What angles do I set for a compound miter?
Type the angles off the print. Get the miter and bevel to set on the saw for each piece.
Set the saw to
0 miter
0 bevel
Flares out or leans in, the cut is the same. Outside face up.
Blade tilts left. If yours tilts right, swap left and right on the bevel and the kept end.
Most miter saws swing to about 50°. Check that yours reaches this.
How this was worked out
Assumes a saw whose blade tilts left, with the piece flat on the table, outside face up. Make a test cut on scrap first. Saws read angles differently.
-
About compound miters
A compound miter is two angles in one cut: the miter (the table swung left or right) and the bevel (the blade tilted). Tube, pipe, angle, flat bar or channel lying flat in one plane only needs the miter. You need both when the sides slope, like a hopper, a tapered frame, or a rail turning a corner on a slope.
The corner angle is the angle on the print between two pieces: 90° for a square corner, 120° for a six-sided frame, 135° for an eight-sided frame. Each piece turns half of what is left of 180°. A piece that lies flat takes all of that turn as miter. A piece that stands straight up takes it all as bevel. Anything in between splits it.
Sloped sides, with the blade tilting left and the outside face up, are set up like this:
Left piece: miter left, the narrow-end edge against the fence, keep the right end.
Right piece: miter right, the wide-end edge against the fence, keep the right end.
Flares out or leans in, the cut is the same. Outside face up.
Blade tilts left. If yours tilts right, swap left and right on the bevel and the kept end.
The left and right setup follows the compound cut charts printed in Ridgid and Ryobi miter saw manuals. Make a test cut on scrap first. Saws read angles differently.