Compound Miter (Crown Molding)
Saw settings to cut crown molding flat on the table: 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).
Formula and source
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.
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