MIL-DTL-85K
any two points 2 feet apart on the concave external surface shall not be more than .010 inch on the
narrow surface (E-plane) and .020 inch on the wide surface (H-plane). If the waveguide is less than 2
feet long, the allowable bow shall be proportionate to the above requirements.
3.5 Twist. When waveguides are measured as specified in 4.5.3, the maximum twist along the
longitudinal axis shall not exceed 1 degree per foot of length on the face of the interior or exterior
surfaces.
3.6 Squareness of cut. When measured as specified in 4.5.4, the departure from squareness of the
end of any waveguide shall not exceed 0.010 inch (0.25 mm) for waveguides up to .625 inch (15.88 mm)
maximum inside waveguide dimension, inclusive, and 0.016 Inch (0.41 mm) (1 degree) for waveguides
over .625 inch (15.88 mm) maximum inside waveguide dimension.
3.7 Surface roughness. When measured as specified in 4.5.5, the interior surface roughness of the
waveguide shall not exceed the values shown in table II.
TABLE II. Surface roughness tolerances of waveguides.
(Microinch RMS)
Allowable surface roughness
Specified major inner
maximum arithmetic average (AA)
dimension (inches)
Aluminum, aluminum
Copper, copper alloy,
alloy and
silver alloy, silver-lined
magnesium alloy
copper, silver-lined
copper alloy, and
copper-clad invar
Up to 4, exclusive - - - - -
63
32
4 and over- - - - - - - - - -
125
63
3.8 Pressurization (unless otherwise specified (see 3.1), applicable to fabricated waveguides only).
When assemblies are tested as specified in 4.5.6, there shall be no leakage from the edge seams of the
waveguide.
3.9 Voltage standing wave ratio (VSWR) (unless otherwise specified (see 3.1) applicable to fabricated
waveguides only). When waveguides are tested as specified in 4.5.7, the VSWR shall not exceed 1.02.
3.10 Scratches. When measured as specified in 4.5.8, scratches shall not be more than 1 mil deep in
the longitudinal direction of waveguides with internal measurements of .622 by .311 inch or larger. For
waveguides less than .622 by .311 inch internal measurement, the depth of scratches shall not exceed 12
percent of the width of the scratch.
3.11 Marking. Each length of waveguide shall be marked in accordance with method I of MIL-STD-
1285, with the Part or Identifying Number (PIN see 1.2 and 3.1) and the manufacturer s source code. The
manufacturer s name or trademark may also be marked on the waveguide, provided such letters are not
expressly forbidden in the contract or order, and their height does not exceed 50 percent of the outside
dimension of the waveguide. T he markings shall be applied with a permanent ink or paint. Not more
than 6-inch intervals shall be permitted from the end of one marking to the beginning of the next marking.
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