Compound Miter (Crown Molding)
Saw settings to cut crown molding flat on the table.
Example
You enter
- Spring angle (deg, 38 or 45) 38
- Wall corner angle (deg, 90 square) 90
You get
- Miter angle (saw table) 31.62 deg
- Bevel angle (blade tilt) 33.86 deg
Details, formula, and sources
Miter (table) = atan(tan(corner/2) x sin(spring)) and bevel (blade tilt) = asin(cos(spring) x cos(corner/2)) from the molding spring angle (38 or 45 degrees) and the wall corner angle (90 for a square corner) (first-principles trigonometry; reproduces the standard compound-miter chart).
Crown cut flat on the saw: miter (table swing) = atan(tan(corner/2) x sin(spring)); bevel (blade tilt) = asin(cos(spring) x cos(corner/2)). Spring is the molding profile angle (38 or 45 deg), corner is the wall angle (90 deg square).
Compound-miter geometry for crown molding cut flat - first-principles trigonometry; public domain. Reproduces the standard published compound-miter chart.
Pure trigonometry, public; the spring angle and wall corner angle are user-supplied.
Estimate. AHJ and licensed professional govern.
Field names used by the API: spring_angle_deg, corner_angle_deg, miter_angle_deg, bevel_angle_deg
- Cut flat the molding lies flat on the saw table (not sprung against the fence); the spring angle is the molding's installed angle from the wallcompound-miter geometry