yankeewoodworker

I put up a lot of crown a few years ago when the economy was purring. We were spoiled in some ways: where I live there were (still are but not so many) clients with big houses, budgets and pocketbooks so it was critical that we do a good job.
I've tried mitering and there is no question in my mind that coping gets me where we need to be. We live and work next to the ocean so seasonal movement of wood is off the charts. The few times I've tried mitering the joints were open in weeks; with copes I haven't seen them come apart yet.
Layout is fairly straightforward, mapping out insides and outs are obvious, and we plan our cuts so we never get the dreaded double cope. We also always use a backer or nailer board made from spf to catch nails, usually 16 gauge.

Somethings we do that help get good results (I think):
1. Order what we need from the lumber yard. Often I will order 20 % extra and I want the boards to come from one milling. If I pick the lumber then i will only choose sticks that are coming from a bundle and not outside of it.
2. Use the Bosch digital protractor to check corners for 90's. For outside corners it's a good way to anticipate a back cut while you still have the stock to do it.
3. Install nailers. Rip 2 x 4 or 2 x 6 in two on bevel. Check crown to determine bevel angle and leave 1/4" between back of crown and nailer for wiggle and twist room. We nail and glue these up fast- leave a space for the butt joint of non-coped inside piece.
4. We use the table saw method to hog out the cope. I finish off the copes with my dremel and piece of fine sandpaper.
5. I plan my scarfs or joints of two pieces for the end of the day. this gives overnight drying of epoxy and the boards aren't in anyone's way during the night. I set up a straight workstation of horses or whatever to support the pieces. I then use west system with a 30 deg scarf cut. I cut 3/16" shims to hold the joint, clamp, glue and shoot 18 gauge short nails to hold the shims and hand sand in the morning to get the face of the joint perfect.
6. I find the only way to get good, consistent results means to take a half hour and build a plywood jig to hold the crown on the miter saws. Here's where you appreciate the movement of wood when you go to get the measurement of widths for your crown. I take 10 measurements and arrive at a mean. I find a piece that represents that mean, check to make certain it isn't cupping and lay out a 90 degree jig with a stop at the top so the wood can't creep when I'm holding it up to get cut. The jig is well worth the effort.
7. We use blocks to lay out marks that we will then use a chalk line to connect. The blocks are for the wall- height portion of the crown, the chalk is to anticipate the waves when they come. Occasionally the plasterers have given us some pretty badly faired sections and in these instances I will scribe out with a block plane a portion of the back of the crown to hide these inconsistencies as well as possible.