MIL-DTL-17901C(SH)
accelerated aging of the specimens is not required. The stave side angle profile of the test specimens shall not be
removed or modified.
4.4.5 Selection of samples for conformance inspection - cylindrical bearings only (class II and IV). Sample
cylindrical bearings shall be selected from each lot in accordance with Table VI. The conformance inspection shall
be performed on these bearings in the as-manufactured condition. Conformance inspection of cylindrical bearing,
class II, does not require adhesion pull testing due to superior bonding record. Therefore, there is no need to cut any
of the bearings into test specimens.
a. For class IV bearing, select three bearings for adhesion pull testing, cut the bearings along each water
groove to create the test specimens. Buff facings of each specimen to ¼-inch (+/-1/16-inch) thickness (see ASTM
D3183 for buffing procedure). They shall each have two longitudinal cuts in the facing, equally spaced about the
centerline, ½ (+/-1/32) inch apart. The cuts shall go completely into through the rubber facing to a depth of
approximately 1/16 inch into the backing. The rubber on each side of the center strip shall be removed from the
backing at the bond. This leaves one ½-inch center strip per test specimen. The test specimens are now ready for
adhesion bond test in accordance with 4.6.5, except accelerated aging of the specimens is not required.
b. A visual, dimensional, and hardness inspection shall be performed on each bearing of the statistical
sample in accordance with 4.5.1, 4.5.2, and 4.6.1, respectively. This completes the conformance requirements for
class II and IV bearings. 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.
4.4.6 Selection of samples and preparation of test specimens for conformance inspection partial-arc bearings
(class V) only. Selection of samples and preparation of the test specimens for conformance inspection (class V)
shall be as follows:
a. A visual, dimensional, and hardness inspection shall be performed on each part (in the as-
manufactured condition) in accordance with 4.5.1, 4.5.2, and 4.6.1, respectively. This portion of the conformance
inspection shall be successfully passed before proceeding with the preparation of test specimens for adhesion bond
testing. In cases of rejection, the manufacturer shall isolate the cause of the defects and produce another part for
inspection in which the cause of the previous defect is eliminated.
b. Specimens for adhesive bond testing. Test specimens shall be taken from prolongations removed from
the as-manufactured bearing. At least test strips are required for each bearing. The use of a single specimen with
three individual test strips may be used or three specimens each with one test strip may be used. The strips shall be
machine cut to provide one test strip ½ inch wide by a minimum of 6 inches long. For specimens with three test
strips, a space of ¼ inch minimum shall be provided between each strip to prevent inadvertent damage to the
adjacent bond during testing resulting in a loss in recorded pull force. The general test strip configuration shall be as
represented by Figure 3 except that the test strip will have a radius equal to that of the prolongation from which it is
taken, the specimen shall be machined or cut down to the adhesive so that only the ½ inch wide rubber strip is
subjected to the adhesive bond pull test. No aging of specimen is required.
c. Specimens for flexural modulus testing. Preparation of specimens shall be in accordance with ASTM
D790 per Table II of this specification, except as follows. Test specimens shall be taken from prolongations cut
from the production material. The specimens may be curved in lieu of flat, having the same radius as the production
material. The length of the test specimen (i.e., span-to-depth ratio) shall be as recommended by ASTM D790.
However, if prolongations of sufficient length to provide the recommended span-to-depth ratio cannot be obtained
from the production material due to tooling limitations (e.g., insufficient mandrel length), then shorter specimens
may be tested. In no case shall the span-to-depth ratio of test specimens be less than 8 to 1.
4.4.7 Sampling for performance test. When specified (see 6.2), a bearing assembly or test specimen, or both
shall be selected and subjected to the tests specified in 4.6.6.
4.5 Inspection.
4.5.1 Visual inspection. Sample bearings shall be visually inspected in a strong light for separation at the
interface between the surface rubber face and the backing material. If separation exists, the sample is to be
considered to have failed the visual inspection. Defects such as roughness, holes, cuts, gouges, bubbles, large
dimples, molding imperfections or tears in the rubber facing material that would indicate a bearing of poor
workmanship, handling, or quality shall also be cause for rejection of the sample. Defects, except bubbles, less than
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