with 4.4.3.2.
4.4.6 Group C examination and tests. Group C examination and tests as required by the specification sheet
shall be performed on specimens taken from samples selected in accordance with 4.4.3.3.
4.4.7 Group D examination and tests. Group D examination and tests as required by the specification sheet,
shall be performed on specimens taken from samples selected in accordance with 4.4.3.4.
4.5 Test conditions. Unless otherwise specified (see 3.1), the examination and tests specified in tables XI and
XIII shall be made at standard ambient conditions as follows:
Temperature: 23±2.0 °C
a.
Humidity: 50±40 percent RH
b.
4.6 Visual and dimensional examination. Cables shall be visually examined to verify that the materials, design,
construction, physical dimensions, marking, and workmanship are as specified in 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, and 3.7.
Concentricity, wall thickness and dimensional examinations shall be made as follows:
4.6.1 Concentricity and wall thickness. The concentricity of the finished wire and the finished cable jacket
shall be determined in accordance with 4.6.1.1, as applicable. Wall thickness measurements shall be made on cross
sections of the finished wire or cable jacket under suitable magnification. The wall thickness shall be the shortest
distance between the outer rim of the finished wire insulation or cable jacket and the outer rim of the underlying
conductor or shield strand.
4.6.1.1 Component wire and cable jacket. The concentricity of the finished wire and cable jacket shall be
determined by first locating and recording the minimum wall thickness measured on a cross section of the finished
wire and cable jacket. From this point on the outer rim of the finished wire and cable jacket (at which the minimum
wall thickness was measured), three more reference points (90 degrees apart) on the outside rim of the finished wire
and cable jacket shall be established. At each of these three reference points, the nearest member of the conductor
shall be selected, and the minimum wall thickness be measured. The average of the four readings shall be the
average wall thickness. The percent concentricity shall be defined 100 times the ratio of the minimum wall
thickness to the average wall thickness.
4.6.2 Dimensions. Measurements shall be made on not less than a 12-inch length of cable taken from the end
of the sample unit. Inner components shall be made accessible by stripping and removing the outer components so
as not to nick, cut, cold work, or otherwise damage the component to be measured. Four points for measurement
shall be located 3 to 4 inches apart along the finished wire specimen or finished cable specimen lengths, as
applicable. Measurements shall be made at each point at two perpendicular planes or as required to assure the
minimum and maximum reading is attained at each point. A total of eight measurements shall be performed on each
specimen. The minimum, maximum, and average value shall be recorded, as applicable. Measurements shall be
made with a micrometer, caliper, or equal. A PI-tape may be used for measurements of diameters greater than 0.250
inch.
4.7 Test methods (physical).
4.7.1 Abrasion resistance. Abrasion resistance of cable jacket material shall be determined as specified in
4.7.1.1 Specimens. One cable jacket test specimen shall be prepared by extruding material onto a 16 AWG
(19/29) conductor. The material shall be manufactured using process conditions as close as possible to those used to
produce the overall cable jacket and shall have an overall cable diameter of 0.119+0.001, -0.000 inch.
4.7.1.2 Special apparatus. Apparatus shall include the following:
a. Abrading machine A cylinder, which incorporates 2 abrading elements on its surface, which is motor
driven to rotate about a horizontal axis at 17+3, -2 revolutions per minute (rpm) and over which the specimen is
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