Maker's Notes-Graduation

The Fabrication and Graduation of a "Bronze" Quadrant Using Traditional Tools

In 2002 I found some US Coast Guard 4" diameter pipe at our local metal salvage company. It turned out to be a 5% Ni-Copper alloy of a lovely bronze color with walls about 1/8" thick. I immediately purchased a short length as a source of both metal rings and flatstock. To make the quadrant I cut off a length of pipe 5" long, slit one side and opened it up and flattened it with hammers and a heavy steel flat "anvil." I then sanded one side smooth (an image of the unfinished side can be seen below). I used a punch to prick a mark near the vertex to place one leg of my large dividers to lay out the four arcs seen on the photo of the finished quadrant above. With dividers still set to the largest arc, the first divisions of the arc were scribed as described in my photo essay on graduation of a quadrant. I also drilled a small diameter (1/16") hole at the same punched mark (center of the arc) for the plummet line.

After graduation two slots were made along one edge of the quadrant with a file, carefully cutting them so they just touch the scribed line (90° or 0°) delineating the arc. Small brass sites with identically aligned holes were then fitted and soldered in place with "easy" silver solder. Next, figure punches were used to add the ten-degree graduation numbers. Finally, a small plummet, shaped with files on a lathe, was made and hung from the vertex with a short piece of string.