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I'm trying my hand at coping crown molding. I cut a couple of test pieces to try it out but it's not working very well. My first attempt was cutting the miter 45°, that didn't work, the angle was too steep. Then I tried cutting it at 38°, closer but the bottom is open. What am I doing wrong? Is the bevel important?

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Cutting on the flat:

If you are cutting on the flat there are lots of mitre/bevel charts online like this one: Mitre/Bevel Chart

Cutting Nested:

Have you tried nesting your crown?

Hold the crown at the angle it would be on the wall, and just do a normal mitre (no need to worry about bevel).

This is how I prefer to cut it, but everyone has their preferences. You can buy different stops and clamps for setting this up to be quick and accurate (or make your own jig). As well as most saws nowadays have attachments for their saws for this.

Attachment:

Nested Attachment

V.S. Shop-made:

Nested Jig

  • I am cutting it on the flat, so I should be using 31.62? I'll give that a try. – gebuh Apr 21 '13 at 21:10
  • On the flat would be 31.62 mitre and 33.86 bevel if your corners are 90 degrees – ryanwinchester Apr 21 '13 at 23:17
  • Or just 45 degree mitre if you nest it ;) – ryanwinchester Apr 21 '13 at 23:18
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    Don't forget that ceiling is down when nesting.. – HerrBag Apr 22 '13 at 3:06
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This can be calculated

If you have a calculator and like math, you can use trigonometry to get precise angles.

Set your calculator to use degrees instead of radians. Usually it is a button labled "DEG".

Needed Angles

  • S = Spring Angle (the angle from the baseboard to the wall, vertex at the bottom)
  • W = Wall Angle (the angle from the inside of the wall: a room is four 90° angles; a corner is a 270°)

Angles to Find

  • M = Miter Angle (the angle at the flat face of the baseboard, sometimes called the face grain)
  • B = Bevel Angle (270° minus the dihedral angle between the flat face of the baseboard and the cut end's face, sometimes called the end grain)

Here's the Math

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