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

FIGURE 11.  Mandrel setting too deep.

FIGURE 12.  Inherent gap between tangent point and lip of wiper die.

If a plug mandrel cannot provide a good bend before rupture occurs, use a form type mandrel shaped for the curve of the bend.  The plug and form mandrels do not provide sufficient support for the thin wall guide and sharp bends.  The use of a ball mandrel is necessary to extend deeply into the bend (see figure 13).  Formed mandrels may be used as a compromise between the expense of a ball mandrel and insufficient support of a plug mandrel.

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