<P> The use of a coped joint for interior corners saves the trouble of having to determine and cut the exact inside degree measurement, since most corners are not exactly 90 / 45 degrees . Outside corners must be mitered, and care must be taken in measuring and cutting, since not all outside corners measure true . If the angle is not exactly 45 / 22.5 degrees, a corner measuring device or piece of scrap crown molding may be used to obtain the right measurement before the final cut is made . </P> <P> Fitting crown molding requires a cut at the correct combination of miter angle and bevel angle . The calculation of these angles is affected by two variables: (1) the spring angle (or crown angle, typically sold in 45 degree and 38 degree formats), and (2) the wall angle . </P> <P> Pre-calculated crown molding tables or software can be used to facilitate the determination of the correct angles . Given the spring angle and the wall angle, the formulas used to calculate the miter angle and the bevel angle are: </P> <Ul> <Li> Miter angle = arctan ⁡ (sin ⁡ (spring angle) tan ⁡ (wall angle / 2)) (\ displaystyle = \ arctan \ left ((\ frac (\ sin (((\ text (spring angle))))) (\ tan (((\ text (wall angle / 2)))))) \ right)) </Li> <Li> Bevel angle = arcsin ⁡ (cos ⁡ (spring angle) ∗ cos ⁡ (wall angle / 2)) (\ displaystyle = \ arcsin \ left (\ cos (((\ text (spring angle)))) * \ cos (((\ text (wall angle / 2)))) \ right)) </Li> </Ul>

How to determine spring angle of crown molding