MIL-DTL-85 Waveguides, Rigid, Rectangular General Specification ForThis specification covers the performance requirements for seamless or fabricated rigid waveguides with rectangular inside configurations \(see 6.1\).

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MIL-DTL-85K

3.2.2.1 Copper alloy. Copper alloy shall conform to commercial bronze, 90 percent, of ASTM-B372.

3.2.3 Magnesium alloy. Magnesium alloy shall conform to the chemical composition and tensile

property requirements for alloy AZ31B of ASTM-B107/B107M.

3.2.4 Silver alloy. Silver alloy shall conform to the chemical composition requirements for coin silver.

In addition, silver alloy waveguides shall be furnished in the drawn temper with a Rockwell hardness of

45.0 to 80.00 on the "B" scale.

3.2.5 Silver-lined copper or copper alloy. Silver-lined copper or copper alloy shall be copper (see

3.2.2) or copper alloy (see 3.2.2.1) laminated with a minimum of .005 inch of fine silver.

3.2.6 Copper-clad invar. Copper-clad plating shall be of .003 to .007-inch thickness on both inside and

outside surfaces.

3.2.7 Dissimilar metals. Unless suitably protected against electrolytic corrosion, dissimilar metals shall

not be used in intimate contact with each other.

3.2.8 Pure tin. The use of pure tin, as an underplate or final finish, is prohibited both internally and

externally. Tin content of waveguide components and solder shall not exceed 97 percent, by mass. Tin

shall be alloyed with a minimum of 3 percent lead,

3.3 Design and construction. Waveguides shall be of the design, construction, and physical

dimensions specified (see 3.1).

3.3.1 Finish. The interior and exterior surfaces of the waveguide shall be bright, smooth, dry, and free

of scales or oxide.

3.3.2 Length. The finished waveguide shall be furnished in 96, 120, 144, and 168 inches (8,10,12, and

14 feet) straight lengths (see 3.1) with ends. The shortest permissible length of the ends shall not be less

than 60 percent of the nominal length (specific and stock) and the maximum permissible weight of ends

shall not exceed 25 percent of the lot weight. Waveguide tube, ordered to specific or stock lengths, with

or without ends (see 6.2), shall conform to the tolerances in table I.

TABLE I. Length tolerances.

(Applicable only to full length pieces)

Tolerance,

Length

inch

(all plus)

Standard (stock) - - - - - - - -

Specific

Up to 14 foot, inclusive- - -

.25

Over 14 foot - - - - - - - - -

.50

3.3.3 Perpendicularity. Perpendicularity is the deviation from a right angle of two adjacent interior

waveguide surfaces. The deviation shall not exceed .008 inches per inch (0.5 degree) when measured at

each end of the waveguide length (see 4.5.1).