MIL-DTL-85K
4.5.3 Twist (see 3.5). The angle of twist of waveguide shall be measured as shown on figure 1 and as
follows:
a. The waveguide shall be placed on a flat, horizontal reference plane. Waveguides with
noticeable, flatwise, bow shall be positioned with the waveguide surface on the side of the
convex curvature in contact with the reference plane.
b. One end of the waveguide surface shall be held in intimate contact with the reference plane by
suitable means while the other end of the waveguide remains free.
c. Using an engraved, transparent, protractor segment, determine the angle line on the protractor
which coincides to the nearest degree with the surface of the waveguide, while one edge of the
protractor segment contacts, or is kept parallel to the reference plane by means of parallel face
blocks.
4.5.4 Squareness of cut (see 3.6). The squareness of the cut of the waveguide shall be measured
using an adjustable protractor.
4.5.5 Surface roughness (see 3.7). The average interior surface roughness of the waveguide shall be
measured in accordance with ASME- B46.1, except flaws shall be included in the surface roughness
measurement and the corner radius shall not be included in the measurement. Unless otherwise
specified (see 3.1 and 6.2), surface roughness shall be measured across the grain over the full width of
the waveguide interior surface, at the center of the waveguide length and 6 inches from the end of each
length.
4.5.6 Pressurization (see 3.8) (unless otherwise specified (see 3.1), applicable to fabricated waveguide
only). The waveguide shall be subjected to the internal air pressure, in pounds-force per square inch
2
(lbf/in ), specified in table VII while immersed in water for at least 5 minutes. The water temperature shall
be 68°F ± 10°F. Any bubbles coming from the edge seams of the waveguide shall be considered as
leakage. Bubbles that are the result of entrapped air on the exterior surface of the waveguide shall not be
considered as leakage.
TABLE VII. Pressurization.
Inside width
Wall thickness
Pressure
(nominal)
(nominal)
Inches
Inches
lbs-force/square inch
23.000
0.188
0.25
21.000
0.188
0.25
18.000
0.125
0.25
15.000
0.125
0.25
11.500
0.125
0.50
9.750
0.125
0.50
7.700
0.125
1.0
6.500
0.125
1.5
5.100
0.080
2.0
4.300
0.080
3.0
8
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