How to Cope a Mitered Joint for Crown Molding

The installation of crown molding can be facilitated through the use of coped miter cuts at all inside corners. The effective use of coped miters allows the home carpenter to compensate for out of square walls and ceilings that are common place in many houses as the the coped miter is an effective means of adjusting the corner cut to fit the existing profile of the previously installed intersecting piece of molding. Coped miters eliminate caps and improperly fit corner joints.

Difficulty: Moderate

Instructions

Things You'll Need:

• Miter saw
• Coping saw
• Combination round and flat face rasp
• Pencil
• "C" clamp
• Vise
• Crown molding

1. 

   Cut an inside miter using the miter saw.

2. 

   Position molding in the vice with the cut face up and use rasp to smooth any rough surfaces.

3. 

   Check the miter cut to ensure that the cut face reveals the profile of the molding. Then using a dark leaded carpenter pencil darken the profile of the molding by marking the profile with a heavy pencil line.

4. 

   Using the coping saw begin cutting on the back side of the molding by cutting parallel to and 1/16 inch from the previously drawn profile line. During this cut the coping saw blade must be angled at approximately 45 degrees to the back face of the molding. This ensures that most the molding is removed near the face of the molding and gradually less molding is remove as the cut progresses to the back side of the molding.

5. 

   Continue cutting within 1/16 inch of the profile line turning the coping saw as necessary to negotiate changes in the angle of the profile line.
   Once the angle changes become too sharp to negotiate with the coping saw remove the saw and make vertical cut from the back of the molding towards the face. Cut until the previously cut profile line is intersected. This will allow removal of the previously cut wood from the back side of the molding.

6. Begin a mew cut at the point at which the prior vertical cut ended. Continue to cut within 1/16 inch of the previously drawn profile line. Should the profile angles become too sharp to negotiate, repeat Steps 5 and 6.

7. 

   Complete cutting the profile of the miter face and then use combination rasp to to smooth rough edges and further delineate the molding profile. Use the round face of the rasp to smooth rounded profiles and the flat face to sharpen angled profiles in the molding .

8. 

   Test fit the coped miter by positioning it in place against the previously nailed molding on the intersecting wall.

9. 

   Use carpenter pencil to mark any point at which additional molding must be removed to close gaps existing between the two joined corner pieces. Use the rasp to cut away additional material on the back side of the molding profile until the gap is closed.

Tips & Warnings

• Coped miter joints are used for joining inside corners of crown molding as these compensate for out of square wall and ceiling placements. The coped joint is always matched and joined to a previously installed butt joint in which one unmitered end of crown molding is butted into a corner and is nailed in place. The coped joint is then cut to fit the profile of butt end molding already in place.
• When coping the molding profile maintain the 1/16 inch gap between the face of the molding and the profile cut line to avoid cutting into the face of the molding.