Find a source for a Stay-Brite Silver Solder Kit. Includes a small spool of solder and a squeeze bottle of acid flux. Brighten the rod surface with sand paper, steel wool, or whatever. Support the work so that your clevis is properly aligned with the rod. Add a drop or two of flux to the joint. Apply heat to the joint with a 30 watt or greater soldering iron. You'll hear the flux bubble while it gets up to temp. Touch the joint with the solder and watch the solder wick into the joint - feed enough solder in to get complete coverage. It's fun! Let it cool on its own, no blowing on it. After it has cooled, wash the work with soap and water so that residual flux doesn't cause unsightly corrosion.

This will yield a very strong connection - I can't imagine that a threaded clevis would provide more strength than a properly soldered joint. It also provides a lot of flexability in making up just the length of control rod you need. My own crash testing has shown that you can pull a threaded clevis off of a rod but I have never had a solder joint fail.

Rich