The Curiously Strong Trebuchet: A Pocket Sized Medieval Siege Engine

Step 4 Drill Holes in Couplers

First, draw a dot with a Sharpie 2/3 of the way up from the bottom of the bottom of both couplers, in the center of one of the hexagonal flats (see first picture). Next, set the coupler on an anvil (or on any other surface you don't mind banging on really hard) and tap a small indentation on the dot with the center punch. Put some oil in the hole, and clamp it into the vise. Using a electric drill (you could use a cordless, but it goes really slow), drill straight through to the coupler. Repeat these steps with the other coupler. They are never going to be perfect so just try your best. They should look like the second picture when you are finished.