For precision cuts in lumber and other rigid materials, take a circular saw for a spin.
Photo: Oisin Duke, Flickr
A circular saw is used for making straight square or bevel cuts in many common building materials, including lumber, plywood, and masonry. You can use it to cut an opening in your roof to install a skylight, or you can use it to cut shelving for a bookcase. You can even use it, with the appropriate blade, to cut a piece of bluestone to fit a patio or path. The tool has a motor, shaft, circular blade and blade guard, two grips and a flat base upon which the saw rides as you make a cut.
Circular Saw Controls
Besides the trigger-style on-off switch, there are really only two controls:
-- One control is a knob or lever that unlocks to allow the motor and blade assembly to pivot up or down the base. Raise the assembly and the saw's depth of cut is reduced. Lower the assembly and depth of cut is increased.
-- The other control is a knob that, when loosened, allows you to pivot the saw assembly to the side, thereby changing the angle of the blade and allowing you to make bevel cuts at angles that range between 0° and 55° (or slightly more or less).
Using a Circular Saw
To make a cut with a circular saw, make sure your workpiece is well-supported across most of its length. Never try to cut a piece of lumber that's only supported at its ends, as if it were a bridge.
Always mark a cut line on the work piece; you should have a visual reference even for a rough cut (one where the exact measure is not so important).
Set the blade depth so it's slightly deeper than the thickness of the board you intend to cut. This leaves less blade exposed and minimizes the chance for an accident. Then push the saw along the cut line at a steady pace. You'll notice that the rpms slow if you pushing the saw too fast.
When beginning a cut that needs to be accurate, position the blade to the waste side of the cut line. Saw blades, however thin, have a width (kerf). If you cut to the wrong side of the line, or even along the middle of the line, the workpiece will not end up being the dimension you intended.
If the cutoff (section of a board you're removing) is long, have a helper on hand to support it so it doesn't fall and break due to its weight before you complete your cut.
The best way to cut a piece of lumber for a beginner is to support the board you're cutting on a ¾-inch sheet of scrap plywood. (The plywood can rest on a table or on sawhorses.) Clamp the work piece to the plywood so you can use both hands to hold the saw. Set the depth of cut as described above and make the cut. Once you become more familiar with the tool, you will likely move on to holding the work piece with one hand and pushing the saw with the other, but clamping is recommended for safety-especially if you're a little short on arm strength.
Even experienced do-it-yourselfers will find that it's difficult to make long cuts without a guide. There's usually an accessory guide that comes with the saw, but it's of limited use. A better way is to clamp a straightedge to the work piece at the cut line. Then allow the edge of the saw base to ride against it as you make you saw. Just be sure to locate your clamps in places where they won't block the path of the saw.
As you become more experienced, you'll find it's possible to make plunge cuts with a circular saw, too. Plunge cuts, are useful for making cutouts. A good example is when you must cut a hole in sheathing for a window. To make a plunge cut, retract the blade guard, rest the front of the saw base on the work piece surface, turn on the saw, and and lower the blade into the workpiece until the saw base rests on the surface. You may then push the saw forward as when making a normal cut.
Buying a Circular Saw
Circular saws come in all sizes, horsepower, and weights. Buy one that you can easily heft but that's still powerful enough for the jobs you have planned.
Saw sizes are given by blade size. A good all-round saw size is 7-1/4 inch. For power, go with 15-amp motor.
Saw weights range from close to 10 lbs. to 13 lbs. and up. You can get a very powerful saw that weighs in at 10 lbs.
Try adjusting the bevel, depth of cut controls before purchasing the saw. Some saws have convenient built-in stops as 22.5° and 45°.
Look for a shaft lock. It will make replacing blades a lot easier.
Check for good cut line visibility, too. Being able to see where the blade meets the work piece is key to making an accurate cut. Some saws have a built-in LED light that improves visibility.
Before you leave the store with your purchase, buy the correct blade for the job. A 40-tooth combination blade with carbide-tipped teeth is a good all-purpose blade. (Combination means it's designed for making both rip and crosscuts.) An 18- or 24-tooth blade that sometimes comes with a saw performs poorly. For cutting plywood, a 140-tooth blade is a good investment.
Prices for a good saw begin at $100 go up from there. Saws that cost less will generally not stand up to frequent use.
Maintaining a Circular Saw
Circular saws should be cleaned after each use by blowing with compressed air or brushing with an old paintbrush. Change the blade when it begins to become dull. You'll know it's time when your saw cuts generate smoke and burn marks! Follow the manufacturer's recommendations when it comes to changing motor brushes
Circular Saw Safety Precautions
-- Wear safety glasses and hearing protection.
-- Support the work piece to be cut in such a way that to kerf will not close and bind the blade-a situation that can cause the saw to kick back toward you.
-- Adjust the depth of cut so the blade will cuts no deeper than the thickness of the work piece plus ¼ inch.
-- Tighten all knobs or levers so the base is locked firmly to the motor assembly.
-- Move the power cord so it's well away from the path of the blade.
-- Do not allow the blade to touch the work piece until you have turned on the saw.
-- Position yourself so that saw dust and wood chips will not be thrown in your face.
-- Allow the saw blade to come to a complete stop before putting the saw down.
-- Unplug the saw before adjusting for bevel or depth of cut, and before changing the blade.
-- Do not begin a cut if you will have to overextend your reach before you can complete it.