Jim Tolpin and George Walker’s book By Hand and Eye has been a book I have carried everywhere for the last few months. Some of the Instagram folks have even called it “wizardry” and I have to agree. One of the tools mentioned in the book is a Sector. The Sector is used to quickly make divisions (or multiplications) of any length. Going through the exercises in the book I made a quick paper sector with a couple strips of card stock and a brad. But for use in the shop I wanted something a little more substantial.
I picked up a pair of cheap hinges at Rockler. They come in a two pack so you can make a large sector and a smaller one. The cost is about $12 and the hinges are made in China. I chose these because they were relatively inexpensive and could be easily mortised into the legs of the sector adding some strength.
Keeping to the theme of the book I didn’t use any dimensions. I found a piece of maple that appeared to be around 2 ft in length and was wide enough to get two tapered pieces out of. I squared this up making the thickness about 2/3 larger than the width of the hinge.
The next step was to mark a diagonal line that would create the taper. The tapered edges would then become the outside of the sector. The tapers are not essential but are aesthetically pleasing. After cutting the two tapers I used a hand plane to clean up the sides and bring them to the same size.
I then put the two pieces end to end and lined up the hinge. Once you have things lined up the way you want them, mark around the hinge.
I used a marking gauge set to the thickness of the hinge to mark the ends of the pieces.
Then I used a chisel the same width of the hinge to chop out the waste. When it came to the curved portion of the mortise I switched to a narrow chisel and gently pared around the arc.
I assembled both halves to make sure that the hinges fit flush on the ends and top. Doing it this way meant that I could divide the length from the end of my “stick” instead of from the hinge.
George Walker recommends dividing the legs of the sector into 13 intervals. You don’t measure this. Simply set your dividers to a width that will allow you to create the 13 lines. Once you are satisfied with the spacing, leave a slight impression with your dividers.
You could probably just use a pencil and mark across the points left behind by your dividers, but I chose to use a marking knife so that I could come back with a permanent marker and darken things up over time. Hopefully this will leave a lasting mark. Tip: when you make your marks, set your square to the inside of the sector leg and not the tapered side, otherwise your lines will be off.
At this point the sector is completely functional. However, I’m thinking of adding a mechanism to lock it into place. More to come. Maybe.