MIL-DTL-5521C
4.5.2.2 Tests. Quality control tests of material shall consist of the following tests, as described under 4.6.
a. Tensile strength (see 4.6.4)
b. Elongation (see 4.6.5)
c. Grease (see 4.6.6)
d. Chlorides (see 4.6.7)
e. Sulfates (see 4.6.8)
f. Ash (see 4.6.9)
g. Chromic oxide (see 4.6.10)
4.5.3 Rejection and retests.
4.5.3.1 Individual washers. If any hydraulic packing back-up washer fails to comply with any of the
requirements of 4.5.1, it shall be rejected.
4.5.3.2 Material specimens. Failure of any sample to comply with any one of the requirements of this
specification shall require a retest of the lot from which the sample was selected. The number of special
backs and special butt bends to be sampled for retest shall be twice the number listed in 4.5.2.1. If any of
the retest samples fail to comply with any of the requirements set fourth herein, the lot of material from
which the samples were selected shall be rejected. A lot of material is defined as any number of special
backs and special butt bends delivered from the tannery to the fabricator as a single shipment.
4.6 Test methods.
4.6.1 Examination of product.
4.6.1.1 Each individual washer shall be carefully examined to determine compliance to the applicable
standards for acceptable workmanship, finish, and trim.
4.6.1.2 Washers shall be inspected for outside diameter, inside diameter, width, thickness, and cross
sectional corner angles where applicable. All dimensions shall conform to the applicable standard.
Dimensional inspections shall be preformed on a sample basis in accordance with ASQ Z1.4, using a
single sample plan, general inspection level I, with a AQL of 1.0 percent defective.
4.6.2 Thickness. Leather shall be selected for thickness with a minimum of splitting or skiving. In no
case shall leather .063 inch (1.59 mm) thick be obtained by splitting leather which was originally .125 inch
(3.18 mm) thick.
4.6.3 Cracking resistance. The cracking resistance test shall be in accordance with Method 4011 of
FED-STD-311. The diameter of the mandrel shall be .5 inch (12.7 mm). The test specimen in
accordance with 4.5.2.1.1 shall be initially heated to 71°C (160°F) and maintained at that temperature at
all times throughout the test. The test specimen shall remain in the clamped, bent position at 71°C for
seven days, and it shall not crack open on the grain side in the area around the bend.
4.6.4 Tensile strength. The tensile strength test shall be in accordance with Method 2021 of FED-STD-
311. Four test specimens in accordance with 4.5.2.1.1 shall be cut from the sample for this test. The
tensile strength for any one test specimen shall be a minimum of 2500 psi (17.24 Mpa) with an average of
not less than 3000 psi (20.68 Mpa) before splitting. The tensile strength for each of the four test
specimens shall be recorded in addition to the average value.
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