MIL-HDBK-660B
c. Fill the waveguide with light oil (such as SAE 10), cover the top end, and move the guide about so as to splash the oil on all interior surfaces. Then pour out the oil, leaving 1 or 2 inches in the bottom of the guide.
CAUTION: CAREFUL ATTENTION TO OILING IS NECESSARY TO PREVENT THE ALLOY FROM TINNING THE GUIDE, MAKING CLEANING VERY DIFFICULT
d. Fill the guide with the melted alloy, allowing the alloy to run down the side of the guide in order to avoid air pockets.
e. Immediately lower the filled guide into a quench tank containing rapidly circulating cold water, leaving it there long enough for the guide and alloy to reach tank temperature throughout.
NOTE: Rust-resistant iron or corrosion-resisting steel is required for tank construction. Plain steel will rust when in constant contact with boiling water and steam (formed during initial contact of hot guide). Copper, aluminum, and galvanized iron tank will contaminate the alloy.
f. Remove the filled guide and rewarm it in hot water to about 90 F to 100 F. Remove the wooden plug from the bottom of the guide. The guide is now ready for bending and twisting.
IMPORTANT: Good results with alloy fillers depend entirely on rapid quenching, adequate cooling and rewarming before bending.
4.3.2 Rosin method When rosin is used as a filler, the guide must first be annealed and then filled as follows:
a. Estimate how much rosin is needed to fill the guide. Melt the rosin. Melting is usually done in a vat by means of steam coils.
CAUTION: IF OTHER MEANS OF HEATING ARE USED, BE SURE TO HEAT THE SIDES OF THE CONTAINER FIRST. TOO MUCH HEAT APPLIED AT THE BOTTOM WILL CAUSE AN EXPLOSION.
b. When the guide has cooled (after annealing) just enough so that it will not burn wood, drive a wooden plug in one end, place the guide in an upright position with the plugged end down, and fill with melted rosin.
CAUTION: IF THE GUIDE IS COLD, THE ROSIN WILL CONGEAL WHEN POURED FORMING AIR POCKETS WHICH WILL CAUSE THE GUIDE TO CAVE IN DURING BENDING OR TWISTING.
c. Allow the guide to cool naturally; then look for a cone-shaped hole caused by contraction of the rosin cooling at the top end of the guide. If the hole is deep, add melted rosin and allow to cool; if not very deep, fill with loose rosin.
d. Plug the top end of the guide with a wooden plug. The guide is now ready for bending and twisting. NOTE: Wrinkles may be hammered out before removing the filling, because rosin when powered by hammer
blows, expands and occupies more space than solid filling.
4.4 Bending fabrication. Bending can be done by using a Pines bender, Wallace bender, hydraulic push press, portable pipe bender, hand bending machine, or bench vise. The Pines and Wallace benders do not require fillers for bending. Precise metal-forming operations on the Pines and Wallace bending machines provide smoother bends
than with other types of benders. Greater precision is obtainable with the Pines bender than the Wallace bending machine. Shorter radii bends can be formed on the bending press but with accompanying guide deformation reducing the cross section area inside the bend. Double ogee curves formed by a consecutive series of bends are preferred to the use of several 90 degree elbows. Better electrical characteristics may be realized if the mechanical
tolerances on the guide are maintained in bending complex forms.
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