Open Angle Coping Jig

Below is an open angle coping jig Forum Technical Advisor Gary Katz uses to cope corners. It enables the crown to turn to the angle of the cope, so the blade on your saw can be held plumb - which is the easiest way to cut a cope without wasting energy on over-backcutting. Even then you need a really long blade, and a lot of patience. For short runs, Gary miters them and pre-assembles the corners with nails and glue.

Readers are reminded to evaluate the significance and the limitations of the information provided below, and consider the responsibility they assume when applying the information for their own use.

JeffeVerde

"For short runs, Gary miters them and pre-assembles the corners with nails and glue" Hunhh? I must be missing something. You show the jig mounted on a saw horse, that's, let's say, 3' tall. Set the jig at 45º (so the cope cut is plumb), allow 6" of molding to project past the jig, and Pythagoras says you can fit a maximum 5' piece of molding in this set up. Unless you're restricting yourself to installing crown molding in coat closets, that doesn't sound particularly useful.

My understanding is that Gary copes pretty much ALL inside corners. One might go so far as to say that Gary *evangelizes* inside copes for their ability to deal with out-of-square corners. I know that Gary miters and pre-assembles (2P-10 glue) his OUTSIDE corners where possible, and I suspect the author confused the two.

For cutting copes, I use a simple jig like the attached picture, which holds the molding horizontally at approximately the proper spring angle - basically the way it goes on the wall. I primarily cut my copes with a jigsaw and Collins coping foot, but I use the same setup when using a coping saw.

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Craig Gardner

Member

All these tricks trying to re-invent the wheel I've never had trouble just using a coping saw holding the crown or base or what have you on a work table!

Gary Katz

Member

Jeffe, That jig is for coping walls at 135 degree angles (some people call them 45 degree inside corners but they're really 135 degrees and the miter is 67 1/2 degrees. I say all of this only to be sure we're on the same page). Most often, those pieces are pretty short - like the returns on a bay window or popout. With a tall workbench, there's usually room to make the cope cut, but the whole process is not fun. While David Collins says all inside corners should be coped, I prefer to pre-assemble those nasty 135 degree corners, mitering them and clamping them while the glue sets. And honestly, if the pieces are long, then I'll just assemble the miters right on the wall. Work isn't a bad word except when it's hard work. I try to avoid that. :) Gary

michael moore

This is basic trim work. You don't need a special set up to cut copes. I've been coping crown for 15 years with just a normal jigsaw with the foot taken off. Long blade, careful to keep the blade follower bearing from touching. I've always just clamped the piece to the miter saw table. If you sight the crown in plane with the ceiling flat (the part that actually bears on the ceiling), you will see if you have backcut enough. Unnecessary after a few rooms, you will feel develop muscle memory. I will say it is best to learn with a manual coping saw so that you develop the feel for the cut geometry with the least amount of blade binding.
Michael