The saying goes, “Necessity is the mother of invention.” This idea came about as I was wondering how to lay out large-radius arcs on a workpiece. I don’t own a beam compass or trammel, but I did have a spare length of T-track. After some quick work making a couple of “heads,” I was in business.
The trammel heads are made from hardwood. The vertical holes are sized to fit a pencil and aluminum rod. To sharpen the rod, just chuck it in the drill press and file it to a point. A through hole accommodates the flange bolt that secures the head to the T-track.
A narrow hardboard “key” on the back side keeps the block from twisting out of position. Finally, a quick trip to the band saw creates the kerf that clamps the pencil and rod tight. As an added feature, I fastened a tape measure to the side of the T-track to serve as a handy reference index.
