What a miter saw does
A miter saw is a circular blade mounted on a pivoting arm above a fixed table and fence. You hold the material against the fence, lower the spinning blade through it and release the trigger when the cut is done. Because the blade swings left or right and often tilts, one saw can make crosscuts, miters and bevels with good repeatability. It is a crosscutting machine, not a tool for ripping boards along their length.
Miter and bevel in plain terms
- A miter cut is an angled cut across the width of the board, made by rotating the table. The classic example is two 45-degree cuts meeting to form a 90-degree outside corner.
- A bevel cut tilts the blade so the cut slants through the thickness of the board.
- A compound cut combines both, as in crown molding, where the board lies at an angle to the fence and both settings are used together.
When you set angles, remember that the number on the saw is the angle of the blade relative to the fence, not the angle of the corner you are building. Two matching cuts at half of the corner angle make that corner when the walls are square. Rooms are often not perfectly square, so test fit on scrap. The reason joints open up is covered in the discussion of miter joints.
Setup and safety
Before a cut:
- Read the manual, especially the sections on guards and blade changes.
- Unplug the saw or remove the battery before changing the blade or adjusting anything.
- Wear safety glasses and hearing protection. Dust protection is advised for most materials.
- Check the blade for sharpness, damage and correct installation, with the arbor nut tight.
- Make sure the guard moves freely and returns.
- Secure the saw to a stable stand or bench, and give long boards supports at the same height as the saw table on both sides.
Long boards that hang unsupported can tip, shift or bind, so extend the support instead of holding the overhang with one hand.
Hands and body position
The biggest hazard is hands entering the blade path. Develop these habits:
- Draw a mental no-hand zone on both sides of the blade, as the manual describes, and keep hands outside it.
- Hold the stock against the fence with your hand well away from the blade. Use a clamp if the piece is short or small.
- Do not cross your arms over the blade path or hold the offcut near the blade.
- Do not reach around the blade to remove scraps until it has stopped completely.
- Keep your face and body out of line with the blade.
- Never cut freehand, without the fence for support.
Let the blade reach full speed before lowering it, move through the cut at a steady rate, and keep the arm down until the blade has stopped spinning after you release the trigger.
Very short pieces are risky because they cannot be held away from the blade. Cut them from longer stock instead and then trim to length.
Clamping the work
Many saws come with a built-in clamp or accept an accessory one. Clamp the board against the fence and the table, keeping the clamp outside the blade path and checking its clearance with the arm up and with the blade down. Clamping prevents creep, which is the slight sideways shift that spoils angles. It also frees your hand.
Stop blocks for repeat cuts
When you need several pieces the same length, do not mark and align each one. Clamp a stop block to the fence or an extension at the desired distance from the blade, then butt each board against it. All the pieces end up identical, with less measurement error.
Place the block so the cut-off piece is not trapped between the block and the blade, where it can be thrown. A block on the fence well ahead of the blade, or one that leaves clearance for the offcut, avoids this. A story stick can also help you transfer the length repeatably.
Checking accuracy
Miter saws can drift out of adjustment, especially after transport.
- Check the 90-degree setting. Cut a piece of flat stock, flip one half over and put the two cut edges together against a straightedge. If they do not meet tightly, the blade is not square to the fence. Alternatively, check with a reliable square, using the checking square approach.
- Check the bevel stop. Do the same test with the blade tilted to zero.
- Verify the common detents, such as 45 degrees, using a dependable angle gauge or by cutting test joints.
- Look for blade runout. A wobbling blade gives rough, uneven cuts.
Your manual shows how to adjust the saw. Slightly different test cuts expose errors that are hard to see by eye, because the error doubles when two cuts meet.
Getting clean cuts
- Use a sharp blade with a tooth count suited to the material. Higher tooth counts generally produce smoother cuts in trim and molding.
- Place the good face according to where splinters will occur.
- Support the cut line close to the blade, and keep the board flat against the table.
- Cut slowly through the finish, and release the trigger at the bottom of the stroke, waiting for the blade to stop before lifting.
- Cut just outside the mark and sneak up on the fit if the joint is critical.
Remember the blade removes a thin strip, as shown by saw kerf. Decide which side of the line the kerf falls on.
Dust
Miter saws throw dust and chips. A dust bag helps only partly, and a connection to a shop vacuum can capture more. Use a mask, and clear the area regularly.
This is general information, so follow the instructions for your saw. When you are unsure about an unfamiliar cut, practice on scrap first.