I am installing crown molding in a guest room. I am using 3 5/8 with a 38 degree spring angle. I used a framing square to determine the height of the molding on the wall and found it to b 3". I want to draw a line on the wall to assist with mounting, but I want to be sure this is correct. I am also having to use 22.5 degree on some corners. One outside corner is around a rounded corner on the sheet rock. It is proving difficult. I determined the actual wall angle to be 88 degrees. What are the bevel and trim angles for my miter saw? Please tell me the angles in degrees that I can find on the miter saw table. It is a Craftsman 10" compound miter saw.

 

There are 2 ways of cutting crown moulding. Flat... and in position (upside down and backward). IMO it is a thousand times easier to do both simple and complicated cuts when you are cutting in position. What this means is that the fence of the saw is like the wall, and the table of your saw is like the ceiling.

You put the crown moulding upside down on the saw and use a 3" tall scrap of wood as a backer behind the crown moulding. (I prefer this method over using crown moulding stops in front of the trim). You know you are holding the crown moulding at the correct spring angle when it is flush with the 3" tall backer board. You can feel when its perfectly flush with your fingers... if its flush, its time to cut. If its not flush, adjust the crown so that it is. Then it is simply a matter of cutting a 45° miter. No bevels to worry about.

On a rounded corner you just need to figure out what size to make the little corner piece. Instead of it being a 2 piece corner (45's) it will be 3 pieces, with 4 miters. 90/4 is 22.5°. So take a long piece and cut the 22.5 on one end, the swing the saw to the opposite 22.5, and cut it about 3/4" wide. When cutting a tiny corner piece, always use a long piece to keep your fingers away from the blade. Use some scraps (cut the corresponding 22.5 on each side) to place on either side to see how it fits and cut a new corner piece until you get one that fits nice. If it really is an 88° outside rounded corner, I think your 4 cuts on those 3 pieces would all be 23°. If it's a 88° corner w/o the rounded corner, it would be 46° + 46°.

Cutting flat is harder for me... I don't want to have to have a freaking chart for every different spring angle and have to look at the chart for every angle I cut. Its also a little hard to be accurate when those charts have decimals and your miter and bevel don't. With big mouldings, it's advantageous to cut flat. With small mouldings, I cut upside down and backwards.

Putting lines on the walls only works if your ceiling is as straight as your line is. I prefer to use a block as a gauge and just make a couple light marks on each corner (-the corner is where you definitely don't want your spring angle to change since that would screw up your miter) and a few here and there in between just as a reference. Rather than making one side of the crown straight as an arrow (which means the other side may look twice as wavy) I prefer to split the difference if there is any waviness, so that you hide as much of it as possible.

 

I agree with X and glad he took the time. Upside down and backwards is better.
I try to cut the 'left' angle first, and then cut the right side of the molding, it's easier to shave off a tiny bit if needed. If done properly, you can get furniture quality cuts, even with finished wood.

For rounded corners, I used to cut the small piece trial and error and see if it fits. I learned to cut several small pieces and see which one fits. For a rounded corner the bottom of the crown usually measures around 5/8 to 3/4". 3/4 is usually too much so you have to dial it in.

 

Thank you so much. I tried the backer board with the molding resting against it and it is so much easier. I do have some trouble holding it tight against the backer board though. When I start the miter saw, the molding seems to jump slightly. I retested the molding and determined it is 2 7/8'" instead of three. I cut the backer to 2 7/8". I then rest the top (bottom) of the molding with the edge flush with the top of the backer. I cut two 22.5 joints and they seem to work fine. When you have the rounded corners, do you have to take some off the back of the molding at the bottom to allow the side to fit flush?

 

No... like Brian was saying, the corner piece is maybe 5/8" or 11/16" wide at the bottom. It sits at a 45° angle on the bullnose, and the other pieces butt up to it. It creates 2 small voids on each side of the bullnose, but they are small enough to caulk. I have never scribed one to fit the bullnose... its just not standard practice to do so.

 

Anyone installing crown should check out these clamps if they haven't seen them before. You can glue and clamp the outside corners. You can also clamp a piece temporarily for measuring purposes. Here's a link:

Collins Tool Co. - Tighter Joints. Quicker Production. Miter Clamp Pliers



AFAIK this is the only company that makes these clamps, I haven't seen them at any store. They make my job a whole lot easier.

 

Gentlemen:

I just want to say a big "THANK YOU". I have now run most of the crown molding and I must say, the method of putting the molding against the fence worked so much better for me. I must admit though, I made the wrong cut on the last piece and will have to get one more piece. That is on me. Thanks again for your help.