Step 3: Mic Assembly
The boom's length is adjustable and the mouth piece rotates on its axis. The entire mic assembly rotates around the ear cup. This adjustability is needed so that the user can use the headset on the right ear or left ear.
Using a hacksaw, cut off about 3/16" from the 1/2" copper end cap. Drill a 1/8" hole dead center. Drill a 5/16" hole in the side of the cap so that the edge of the hole is toward the edge of the cap.
Take one of the 1/8" copper caps and drill a 5/32" hole dead center of on the face. Cut off about 3" of 5/32" brass round tube. Fit the brass tube inside the 1/8" copper cap and then both into the 1/2" copper cap. Using a soldering torch or large solder iron, sweat solder all three pieces together. You can see in the photo I made a simple jig to make sure everything lined up squarely while soldering. The mic fits inside the 1/8" copper cap. Glue the mic into the place using silicone adhesive.
The adjustable part of the mic boom consists of the 1/8" copper piping approx. 2 1/4" long. One end is capped by an 1/8" elbow the other with a 1/8" cap. The cap needs to be drilled dead center, 1/8" dia.
The next part is to make the bushings. I made a very small leather washer that fits inside the 1/8" cap. The other bushing is a small strip wrapped around the 5/32" brass tubing. The leather acts as a kind of piston inside the 1/8" copper piping. All these bushings are intended to provide a tight fit so that the boom doesn't flop around. I provided a diagram that shows how this all fits together.
Note, when doing the final assembly of the boom, make sure the cap and the leather washer are slid up on the 5/32" brass tube before you wrap it with the leather to form the "piston."