When starting in woodworking I couldn’t afford a good set of trammel points. I had my grandfather’s set, but it didn’t lock down well. Then one day woodworker Troy Sexton showed me how he drew large arcs and I realized that I already owned an effective trammel.
Troy uses a yardstick (or meter stick if you are metric). Then he bores holes at all the locations where he wants to draw arcs. And he has a hole bored at the 1” mark. He puts a thumbtack or nail in the hole at 1” and a pencil in the other hole.
The only hitch is, of course, that you need to account for the pivot hole being at 1”. So if you want a 10” radius, you need a hole at 11”.
Today I needed to strike arcs with a 10” radius for a stool I’m building and I used my old aluminum yardstick (which I’ve had since I was a kid) to make the arcs.
To make a new hole for a new arc, first take a centerpunch and dimple the yardstick at the exact location for the hole – the punch prevents the drill bit from wandering when you make the hole. Then drill a hole using a 1/16” bit, which fits the collar of a mechanical pencil.
The rest is simple. Put a thumbtack through the 1” hole at the center of the radius. Put a pencil in the 11” hole and strike the arc.
You can, of course, do the same thing with a strip of wood, but I like using the yardstick because I’m less likely to use the wrong hole or throw away the tool by accident.
— Christopher Schwarz