MIL-DTL-17901C(SH)
4.4.2 Selection of sample bearings and preparation of test specimens for qualification testing - stave shaped
bearings only (class III). The bearings used for qualification shall be between sizes 4 through 10 with a length of 36
inches or longer, except for performance test bearings that are size 1. The selection of sample stave bearings for
visual, dimensional, and hardness tests and the preparation of test specimens shall include the following:
a. Samples for visual, dimensional, and hardness tests. From a production run of 40 or more staves,
select a random sample in accordance with 4.4.1. The visual, dimensional, and hardness tests shall be performed on
these selected staves in the as manufactured condition (prior to cutting stave specimens) in accordance with 4.5.1,
4.5.2 and 4.6.1, respectively. Unless otherwise specified (see 6.2), any bearing/stave in the sample containing one or
more visual, dimensional, or hardness defect shall be rejected and 100% inspection of all bearings/staves for that
particular test is mandated.
b. Samples and specimens for tensile strength and elongation tests. The rubber specimens for tensile and
elongation testing shall be obtained from the facing material of three sample staves. Select three sample staves from
those selected in 4.4.2.a and cut into 6-inch (+0.5, -0 inches) lengths, marking each piece taken from the first stave
with the number 1, each piece taken from the second stave with the number 2, and each piece taken from the third
stave with the number 3. Select one 6-inch (+0.5, -0 inches) stave section from each stave and identify on the rubber
for use in the before aging test. Select a second set, one from each stave, and identify them on the rubber for use in
the after aging test. The rubber for the tension and elongation test shall be sliced from the surface of each of these
staves by means of a fine toothed band saw and buffed to a thickness of not less than 0.060 inch or more than 0.120
inch in accordance with ASTM D412. Use the backing material for testing in accordance with 3.2.3. The remaining
6-inch pieces shall be used in subsequent tests.
c. Samples and specimens for delamination tests. The rubber specimens for delamination testing shall be
obtained from the 6-inch (+0.5, -0 inches) stave lengths cut as in b above. Select three stave pieces, one from each
stave, and remove the rubber from the backing at the interface bond. Cut specimens 3 inches by 1 inch (+/-1/16 inch)
by the thickness of the rubber facing from the three separate staves pieces.
d. Samples and specimens volume change tests. The rubber specimens for the volume change testing
shall be obtained from the 6-inch (+0.5, -0 inches) stave lengths cut as in b above. Select one 6-inch stave section
from each of the three staves and identify on the rubber for use in the water immersion test. Select a second set of
three from each of the staves and identify on the rubber for use in the oil immersion test. Cut one specimen, 2
inches by 1 inch (+/-1/16 inch) with a thickness not to exceed 1/16 inch, from the surface of each of the six samples
above. These samples are now ready for aging by oil and water immersion.
e. Samples and specimens for adhesion bond tests. For class III staves, obtain one stave from each slab
from which adhesion test specimens may be cut. The rubber facing of these staves shall be buffed to a uniform
thickness of ¼ inch (+/-1/16 inch) (see ASTM D3183 for buffing procedures). Cut each stave into three 6-inch (-0.0
inches) lengths, marking the first stave specimen with the number 4, the second stave specimen with the number 5,
the third stave specimen with the number 6, then the first stave specimen from the second stave with the number 7,
etc. The test specimens required for each type of test shall be from different staves. The stave side angle profile of
the test specimens shall not be removed or modified. The test specimens for adhesion pull testing shall have the
rubber facing divided into three longitudinal strips by means of saw cuts perpendicular to the rubber face. The cuts
shall go completely through the rubber and to a depth of approximately 1/16 inch into the backing. A cut shall be
made ½ inch (+/-1/32 inch) from each longitudinal edge of stave facing. Also, two longitudinal cuts equally spaced
about the centerline a distance of ½ inch (+/-1/32 inch) apart measured along the bond interface shall be made. The
rubber facing between the center and edge strips should be removed from the backing at the bond. This leaves a ½-
inch center strip and two ½-inch wide edge strips. For adhesion testing, these three strips will be pull tested
individually. (See Figure 1 for a cross section view of a test specimen.) The test specimens are now ready for the
type of aging required by the particular tests (see 4.6.5).
4.4.3 Selection of sample bearings and preparation of test specimens for qualification testing - cylindrical
shaped bearings (class II, IV, and V only). The cylindrical bearings used for qualification tests shall have an inside
diameter (I.D.) of 6 inches or greater and shall be 18 inches or greater in length. The selection of sample cylindrical
bearings for visual, dimensional, and hardness inspection and the preparation of test specimens shall include the
following:
a. Samples for visual, dimensional and hardness tests. From a production run of 8 to 15 bearings for
class II and IV, and a production run of 1 or more for class V, select a random sample in accordance with 4.4.1. The
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