Using a Circular Saw

You'll probably use a circular saw more than any other tool for deck building. A saw with a 7-1/4-inch blade and a motor that draws 10 to 13 amps is powerful enough to cut effortlessly through 2x stock, even at a 45-degree angle.

Most saws will come equipped with a combination blade for making crosscuts and rip cuts. If yours has a standard steel blade, replace it with a carbide-tipped combination blade. Inexpensive steel blades will be dull after about four hours of heavy cutting. A moderately priced carbide blade will last a long time and make cleaner cuts throughout its life.

You can accomplish many of your cuts (especially framing cuts) freehand, but for more precision support the workpiece solidly and employ jigs or guides for cuts. Supporting the board will minimize dangerous kickback and splintering along the bottom face as the waste falls away. For all cuts, start the saw off the cut and push the blade into the board with a steady forward motion.

Safety first

Cutting lumber, especially pressure-treated stock, calls for protection. Protect your eyes from flying chips and sawdust with safety glasses. If you are sensitive to pressure-treated lumber, use a facemask. When making frequent cuts, wear ear protectors.

Protect yourself from kickback, too. When the teeth on the rear of a circular saw blade catch or the blade binds in the kerf, the saw can kick back out of its cut line, ruining the cut and endangering the carpenter. Here are some ways to avoid kickback:

  • Don't try to change directions midcut. If your saw veers off the cut line, stop cutting, back up, and start again. Don't run the saw as you back it up -- that also causes kickback.
  • Keep your blades clean and sharp. If you have to push hard to make a cut, chances of kickback multiply.
  • Keep your blades clean and sharp. If you have to push hard to make a cut, chances of kickback multiply.
  • Sometimes a knotted or twisted board, or one with twisted grain, can grab the blade suddenly. Be prepared for this.
  • Operate the saw safely. Never wear loose sleeves or other clothing that could get caught in the blade as you cut. Never bring your face close to the blade as you cut. Keep the power cord clear of the blade.

Cutting freehand

Rest the edge of the board on a solid surface and tilt it up 30 to 45 degrees, keeping the saw guide or the blade visible. Line up the blade with your cut line, start the saw, and let gravity pull it down the line. Keep the saw plate flat on the stock as you cut.

Crosscutting with a guide

Clamp a layout square with its heel plate against the edge of the board, positioned to put the saw blade just on the waste side of the cut. Most saw plates are marked with the distance from the edge to the blade. Put the saw plate flat on the board, start the saw, and push it forward.

Cutting miters

Clamp a layout square to the board as a guide. (Experiment to find the right distance away from the cut line.) Retract the blade guard before starting. The saw might work hard in a miter cut -- don't push too hard. Cut the miter before you cut the board to length so you can recut if you make a mistake.

Rip cutting

To make a rip cut, fit the saw with a rip guide. If the cut is not parallel to the edge of a board, either cut it freehand or clamp a long straightedge as a guide. Don't force the saw away from the cut -- the rip guide might flex with it.

Bevel cutting

Bevel cuts will make the saw work harder, so clamp the board firmly to a work surface using a guide set so the blade will cut along the waste side of the line. Set the bevel gauge to the correct angle and check it with a protractor. Start the saw and ease it into the cut with a slow but constant speed.

Cutting long stock

Support the board so the saw won't bind or kick back and to keep the board from splintering as the waste falls away. If the waste side is longer than 2 feet, support the board in four places. That way both sides of the cut will stay put and you can make a straight, neat cut.

Cutting thick stock

Mark the cut on one side of the piece and transfer the mark to the adjoining sides with a square. Position the saw to the waste side of the line and against a layout square. Push the saw through the cut from one end to the other. Turn the stock and cut each adjacent side.

Transfer the cut line to two adjacent sides, and keeping both lines visible, position a reciprocating saw with the saw shoe against the stock. Keep the blade in line with the waste side of the cut and off the wood. Start the saw, and rock it back and forth through the lines.

Squaring the blade

Don't trust the bevel guide on a circular saw; it could be off by several degrees, producing nonsquare cuts. Check the blade angle with a square, and adjust the plate until it's 90 degrees to the blade. Unplug the saw anytime you adjust the saw.

Changing a blade

Unplug the saw and retract the blade guard. Set the teeth of the blade firmly into a piece of scrap or the top of your outside work surface. Make sure the board won't move. Remove the bolt and tilt the blade out. Reverse the procedure to install the blade.

Setting the cutting depth

Set the blade to extend no more than 1/4 inch through the thickness of the stock. Release the saw plate latch to position the plate to the proper depth.

Good side down

A circular saw blade exits the cut upward and will splinter the top of the board. Where appearance matters, cut with the good side of the board down.


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