anglelumberwoodwoodworking
According to the instructions, I have to make a 21.5 degree cut in a 2×4 piece of lumber.
Here’s a screenshot of the instructions:
My question: can this measurement be done without having to buy a protractor or any other specialized tool?
Or even better, can I print out a protractor from the web?
Try this little trick.
Cut two rectangles from your plywood an inch or two larger than what you want your finished pieces to be. Be sure one face of these rectangles are a straight factory edge.
Now stack the two pieces together and clamp them with the factory edges one on top of the other, nice and flush.
Scribe a perfectly square line using a builders square perpendicular to the factory edge on both sides separated by the dimension you want the piece to be.
Now take a perfectly straight piece of wood and clamp it onto the surface exactly at the dimension of the distance of the edge of your blade to the edge of the saw frame. You now have created a guide to run your saw against while making a cut through both pieces of plywood at the same time.
Repeat this procedure on the other side.
For the last cut parallel to the factory edge, measure precisely the distance and mark on either side, draw a line between the marks. This line should be square to the end cuts and parallel to the factory edge.
Now reattach the cutting guide at the blade to frame dimension as you did for the edges and cut both pieces at once again.
You have now made three cuts, two at a 90 degree to the factory edge and one parallel to the factory edge. Since both pieces were cut at the same time, they should be identical.
Cutting a miter like that is best done on a table saw with a crosscut sled, or with a well tuned miter saw, or (failing either of those options) rough cutting the miter with a hand or circular saw and then dressing them with a hand plane or large disk sander. Given the dimensions your best option at this point is to use what's called a "donkey ear shooting board" (shown here) with an appropriate hand plane on a good solid workbench. For best results you will need a fairly sharp low-angle jack plane to perform this operation but it can be done with a standard jack or jointer plane if they are very well tuned. Best of luck!
Best Answer
As pointed out in the comment, you can of course do it with a basic triangle calculator.
Do yourself a huge favor and buy a speed square. They are $10 and are useful for so many things beyond just marking an angle on a board.