How to Make a Coped Joint

Learning coping techniques will improve your carpentry skills.

A cope is the preferred method of joining two shaped pieces of molding on an inside 90 degree corner. The end cut of the coped piece mirrors the profile of the face of the molding and allows it to fit precisely against the adjacent piece. This proven carpentry technique allows a tight joint that will not open up with shrinking and swelling of the wood due to changes in humidity.

Things You'll Need

• Miter saw
• Coping saw
• Set of small wood rasps or shaped files
• Utility knife

Instructions

Coping Base, Base Cap, Chair Rail, Shoe or Quarter Round

1. 

   A powered miter saw will make cutting the 45-degree cuts more accurate.

   Make a 45-degree open mitered cut (viewing from the front of the molding, the back material of the wood will extend beyond the face of the cut) on the end of the piece you want to cope.

2. Shade the edge of the cut with a pencil lead to darken it and make it more visible. This will be the line which will guide your cope, leaving the face and the mark intact.

3. Position the board so you are holding the saw with your preferred hand toward the cut end. Tilt the coping saw at a 45 degree angle so it will cut along the side of the mark, removing excess material extending behind the face of the molding. Begin the cut from one end, carefully avoiding over cutting and removing the mark. Chip away excess material as you cut if needed to keep the saw from binding, and change directions of your cut for access to difficult shapes or to improve the angle of the cut. Continue to cope until you have cut along the entire shape.

4. 

   Shaped files or rasps are important to getting a good cope joint.

   Use the files to clean up the shape to match the mark, using a scrap of the molding to test the fit. Back cut (cutting material from behind the face) further as needed using the files or a utility knife to make sure the pieces come together at 90 degrees with no gaps in the joint. This step will often take multiple attempts per cope.

Coping Crown Molding

1. Place the crown in the bed of the miter saw upside down and at the same angle in which it installs and cut an open 45-degree miter. The bottom edge of the crown should be the longer point if the cut is correct.

2. Darken the edge of the cut with a pencil.

3. Using the same techniques as in the previous Steps 3 and 4, cut away the excess material and clean up the cope till it fits a scrap piece of the crown tightly. Be sure to position the test pieces in the same orientation as the crown installs in order to check the accuracy of the cope.

Tips & Warnings

• Cut the coped end of your molding first, and after you are satisfied with the fit, then measure and cut the other end to the desired length.

• Have help to hold long pieces in the saw correctly to get an accurate mitered cut.

References

• Workbench: The Case for Coped Joints
• Home Depot: Project Guide: Cutting a Cope Joint on Crown Molding
• The Family Handyman: How to Cope Joints