How to Cut Crown Molding Flat

There are multiple ways to use a compound miter saw to cut crown molding. Although it has become common practice to make vertical cuts while propping up the stock, it’s actually much easier to cut crown molding flat (as in laying flat on a compound miter saw). It may seem like a self-explanatory concept but there’s actually much more to the process than making a few 45-degree cuts. Below is a step-by-step guide to save some time and a lot of frustration when cutting crown molding.

Step 1: Double-Check the Measurements
There is a common misconception about angles. Most people think that, since any room is a rectangle, it must have 90-degree angles. Well, the truth is that no construction job is perfect. At least one of the angles is bound to be off by a degree or two. The trick to doing this job right the first time is making sure all measurements are correct. If you must, check the angles 3 times but double-checking them is a must-do.

Step 2: Do the Math
Now you have to figure out the bevel and miter angles at which to cut the molding. There are specialty tools you can buy that will make this process quick and easy. Alternatively, here’s a sequence you can use to figure the angles out using a scientific calculator:

Enter this sequence to find the right adjustment settings

Miter Setting Bevel Setting
1. ’Measured angle’ [multiply] 0.5 = ‘X’ 1. ’Measured angle’ [multiply] 0.5 = ‘X’
2. ‘X’ [TAN] = ‘Y’ 2. ‘X’ [cos] = ‘Y’
3. ‘Y’ [multiply] 5.5 = ‘Z’ 3. ‘Y’ [multiply] 3.88 = ‘Z’
4. 3.88 [divide] ‘Z’ = ‘N’ 4. ‘Z’ [divide] 5.5 = ‘N’
5. ‘N’ [INV. TAN] = Mitter Adjustment 5. ‘N’ [INV. TAN] = Bevel Adjustment’

If you don’t have a scientific calculator handy, you can still use the “cheat-sheet” table:


Step 3: Mark the Mouldings
It can be easy to forget or even confuse the inner and outer sides of each piece of molding. To avoid that, mark each piece with a marker, so you end up with every piece labeled “outside right”, “outside left”, “inside right” or “inside left”. The “inside” pieces should always be cut to the left of the saw blade, while “outside” ones are to be cut on the right – writing that down on the back of molding is also a good idea.

Step 4: Cut, Paste, Polish!
This is what compound miter saws are made for – put each piece on the table and slowly angle the saw. That’s all there is to it

PRO TIP: After you put up your crown moulding, you may discover that the pieces don’t match perfectly among each other. Luckily, there’s an easy fix: instead of micro-adjusting the angle for perfect corner joints, which means starting from scratch, use a bit of caulk and/or wood putty to “create” a bit of extra corner length.

[IMG VIA: lowes]

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