It takes more than a rusty old circular saw blade and an electric outlet to get straight, clean cuts from your portable circular saw. By keeping your blade sharp and clean, following good safety practices and employing a few tips and tricks of the trade, you’ll be making nice straight cuts faster than you can say “Bob Vila.”
How to Make a Plunge Cut
Most cuts start at one edge of a board or panel and go all the way to the other edge. A plunge cut, also called a stopped cut, starts (and usually ends) in the middle of the workpiece. Plunge cuts are also commonly used to cut into flooring, say, to add a heating register. To make a plunge cut safely, start by resting the front edge of the saw’s base on the workpiece, as shown in the animation. Then, line up the saw blade with the cut line. Raise the blade guard, start the saw and slowly lower the back of the saw base so that the blade plunges straight down into the wood. Once the base is flat on the surface, proceed with the cut. To avoid sawing beyond the corner of a cutout, allow the blade to stop, lift the saw, and finish off the cut with a jigsaw or handsaw.
Getting a Straight Cut on Plywood
A circular saw (check out Amazon’s choice for under $100) is ideal for making long, straight cuts across a big sheet of plywood or particleboard. Even if you own a table saw, using a circular saw to cut a full sheet into lighter, more manageable pieces will save you some back strain.
For a straighter cut than you’re likely to get by eyeballing the saw’s path along a pencil line, guide the saw by running the edge of the saw base against a straightedge clamped to the panel. You can use a long, straight board, a metal straightedge, or an aluminum carpenter’s level as a saw guide. One way to make a long, straight guide is to cut the “factory” edge off a new sheet of plywood or particleboard.
You can temporarily attach your saw guide to the panel with any old clamp, but fumbling with C-clamps can be tiresome. Try one of the new quick-action clamps—they’re fast, they have padded jaws that won’t damage the work, and they can be tightened with one hand.
Since the guide must be offset to the line of cut by the distance between the edge of the saw’s base and the saw blade, you can save time and trouble by making an offset template, a piece of plywood or stiff cardboard that’s the same dimension as the offset. By setting one edge of your offset template on the line of cut and butting the saw guide against the other edge, your saw blade will cut right along the line without you having to measure each time.
Making Easy Square Crosscuts
You can get square crosscuts by clamping a guide onto the lumber you’re cutting, but it takes a lot of fiddling around. Far quicker and more effective is using a speed square, a modern variation of a framing square. Butt the square’s raised edge against the edge of the lumber and hold the speed square in place with one hand while you make the cut with the other. The edge of the saw base slides along the square’s other edge.
To prevent the saw blade from cutting anything it’s not supposed to, don’t set the depth of the blade any deeper than necessary. Extending the blade below the thickness of the work by the length of a saw blade tooth is about right. This setting keeps the blade from cutting too deeply into sawhorses or stock supports, and it keeps injuries to a minimum.
There are times when you’ll want to hold back the guard to prevent it from jamming against the work, such as when making a bevel cut. Hold the guard’s lever until the cut is underway. As tempting as it may be, however, never tie back your circular saw’s spring-loaded blade guard. It’s there to protect you and keep your fingers attached to your hand.
When you’re working outdoors with a corded circular saw or any other power tool, protect yourself from shock by plugging your extension cord into a GFCI receptacle. And always make sure your extension cord is rated to handle the amperage of your power tool.
Keep the base of your circular saw free of dirt and pitch buildup so it can slide smoothly over rough surfaces. To help the base glide more easily, treat it occasionally with car wax or a spray-on dry lubricant. One caveat: If you plan to finish wood you’re cutting with a varnish, lacquer or other clear finish, avoid using spray lubricants that contain silicone, as it can leave a residue that will affect the finish.