MIL-M-45424D (MU)
4.4.2 Carburization of ball.-Utilizing samples prepared
as specified in 4.4.1, take three (3) hardness readings 0.05
millimeters apart between 1.14 and 1.65 millimeters from the
edge of the speciment. The average of the three readings must
be at least 75 Knoop points lower than the surface hardness
obtained for the same piece as specified in 4.4.1 to indicate
presence of a core. Failure to meet this requirement shall
cause the specimen to be classed defective.
4.4.3
Susceptibility
to
cracks
under
loading
4.4.3.1 Case assembly.-The case assembly shall be placed
on a flat dry steel surface of 60 micro-inch finish with the
convex curved face facing upward. The sight area shall be
allowed to overhang the side of the steel surface so that the
sides of the case assembly lie flat on the testing surface.
A load of 175 pounds plus or minus 5 pounds shall be applied
with a flat plate, five inches square minimum, centered over
the convex curved face. The load shall be applied and held
for a period of 5 seconds minimum and care shall be taken to
avoid a sudden application of the load with consequent risk
of exceeding the requirement. Observation shall be made for
evidence of cracks, including hairline cracks, as evidence of
noncompliance with 3.3.1.
4.4.3.2 Cover.-The cover shall be placed on a flat dry
steel surface of 60 microinch finish with the concave curved
face facing downward. A load of 60 pounds plus or minus 5
pounds shall be applied with a flat plate, 3-3/4 inches
square centered over the convex curved face. The load shall
be applied and held for a period of 5 seconds minimum and
care shall be taken to avoid a sudden application of the load
with consequent risk of exceeding the requirement. Observation
shall be made to evidence of cracks, including hairline cracks,
as evidence of noncompliance with 3.3.2.
4.4.3.3 Low temperature.-The case assembly and the cover
shall be placed in a cold temperature chamber in such a manner
that no external mechanical stresses are applied. The case
shall be maintained at a temperature of minus sixty-five
degrees Fahrenheit plus or minus 5 degrees for a period of 24
hours, plus or minus 1/2 hour. Observation shall be made for
evidence of cracks, including hairline cracks, as evidence of
noncompliance with 3.3.3.
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