MIL-DTL-8777F
4.6.4.14.2 Wire weight procedure II. The net weight of the finished wire on each reel or spool shall
be obtained by subtracting the tare weight of the reel or spool from the gross weight of the reel or spool
containing the finished wire. The net weight of wire on each reel or spool shall be divided by the
accurately determined length of finished wire on that reel or spool and the resultant transposed to pounds
per 1,000 feet. When wood or other moisture absorbent materials are used for reel or spool construction,
weight determinations shall be made under substantially the same conditions of relative humidity.
4.6.4.15 Thermal shock resistance.
4.6.4.15.1 Preparation of specimen. A specimen of wire, 5 feet long, shall be prepared by carefully
removing 1 inch (25.40 mm) of insulation from each end of the wire. (For purposes of this test, insulation
is defined as all layers of no conducting material covering the electrical conductor, e.g., primary
insulation, all tapes and braids, and the jacket.) A razor blade or equivalent, held perpendicular to the
axis of the wire, shall be used to cut the insulation for the removal operation. The length of exposed
conductor at each end of the specimen shall be measured to the nearest 0.01 inch (.25 mm). The
specimen shall be formed into a loose coil not less than 1 foot in diameter and shall be laid on a wire
screen for handling throughout the test.
4.6.4.15.2 Test procedure. The specimen shall be placed for 30 minutes in a preheated air-circulating
oven at the temperature specified in the applicable MS sheet, or at the rated temperature of the wire if no
oven temperature for the test is specified in the applicable MS sheet. It shall then be removed from the
oven and, within 2 minutes, placed in a chamber which has been precooled to -55° ±2°C. The specimen
shall be exposed to this temperature for 30 minutes, after which it shall be removed and allowed a
minimum of 30 minutes to return to room temperature, 20° to 25°C. At the conclusion of this cycle, the
distance from the end of each layer of insulation to the end of the conductor shall be measured to the
nearest 0.01 inch (.25 mm). This thermal shock cycle and the measurements shall be repeated for an
additional three cycles (a total of four cycles). Any measurement varying form the original measurement
by more than the amount specified in the applicable MS sheet, or by more than 0.06 inch (1.52 mm), if no
amount is specified, shall constitute failure. Any flaring of any layer shall also constitute failure.
4.6.4.16 Durability of color markings. The durability of product identification or color strippings applied
to the wire for coding shall be evaluated at 20° to 25°C as follows:
4.6.4.16.1 Durability testing apparatus. The markings durability tester shall be designed to hold a short
specimen of finished wire firmly clamped in a horizontal position with the upper longitudinal surface of the
specimen fully exposed. The instrument shall be capable of rubbing a small cylindrical steel mandrel
(usually a needle), 0.025 inch (.64 mm) in diameter, repeatedly over the upper surface of the wire, in such
position that the longitudinal axes of the mandrel and the specimen are at right angles to each other with
cylindrical surfaces in contact. A weight affixed to a jig above the rubbing mandrel shall control the thrust
exerted normal to the surface of the insulation. A motor driven, reciprocating cam mechanism and
counter shall be used to deliver an accurate number of abrading strokes in a direction parallel to the axis
of the specimen. The length of the stroke shall be 0.375 inch (9.53 mm) and the frequency of the stroke
shall be 120 strokes (60 stroking cycles) per minute.
4.6.4.16.2 Durability testing procedure. In performing the test, a specimen of wire shall be mounted in
the specimen clamp and the applicable total weight shall be applied through the rubbing mandrel to the
marked surface. The counter shall be set at zero and the drive motor started. The specimen shall be
observed throughout the progress of the test and, as soon as a continuous line of the printed marking is
removed under the mandrel, the number of cycles shall be recorded. Three specimens from each sample
unit shall be tested and the results from the three specimens shall be averaged.
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