Incra makes a standard protractor more useful. Rather than trying to mark next to a tiny line on the edge of a protractor, every 5º and every 22.5º they machine long slots for marking lines with a really sharp pencil or a 0.5 mm lead mechanical pencil. For less frequently-used angles they also cut short slots every 1/2º.
Instead of trying to line up the protractor along an edge, you can quickly butt the protractor’s T-bar against the edge of your work piece. When you need to use the protractor in the middle of a piece, the T-bar detaches with two thumb screws. With the T-bar removed, you also have access to a 6″ ruler with marking holes every 1/32″.
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Here’s an oddball — a protractor designed for setting an aircraft propeller’s pitch angle. Apparently these large, high-precision protractors and levels are used for dialing in propeller settings. You set the hub to vertical, the blades (initially) to horizontal, then adjust until you reach the desired angle. Given how critical wheel balance is on a car, I can imagine you’d need a pretty special tool to dial in faster-spinning propellers. They’re not exactly a failure-tolerant par, and neither are control surfaces, which this device can also be used to adjust.
As evidence of how important propeller settings can be, there are versions of this tool available for as much as $1,470, though the swanky transparent body may have something to do with that. Warp Drive manufactures the plastic model above, and retails it for a much more reasonable $39 before shipping from Aircraft Spruce. It’s a niche tool, but probably a crappy thing to be stuck without.
I was trained as a machinist, and finding angles always drove me up the wall. For some reason, I find it really hard to trust my own math when creating fixtures with Joe blocks and sine plates, and wind up verifying everything seven ways. Denali has a little something that may take the sting out.
While digital protractors like this have been around for a while, it’s hard to pass up Amazon’s $23 price on this one. Strictly speaking, it may not be accurate enough for precision work, but +/- 1 degree is more than enough for woodworking and sheet metal layout. +/- 1 degree is probably the best you’d get with a steel protractor. More accurate versions are available from Bosch, but ninety percent of the time, Denali’s little 11-incher should be plenty, and it’ll save you a lot of close-up guesswork.