How to Cut Plywood With a Circular Saw

To cut plywood straight with a circular saw, support the whole sheet, clamp a straightedge as a guide, use a fine-tooth blade set just below the board, and cut with the good face down. The steps below give clean, square cuts without a table saw. For the other saws and what each one is for, see types of saws.

What you need

• A circular saw with a sharp 40–60 tooth carbide blade
• A straightedge guide: a factory edge of plywood, an aluminium level or a track
• Clamps
• Support: a sheet of rigid foam on the floor, or sawhorses with two long boards
• Tape measure, square, pencil and masking tape

1. Plan your cuts first

Before touching the saw, lay out every part on the sheet. Break large sheets down into strips first, along the length, then cross-cut the strips into parts. Keep the visible parts with the grain running the right way. A cut list optimizer does this in a minute and shows the order of cuts.

2. Support both sides of the cut

The most common cause of a bad cut is a sheet that sags and pinches the blade. Lay the sheet on a piece of rigid foam insulation on the floor and cut right through into the foam: both pieces stay supported. On sawhorses, place supports on both sides of the cut line.

3. Good face down

A circular saw blade spins upward through the board, so it tears fibres on the top face. Put the face that will show down. For extra protection, score the line with a utility knife or cover it with masking tape.

4. Set the blade depth

Set the blade 3–6 mm (1/8–1/4 in) deeper than the plywood. More teeth are in the cut at once, the cut is cleaner, and less blade is exposed.

5. Clamp a straightedge

Measure the distance from the edge of the saw base to the blade (the offset). Mark your cut line, then clamp the straightedge parallel to it at the offset distance, on the side of the part you keep. Remember the kerf: the blade must run on the waste side of your line.

6. Make the cut

Start the saw before it touches the board, keep the base pressed against the guide, and push at a steady speed without forcing. Let the saw stop before lifting it.

7. Check and trim

Check the part with a square. If the factory edge was damaged, trim 5–10 mm from it first; most layouts include this edge trim.

Cutting melamine and MDF without chipping

Melamine chips along the cut because the blade tears the hard coating as its teeth leave the board. Three things stop it: a sharp 60-tooth (or finer) blade with a triple-chip or high-angle grind, the good face down under a circular saw, and a scored line. Score through the coating with a sharp knife against the straightedge, or run the saw first at about 2 mm (1/16 in) deep and then cut through. Masking tape over the line also helps. MDF does not chip, but it makes very fine dust: wear a dust mask and cut outdoors or with a vacuum attached.

Using a circular saw safely

• Keep both hands on the saw and the cord behind you; never reach under the board.
• Let the blade reach full speed before it touches the wood, and let it stop before you lift it.
• Support the board on both sides of the cut so the kerf does not close and pinch the blade: a pinched blade kicks the saw back.
• Stand to the side of the saw, not behind it, and wear eye and hearing protection.
• Check that the lower guard springs back before you set the saw down.

Common mistakes

• Cutting with the good face up and getting splinters.
• Letting an offcut fall at the end of the cut and tear the corner: support it.
• Forgetting the kerf, so the last part in a strip is short.