Yes, you can cut crown moulding with a compound miter saw. This tool is the best way to get accurate cuts for interior and exterior corners, which is key for beautiful crown moulding installation. Using the right settings makes a big difference.
Setting Up Your Compound Miter Saw for Crown Moulding
Getting your saw ready is the first big step. If you do this right, the rest is much easier. Crown moulding sits at an angle against the saw, unlike flat trim. This resting position changes how you use the miter and bevel settings.
Understanding Moulding Profiles and Spring Angles
Crown moulding is not flat. It has a “spring angle.” This is the angle where the moulding naturally rests against the wall and the ceiling. Most standard crown moulding has a 38-degree or 45-degree spring angle.
- Why this matters: If you set your saw based on a flat board, your corners will look wrong when fitted to the wall and ceiling. You must account for the spring angle.
The Two Main Ways to Cut Crown Moulding
There are two primary ways to place moulding on the miter saw base:
- Coping/Coping Style (Lying Flat): You lay the moulding flat on the saw table. This is easier for beginners but requires more complex angle settings.
- Positioned/Stacked Style (Against the Fence): You stand the moulding up vertically, nesting it against the saw fence and the table, mimicking how it sits in the room. This method often uses simpler angle settings but requires careful clamping or holding.
For the best results and easier math, many pros recommend the Positioned/Stacked Style. This means you are cutting the moulding as if it is already installed.
Determining the Correct Compound Miter Saw Crown Molding Settings
The settings you use depend heavily on how you orient the moulding on the saw table. Let’s focus on the Positioned/Stacked Style as it uses repeatable settings derived from the spring angle.
If your moulding has a standard 38-degree spring angle:
| Angle Type | Setting | Value |
|---|---|---|
| Miter Angle | Rotation along the table | 33.86 degrees |
| Bevel Angle | Tilt of the blade | 31.63 degrees |
If your moulding has a 45-degree spring angle:
| Angle Type | Setting | Value |
|---|---|---|
| Miter Angle | Rotation along the table | 35.26 degrees |
| Bevel Angle | Tilt of the blade | 35.26 degrees |
Important Note: These numbers are derived using specific geometric formulas that compensate for the spring angle. They are often found in a crown molding cutting chart for miter saw reference guide. If your saw allows you to store custom angles, save these settings!
Setting Up Miter Saw for Crown Molding: Precision Check
Before making any cuts, always check your settings with a test piece.
Confirming Miter Saw Bevel Settings for Crown Molding
To verify your bevel angle, especially if you are using a saw without pre-set “crown moulding mode” buttons:
- Set your miter to zero.
- If you are cutting a standard 38-degree spring angle, set the bevel to 31.6 degrees.
- Place a scrap piece of moulding in the stacked position.
- Cut a piece.
- Take a spare piece of moulding, cut a 90-degree corner (or 45/45 if it is a flat piece).
- Test fit the two pieces together. They should form a perfect 90-degree corner against a flat surface (like a wall or a straight edge). If they don’t meet perfectly, adjust the bevel slightly.
Using a Crown Molding Jig for Miter Saw
For frequent crown cutting, a crown molding jig for miter saw is a lifesaver. This simple device usually consists of two small pieces of wood clamped to the saw table. They hold the moulding securely in the required vertical position against the fence and table.
- Benefit: A jig ensures the moulding stays locked in the stacked position for every cut. This removes human error from inconsistent placement.
Cutting Crown Molding Inside Corner with Miter Saw
Inside corners are where two walls meet inside a room (like the corner of a typical hallway). These corners are usually 90 degrees. For a perfect fit, you need two opposite, mirrored cuts.
The 45-Degree Rule vs. Compound Angles
When cutting baseboard, you simply use a 45-degree miter cut on both pieces to make a 90-degree corner. With crown moulding in the stacked position, the simple 45-degree rule fails because of the spring angle. You must use the compound settings derived above.
Steps for the Inside Corner (38-Degree Spring Angle Example)
Assume you are cutting the piece that goes on the left wall (Piece A) and the piece that goes on the right wall (Piece B).
- Set the Saw: Use the compound settings: Miter 33.86°, Bevel 31.63°.
- Cutting Piece A (Left Wall):
- Orient the moulding so the top edge faces the ceiling side of the saw and the bottom edge faces the saw table.
- Place the long, pointy end of the cut toward the left side of the saw (if looking from behind the saw). This creates a left-hand return cut.
