Drilled and tapped one end of a flap pushrod 5/16 round tube. I’ve seen other builders clamp the pushrod in a drilled wood block, then clamp it in the drill press to do this job. I didn't think that looked very secure so I set one up with partially disassembled flaring tool, which is actually designed to hold tubing. To let the drill self-center, I clamped a couple of square aluminum tubes to the drill press table and placed the flaring clamp between them to prevent free rotation (photo 1). Worked like a charm!
