Forest. River. Rocks. - Sector Build

What is a Sector? Here's an excerpt from Lost Art Press, where free instructions and template are available to download:

If you haven’t heard of the sector, it probably means you aren’t an artillery officer or a ship’s navigator working in the 17th century. An invention attributed to the great astronomer Galileo, the sector was a calculation instrument comprised of a pair of hinged plates engraved with a variety of scales that – coupled with a pair of dividers – enabled the operator to calculate proportions, polygons, trigonometric and numerous other table functions.
— Lost Art Press

While I could have made one out of paper and laminated it, I decided to make one out of scraps of poplar.

I started with a print-out of the template from Lost Art Press and used it to transfer the shape of the tool to the wood.

A bow saw and some file work made quick work out of shaping it.

For the rounded top where the two sides of the sector are attached, I used some carving tools to carefully reduce the width. Then I drilled a hole through each piece to fit a brass screw I had on hand.

With the paper template as a guide, it was pretty easy to map out the lines and points on the wood. Then I used a punch to mark the points. These points are where the compass registers to make calculations. The markings are done with sharpies.

That's it. Not much to it, really. But what an incredible tool for laying out stock and accomplishing other dimensioning. Someday, I may splurge and get a professional model. I found this beautiful Sector from Acer-Ferrous Toolworks that is both pricey and beautiful. Here's another lovely Sector from burnHeart.