A drill press and drill jig makes drilling a hole straight through a pole or mast a simple task. The jig holds the pole in place, and the drill press, by nature, places the bit perfectly centered on the round object. But if you don't have access to a drill press and jig, trying to drill that same hole by hand rarely results in a directly centered hole. Radio magazine Editor Chriss Scherer was presented with this obstacle while fabricating some mounts to use on standard speaker stands. He had the ABS pipe and the mounting hardware, but he did not have a drill press. Here's the method he devised to ensure a clean result.
Take a strip of paper longer than the circumference of the pole. Scribe a line across the paper. Wrap the paper around the pole and secure it with tape (1). Make an intersecting mark line with a pencil (2) , then remove the paper strip from the pole without removing the tape (keeping the paper in a loop) (3). Flatten the paper strip along the intersecting mark (4). Make another mark along the opposite fold. Put the paper back on the pole with the marks in the desired location of the holes to be drilled (5).
Using an awl, dimple the pole on the two marks on either side of the pole to prevent the drill bit from wandering (6). Chriss placed the pole in a partially opened vice to provide a stable platform. Drill a pilot hole on each mark through the paper (7). Expand the holes on both sides to desired size.
The result will be a hole drilled directly through the center of the pole (8).
Irwin is RF engineer/project manager for Clear Channel Los Angeles. Contact him at email@example.com.