- Cutting Piece B (Right Wall):
- You must mirror the setting for the second piece.
- Keep the Bevel at 31.63°.
- Change the Miter to the opposite direction: 33.86° in the opposite direction. (If Piece A was cut at +33.86°, Piece B must be cut at -33.86°).
- Ensure the orientation of the moulding matches Piece A (top/bottom placement) so the resulting profile matches when fitted together.
When fitted, the two pieces should slide together snugly to form a tight 90-degree angle against a flat surface.
Cutting Crown Molding Outside Corner with Miter Saw
Outside corners jut out from the wall (like the corner of a bay window or an exterior wall). These also require two mirrored cuts that meet at 90 degrees.
The Reverse Compound Settings
The cuts for outside corners are essentially the reverse of the inside corner cuts. You are still joining two pieces at 90 degrees, but the angle of the moulding relative to the room means you use opposite bevel settings relative to the miter setting.
Steps for the Outside Corner (38-Degree Spring Angle Example)
- Set the Saw: Use the compound settings: Miter 33.86°, Bevel 31.63°.
- Cutting Piece A (Left Wall):
- Orient the moulding the same way you did for the inside corner (top edge up, bottom edge down).
- For the outside corner, the angle points outward. You will typically make the cut so the finished edge slopes toward the room.
- Cutting Piece B (Right Wall):
- You need the mirror image. Keep the Bevel at 31.63°.
- Set the Miter to the opposite direction: 33.86° in the opposite direction.
When you assemble these pieces, the angled profiles should meet cleanly at the outside point. If they look too blunt or too sharp, re-check the spring angle specification for your specific moulding.
Deciphering the Compound Angle Chart for Crown Molding
If you are working with varied spring angles or need to confirm settings quickly, a comprehensive chart is invaluable. This section explains how these charts are built, which helps you troubleshoot if your saw settings don’t match standard charts.
The core math involves finding the difference between the wall angle (usually 90°) and the moulding’s spring angle.
The basic relationship for any standard miter/bevel combination is:
$$Miter\ Setting = 45° – \frac{Spring\ Angle}{2}$$
$$Bevel\ Setting = \arctan\left(\frac{\sin(Spring\ Angle) \times \tan(Miter\ Setting)}{\cos(45° – Miter\ Setting)}\right)$$
This math is complex, which is why pre-calculated charts are so useful.
Example Crown Molding Cutting Chart for Miter Saw (Positioned/Stacked)
This table shows standard angles for common spring angles.
| Spring Angle | Inside Corner Miter | Inside Corner Bevel | Outside Corner Miter | Outside Corner Bevel |
|---|---|---|---|---|
| 38 Degrees | 33.86° | 31.63° | 33.86° | 31.63° |
| 45 Degrees | 35.26° | 35.26° | 35.26° | 35.26° |
| 52 Degrees | 36.29° | 32.66° | 36.29° | 32.66° |
Note on Corner Cuts: For inside and outside 90-degree corners, the miter and bevel degrees are the same, but you must cut them in opposite directions (mirror images).
How to Miter Crown Molding on a Saw: The Flat Lay Method (Coping Style)
Some installers prefer to lay the moulding flat on the saw table, just as they would a baseboard. This is called “lying flat.” This method requires much larger miter angles but uses a zero-degree bevel.
Why Use the Flat Lay Method?
- Familiarity: If you are good at cutting baseboards, this feels more intuitive.
- Simpler Saw Setup: The blade stays tilted at 0 degrees (no bevel adjustment needed).
Required Settings for Flat Lay (38-Degree Spring Angle)
When laid flat, the blade needs to be set to achieve the correct angle across the moulding’s width.
- Miter Angle: 48.87 degrees (for 38° spring angle)
- Bevel Angle: 0 degrees
This calculation results in a very wide miter angle. It works, but often requires a larger miter saw capacity, and the resulting cuts are very shallow on the moulding’s face, which can sometimes chip easily.
Scarf Joint Crown Molding Miter Saw Technique
What if the wall run is longer than a single piece of moulding? You need to join two pieces seamlessly. This joint is called a scarf joint. A perfectly executed scarf joint is almost invisible.
A scarf joint is not a 90-degree corner joint. It’s a long, shallow cut used to join two pieces end-to-end along a straight wall.
Preparing for a Scarf Joint
- Angle Selection: For the best, least noticeable joint, use a shallow angle, typically between 12 and 18 degrees. A 15-degree cut is a good starting point.
