MIL-DTL-24643C
4.8.17.3 Procedure. Each specimen shall be wiped with a clean, dry cloth to remove any lubricant or dirt. One
specimen shall then be selected and mounted between the two fixed supports of the abrading machine. Mounting
shall be accomplished such that the specimen shall be as taut as practicable, and such that the braided cotton tape
shall repeatedly abrade the same portion of the specimen printed identification at all times during the test. The
automatic counter shall be set initially to zero. The abrading machine motor shall then be turned on. The braided
cotton tape shall be allowed to reciprocate and abrade the specimen printed identification either until the printed
identification is no longer legible in its abraded region, or until not fewer than the specified number of abrasive
cycles (see 3.1) have been completed, whichever occurs first. The number of abrasive cycles completed shall then
be noted, and the remaining specimens then tested in an identical manner.
4.8.17.4 Observation. Specimen failure shall be construed if the median value of the number of abrasive cycles
completed on each specimen is less than that specified (see 3.1).
4.8.18 Permanence of printing (jacket). This test shall determine the ability of printed information of jacketing
material to remain legible in the presence of repeated abrasion.
4.8.18.1 Specimen. The specimen shall consist of a piece of completed cable which shall have sufficient length
for use in the test as specified in 4.8.18.3.
4.8.18.2 Special apparatus. Apparatus shall include an abrading machine which shall support and secure the
specimen such that it is straight and horizontal, and which shall abrade the specimen printed identification by means
of a motor driven transversely reciprocating steel pin. The steel pin shall have a diameter of 0.025±0.001 inch
where it abrades the specimen, and shall have a surface roughness of not less than 2 micro inches, as specified in
ANSI B46.1. (A selected sewing needle may satisfy these requirements). One possible arrangement for the
abrading machine is shown on figure 2. The steel pin shall be horizontal and perpendicular to the specimen axis,
shall ride along the top of the specimen and shall be weighted to bear down on the specimen with a force of 1+1/16, - 0
pound at all times during the test. The pin shall be reciprocated at a rate of 60±2 cycles per minute such that the pin
is drawn along the specimen for a distance of +1/16, - 0 inches in each direction (¾ inch minimum total excursion)
during each cycle. The abrading machine shall incorporate in automatic counter to total the number of times that the
specimen is abraded by the steel pin during the test.
4.8.18.3 Procedure. The specimen shall be wiped with a clean, dry cloth to remove any lubricant or dirt, and
shall be secured in the abrading machine with the specimen printed identification facing upwards, where it is to be
abraded by the steel pin. The automatic counter shall be set initially to 0. The abrading machine motor shall be then
turned on, allowing the steel pin to reciprocate and abrade the specimen printed identification either until printed
identification is no longer legible in the abraded region, or until not fewer than 125 abrasive cycles have been
completed, whichever occurs first. The number of abrasive cycles completed shall then be noted. This test shall
next be repeated 4 more times (5 times total), subjecting a fresh portion of the specimen printed identification to
abrasion each time.
4.8.18.4 Observation. Specimen failure shall be construed if the median value of the number of abrasive cycles
completed during each of the 5 tests is less than 125.
4.8.19 Physical tests (aged) on insulation and jacket. This test shall determine whether or not various
insulating and jacketing materials have been properly processed, by means of tension measurements. This test
makes provision for making tension measurements both before and after these materials have been artificially aged.
4.8.19.1 Specimens. Each specimen shall consist of a single piece of insulation or jacketing, which shall have
sufficient length for use in the test as specified in 4.8.30, as specified (see 3.1). Specimens shall be removed from
completed cable.
4.8.19.2 Special apparatus. Apparatus shall consist of a forced fresh air circulating oven for supporting the
requirements as specified in 4.8.19.3.a. The oven air temperature shall be measured in the immediate vicinity of the
specimens.
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