Square Cuts With a Saw Guide
If you own a circular saw, you can make accurate, safe cuts on boards and plywood with this inexpensive saw guide that anyone can make. It effectively replaces the need for expensive power tools such as a table saw or radial-arm saw for most DIY needs. You can make saw guides of several sizes to cut different sizes of boards.
Gather Tools and Materials for Saw Guide
To make your saw guide you will need a sheet of 1/2-in. plywood or MDF, wood glue, 3/4-in. screws, a screwdriver, two clamps, a framing square, and a circular saw. You could easily make this saw guide with a 2 ft. by 2 ft. sheet. Although it is not required, you might also want to have some primer and paint to coat the saw guide. Since it will probably last you many years, a painted surface will protect it from moisture damage.
Cut the Pieces for the Saw Guide
The saw guide is composed of three separate pieces: the base, the fence, and a stop. The base provides the surface for your circular saw to move across when making a cut. It also offers room to clamp the base to the piece you will be cutting.
The fence serves to a guide the shoe of the circular saw in a straight line while making a cut, and the stop allows the saw guide to rest against the piece to be cut to ensure a square cut. Rather than buying three separate pieces, cut the fence and stop from sides of a single sheet of MDF, using pieces of tape in the photo to demonstrate where the cuts were made. The finished saw guide in the photos has a 24 in. by 13 in. base, a 24 in. by 3 in. fence and a 13 in. by 2 in. stop. It's a good size for cutting pieces up to about 20 in. wide.
Before making any cuts, take a moment to mark the factory edges. The three existing edges that you can see on the MDF in the photo are commonly referred to as "factory edges," which means that they were cut in the manufacturing process. These edges are almost always as square and straight as possible, so you want to take advantage of that when assembling your saw guide.
Mark the three edges with a pencil. Plan to use the factory edge of your base as the front edge of your guide. On the small strips, use the factory edge of the fence as the side where the saw shoe will make contact, and let the factory edge of the stop be the side that makes contact with the piece you will be cutting.
Align the Pieces of the Saw Guide
The only way to be sure you will make square, straight cuts when using your saw guide is to make sure that the fence and stop are attached in proper alignment. That means that the guiding edge of the fence (the edge that guides the circular saw) and the alignment edge of the stop (the edge that rests against the piece to be cut) are perfectly perpendicular to each other.
The best way to align these pieces is to clamp a framing square to your base, with one edge aligned perfectly with the factory edge. Then you can set the fence and stop alongside the other edge of the square before attaching them to the base.
Assemble the Saw Guide
Attach the fence and the stop to the base of the saw guide with wood glue and screws. Make sure that each piece is lined up properly with a framing square. Spread some glue on both mating surfaces and apply pressure with a couple of clamps for about 30 minutes. After clamping, check the alignment again to make sure you didn't move anything.
Drive a couple of screws through the fence and the stop into the base. This will be easier if you first drill pilot holes a bit smaller in diameter than the screws. Don't worry about drilling holes all the way through both pieces, but make sure the screw does not poke through. Clean up excess glue with a damp paper towel before it has a chance to dry.
Once the glue has dried, you still have one additional job to perform before your saw guide is ready to use. You want to "custom-fit" the guide to your saw by making one careful cut, gliding the shoe of the circular saw along the fence while you cut the base. Once this is done, the guide will be able to make perfect cuts as long as you use the same saw. If you buy a new circular saw, chances are that you will need to make a new saw guide.
Finish the Saw Guide
Apply a finish to the saw guide; fill the screw holes with wood filler, then sand the surface of the saw guide. Apply primer and a coat or two of paint. This step will protect your saw guide from moisture damage and keep it operating as good as new for many years.
How to Use a Saw Guide
Using a saw guide couldn't be easier. Just place a pencil mark at your cut line, clamp the saw guide with the edge set at the mark, then make the cut while letting the shoe of your circular saw glide along the fence.