Compound miter saw

What Is a Compound Miter Saw?

A compound miter saw is a stationary power tool designed to make precise angled cuts in wood and similar materials. It has a circular blade mounted on a hinged arm that swings down to cut the workpiece. Two key adjustments make it special: the table rotates left or right for a miter angle, and the saw head tilts for a bevel angle. Used together, you can cut complex compound angles in one pass—ideal for crown molding, picture frames, and any trim that meets at a corner.

Unlike a basic chop saw (straight cuts only), a compound miter saw handles angled joints accurately and quickly, with built-in detents (preset stops) at common angles such as 45° and 22.5°. Many models also collect dust, have depth stops for cutting grooves, and include lights or lasers to show the cut line.

How It Works

• Miter adjustment: Rotate the saw table left or right to cut across the face of a board at an angle. This is how you cut the corners of a picture frame.
• Bevel adjustment: Tilt the saw head to angle the blade relative to the board’s thickness. This helps when cutting crown molding “flat” or creating angled edges.
• Compound cut: Use both adjustments at the same time for a single pass that produces an angled face and an angled edge.

Most saws have a rear fence to support the workpiece, a clamp to hold it steady, and a trigger handle to lower the blade through the material. Sliding models add rails that let the head move forward and back, increasing the crosscut capacity for wider boards.

Common DIY Uses

• Trim work: Baseboards, casing, chair rail, and crown molding.
• Framing projects: Picture frames, mirror frames, and decorative boxes.
• Flooring and decking: Cutting end joints, transitions, and stair trim.
• Built-ins and shelving: Face frames, aprons, and precise cut-to-length parts.
• PVC and composites: Window trim, lattice, and non-structural outdoor pieces (with an appropriate blade).

Tip: For fine trim, use a high-tooth-count blade (60–80 teeth on a 10-inch saw) to reduce tear-out and produce smooth edges.

Types and Variations

• Single-bevel vs. dual-bevel:
  • Single-bevel saws tilt to one side only. You may need to flip the workpiece for mirror-image cuts.
  • Dual-bevel saws tilt left and right, making repeated opposing cuts faster and reducing handling of long trim.
• Non-sliding vs. sliding:
  • Non-sliding saws are compact and great for small shops or trim. They excel at accuracy but have limited crosscut width.
  • Sliding saws ride on rails, allowing you to cut wider boards (useful for shelves and deck boards).
• Blade sizes: Common sizes are 7-1/4, 8-1/2, 10, and 12 inches. Larger blades cut wider and thicker stock but are heavier and cost more. Many homeowners find 10 inches a practical balance.
• Corded vs. cordless: Corded models offer continuous power. Cordless saws add portability and are handy on jobsites or small spaces—just keep spare batteries charged.
• Cut-line guides: Lasers draw a line on the workpiece, while shadow-line lights cast the exact blade shadow for more accurate alignment.

How to Choose the Right Saw

• Project fit: For primarily trim and picture frames, a non-sliding 10-inch single- or dual-bevel saw works well. If you plan to cut shelves, deck boards, or wide casing, consider a sliding model.
• Capacity: Check the maximum crosscut width and vertical crown/base capacity (both “nested” against the fence and flat on the table).
• Accuracy features: Look for positive miter detents, a sturdy fence, tight rail tolerances on sliders, and easy-to-read scales.
• Dust collection: A rear dust port that connects to a shop vac greatly reduces mess and improves visibility.
• Ergonomics and footprint: Verify the saw fits your workspace and that the handle, bevel lock, and miter release are comfortable for you.
• Blades: Plan on buying a fine-finish blade for trim and a general-purpose blade for framing or rough cuts. Match the blade to your material (wood, MDF, PVC, or non-ferrous metals like aluminum with the proper blade). Avoid cutting steel—use a metal chop saw for that job.

Setup, Safety, and Cutting Tips

• Stable support: Place the saw on a firm bench or stand. Add outfeed supports or extension wings for long boards to prevent tip-down.
• Mark clearly: Mark the waste side and align the kerf (blade thickness) to your layout line. Use a square to transfer lines to face and edge for reference.
• Secure the work: Keep the board flat against the table and tight to the fence. Use the built-in clamp or a hold-down when possible.
• Start and finish cleanly: Let the blade reach full speed before cutting. Lower the blade steadily; after finishing the cut, allow it to stop before raising it fully to avoid throwing small offcuts.
• Reduce tear-out: Use a sharp, fine-tooth blade. Add a sacrificial backer board against the fence and a zero-clearance insert if available.
• Use stop blocks: For multiple identical pieces, clamp a stop block to your fence or an auxiliary fence. This speeds up repeatable accuracy.
• Crown molding options: Cut crown “nested” against the fence to duplicate its installed angle, or lay it flat and use measured miter and bevel settings (check your molding’s spring angle and use a crown chart or calculator).
• Keep hands clear: Maintain at least 6 inches between your hands and the blade path. Never cross your arms while cutting.
• PPE: Wear safety glasses and hearing protection. Connect dust extraction if possible, or wear a dust mask when cutting MDF.

Maintenance

• Blade care: Keep the blade clean and sharp; pitch buildup reduces cut quality and strains the motor. Replace or sharpen dull blades.
• Calibration: Periodically check and adjust miter, bevel, and fence squareness using a reliable square. Verify detents are accurate.
• Rails and slides: On sliding models, keep rails clean and free of pitch or dust. Follow the manufacturer’s guidance for lubrication if required.
• Dust: Empty bags, clear ports, and vacuum the saw regularly to maintain visibility and accuracy.

Common Mistakes to Avoid

• Lifting the blade with it spinning in the cut: Wait for the blade to stop to prevent pulling fibers or launching offcuts.
• Not supporting long stock: This causes the workpiece to pivot mid-cut, leading to inaccurate angles and binding.
• Forgetting about kerf: The blade removes material. Always cut on the waste side of your line.
• Using the wrong blade: A coarse framing blade will chip MDF and trim. Match tooth count and blade type to the job.
• Skipping test cuts: Always test angles on scrap before cutting finish material.

Related Terms

• Miter saw (basic): A saw that cuts miters without bevel tilt.
• Dual-bevel miter saw: Tilts left and right.
• Chop saw (metal): Similar format but built for cutting metal with abrasive or specialized blades.
• Table saw: Great for ripping boards lengthwise; not a substitute for quick angled crosscuts.
• Track saw: Portable straight-line cutting, mostly for sheet goods.
• Miter box: Manual hand-saw guide for simple miter cuts.

Practical Examples

• Baseboard corners: Set a 45° miter for inside and outside corners. For tight inside joints, cope one piece after a 45° cut.
• Picture frame: Cut four pieces with 45° miters, using a stop block for identical lengths. Glue and clamp.
• Crown molding: Use your saw’s compound settings or nest the crown against the fence; mark the ceiling and wall edges to prevent confusion.
• Decking: On a sliding saw, crosscut composite deck boards to length with a fine-tooth blade, supporting both ends for clean edges.
• Window casing: Use 45° miters for the head and legs, check for square openings, and tune angles by a degree or two if the walls are out of square.