newbie basic miter question

When making a 45 degree cut, the longer edge will extend 1.414 * Thickness / 2 further than the short edge. In your drawing, the short side was 6 feet long. There are two 45 degree cuts, adding 1.414 *

The much easier way to do this is to cut one side at 45 degrees and just mark exactly 6' on the back of the board (or better yet, hold the board up to the wall and mark the length EXACTLY). Then cut from the front side being very conservative and leaving yourself some extra length. Then flip the board over and see how close you got to the pencil line. Flip it back to the front side and cut off a little more. Repeat until you get to the exact correct length on the back.

Also, assuming you have a 10" miter saw (and it IS compound if the blade bevels, even in only one direction), you should be able to stand the molding up on edge and, therefore, only have to rotate the table, not change the bevel. You should always keep the front side of the molding facing outwards (towards you), since there will likely be some chipout on the back. If you'd prefer to keep the board flat and tilt the blade to 45 degrees, you should make all of your cuts with the outside facing up, again to isolate chipout to the back side.

WRONG. When making a 45-degree cut, the longer edge is longer than the shorter edge by exacly the thickness of the board. In his drawing with two 45 degree cuts on a 1.25" board 6' long, the total length will be 6' + (2 * 1.25) =

Yes; I feel like an idiot (Luckily, not a first for me). I apparently needed some coffee.