- The Setup: Set your miter saw to your chosen angle (e.g., 15 degrees) and keep the bevel at 0 degrees (if cutting flat) or use the required compound angle if cutting stacked.
- The Join:
- Cut the first piece with the angle sloping up and toward the direction of the join.
- Cut the second piece with the angle sloping up and away from the direction of the join.
- This creates two angled surfaces that mate perfectly, spreading any slight inconsistency over a longer length.
Tip: Apply a small amount of wood glue to both mating surfaces before pressing them together. Clamp them securely. Once dry, the joint should be nearly invisible, provided your angle was precise.
Advanced Techniques and Troubleshooting
Even with the right settings, installation quirks can cause problems.
Dealing with Non-90 Degree Corners
Rarely are room corners exactly 90 degrees. They might be 88 degrees or 92 degrees. If you use standard 45-degree cuts (or standard compound cuts) on these walls, the top or bottom of the moulding will have a gap.
How to Adjust:
- Measure the Actual Corner Angle: Use a reliable digital angle finder or a sliding T-bevel to measure the actual angle between the two walls. Let’s say the corner is 88 degrees.
- Calculate the Miter Adjustment: Divide the actual angle by two to find the necessary miter setting: $88° / 2 = 44°$.
- Apply to Compound Settings: If you are using the stacked method for a 38° spring angle, you would replace the standard miter setting (33.86°) with your calculated 44°, keeping the bevel angle the same (31.63°).
This ensures the piece fits the wall angle perfectly, even if the room geometry is imperfect.
Can I Cut Crown Moulding Without a Compound Miter Saw?
While technically possible, it is extremely difficult and often results in poor fits.
- Using a Standard Miter Saw: You can only use the flat lay method. You would need to figure out the correct 45-degree offset needed to compensate for the spring angle and add that to your 45-degree cut. This usually requires complex trigonometry or looking up charts specifically for flat lay mounting.
- Coping: For inside corners, many pros revert to coping the moulding instead of cutting a compound inside corner. Coping involves cutting the standard 45-degree miter, and then using a coping saw to cut away the waste material on the profile itself so it fits snugly over the profile of the other piece. This technique bypasses the need for precise compound bevel settings entirely for inside corners. Outside corners, however, still often require a precise compound cut or a coping mechanism designed for outside angles.
Maintaining Your Saw for Clean Cuts
A dull blade or a loose saw will ruin even the best compound miter saw crown molding settings.
Blade Quality is King
Crown moulding is often soft pine or MDF, but it can also be hard woods.
- Tooth Count: Use a high-tooth-count blade, ideally 60 to 80 teeth (TPI). More teeth mean a smoother cut and less tear-out on the profile face.
- Blade Condition: Dull blades generate heat, which can melt MDF dust into a sticky residue, leading to rough edges. Change blades often, especially when cutting intricate profiles.
Keeping the Saw Fence True
When using the stacked/positioned method, the fence is crucial. It acts as the “wall,” and the table acts as the “ceiling.”
- Ensure the fence is perfectly perpendicular (90 degrees) to the saw table when the saw is set to zero miter.
- If the fence is slightly off, all your compound angle cuts will be incorrect by that small margin. Use a machinist square to check this periodically.
FAQ Section
What is the spring angle of crown moulding?
The spring angle is the specific angle at which the crown moulding rests against the wall and the ceiling when it is installed in the room. Standard angles are 38 degrees or 45 degrees.
Do I always need to use bevel settings for crown moulding?
Yes, if you are cutting the moulding in the “stacked” or “positioned” style, which is highly recommended for precision. The bevel setting tilts the blade to account for the moulding’s spring angle so the top and bottom edges sit flush when installed.
What is the easiest way to cut an inside corner?
The easiest method, if you are comfortable with it, is coping the moulding rather than cutting a compound inside corner. For compound cutting, use the established miter and bevel settings for your specific spring angle.
How do I prevent gaps when joining two pieces of crown moulding on a straight run?
Use a shallow, precisely cut scarf joint (usually 12 to 18 degrees). Glue and clamp the joint tightly while the glue dries.
Can I just use 45-degree miter settings for crown moulding?
No, not unless you are laying the moulding completely flat and your moulding has a 45-degree spring angle (which is uncommon for standard installations). For standard stacked installations, simple 45-degree miter cuts will result in visible gaps at the top or bottom edge of the joint.