MIL-HDBK-660 Fabrication Of Rigid Waveguide Assemblies Sweep Bends And TwistsThis handbook is intended for the electronic installations technician to be used as a guide for fabricating rectangular waveguide bends and twists used in the microwave region of the electronic spectrum.

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MIL-HDBK-660B

5.2 Removal of dents and wrinkles from waveguide. Dents and wrinkles should be removed from the waveguide after the filler has been removed (if the filler is rosin, imperfections may be removed from the waveguide while the rosin is in place). Dents are removed from an empty guide as follows:

a. Seal the guide in the usual way at both ends and fit one end with a valve. b. Fill the guide with air pressure of about 28 pounds per square inch (p.s.i.)

CAUTION: THE AIR PRESSURE MUST BE CLOSELY WATCHED AS PRESSURE EXCEEDING 30 P. S. I. WILL BULGE THE GUIDE.

c. Heat the area around the dent with a torch and remove the dent by means of a flatter. A blow torch should not be used on magnesium waveguide as magnesium material will support combustion after the ignition temperature has been reached.

5.3 Cutting. Cut the waveguide with a hacksaw or a powered metal cutting saw.

5.3.1 Hacksaw. For soft metal waveguides, use a fine tooth blade (10 to 14 teeth per inch). For copper or copper alloy, the guide can be cut with a blade having 20 to 24 teeth per inch.

5.3.2 Power saw. A recommended blade for cutting brass waveguide is the Simmonds T-11 steel blade, or equivalent. It is to be driven at approximately 1,200 revolutions per minute (r.p.m.).

5.3.3 Squareness of cut. The cut should be square and at right angles to the length of the guide. The edges must be filed or ground smooth so that the ends do not deviate from squareness by more than .031 (0.79 mm) of an inch. All fillings, chips, and other bits of metal must be removed from the guide before inserting the waveguide into the flange.

5.3.4 Modification of flanges and heavy wall waveguides for proper fit. There are two ways of modifying the pieces to assure proper fit.

5.3.4.1 Cover flange. Machine the heavy wall waveguide down to the size of the standard waveguide so that it will fit into a standard choke flange (see figure 28).