To mitre crown molding effectively, particularly for a snug inside corner, you begin by making a precise 45-degree cut on your miter saw. This initial cut then serves as the foundation for either a standard mitered joint or, for inside corners, a more durable coped joint created with a coping saw.
Understanding Crown Molding Mitering
Mitering crown molding involves cutting the ends of the molding at an angle so that two pieces can join perfectly to form a corner. While a simple miter cut works well for outside corners, for inside corners, a coped joint is often preferred. This technique, which starts with a miter cut, allows for a tighter fit that accommodates slight wall imperfections and prevents unsightly gaps due to wood expansion and contraction.
The Initial Miter Cut for Crown Molding
The process begins on your miter saw, specifically preparing the molding for either type of corner joint.
- Orient the Molding: Place the crown molding on your miter saw with its bottom side up. This means the edge of the molding that will rest against the ceiling should be positioned downwards on the saw's fence, and the edge that will meet the wall should be facing upwards, resting on the saw's base. This orientation mimics how the molding will sit in the corner when installed.
- Set the Angle: Adjust your miter saw to cut at a 45-degree angle. This is the standard angle for creating 90-degree corners when two pieces meet.
- Make the Cut: Carefully cut the crown molding. This 45-degree cut is your foundational piece, ready for either immediate installation (e.g., for an outside corner) or further shaping for a coped joint.
Creating a Coped Joint from a Miter Cut (for Inside Corners)
As per best practices for inside corners, the initial 45-degree miter cut is just the first step in creating a more resilient coped joint.
- Mark the Cut Line: After making your initial 45-degree miter cut, take a pencil and mark along the front edge of the cut. This pencil line will serve as your guide for the next step, making the profile easier to follow.
- Coping with a Saw: Using a coping saw, carefully remove the wood at a 45-degree angle, precisely following the pencil line you just drew. This process involves carving out the exact profile of the molding's face. The resulting coped end will then fit snugly against the flat face of the adjoining piece of crown molding, creating a seamless joint.
- Benefits of Coping: The coped joint is superior for inside corners because it allows one piece to 'nest' into the profile of the other. This mechanical fit hides minor imperfections in the wall's 90-degree angle and is less prone to gapping over time due to seasonal changes in humidity and temperature.
Mitering for Different Corner Types
While the coped joint is excellent for inside corners, standard miter cuts are typically used for outside corners.
| Corner Type | Cutting Method | Ideal Fit | Durability Against Movement |
|---|---|---|---|
| Inside Corner | Start with a 45-degree miter cut, then cope the profile with a coping saw. | Excellent | High |
| Outside Corner | Use two opposing 45-degree miter cuts that meet to form a 90-degree outside angle. | Good | Moderate |
Practical Tips for Precision Mitering
Achieving perfect crown molding joints requires careful planning and execution.
- Test Cuts are Essential: Always make test cuts on scrap pieces of crown molding before cutting your final pieces. This allows you to verify your miter saw settings, check the accuracy of your angles, and ensure the cuts are perfect for your specific walls, which may not always be perfectly square.
- Understand Spring Angle: Crown molding is designed to sit at a specific "spring angle" between the wall and ceiling. Correctly positioning the molding on your miter saw (as described: "bottom side up") is crucial to ensure the cut angle is correct for how the molding will ultimately be installed.
- Account for Wall Irregularities: Walls are rarely perfectly square. For inside corners, this is where coping shines, as it naturally accommodates minor deviations. For outside corners, you might need to slightly adjust your miter saw angle (e.g., 44 or 46 degrees) to achieve a tight fit.
Safety First
When working with power tools like a miter saw or hand tools like a coping saw, always prioritize safety:
- Wear Safety Glasses: Protect your eyes from flying debris.
- Secure the Material: Ensure the crown molding is firmly held against the miter saw fence or clamped in place to prevent kickback during the cut.
- Keep Hands Clear: Always keep your hands a safe distance from the blade.
