Circular Saw Tips: Cutting Plywood
by Joseph Truini
The circular saw is arguably the most versatile and indispensable woodcutting tool ever produced. Its combination of power, speed, depth-of-cut capacity and portability makes it a favorite tool with homebuilders, woodworkers and DIYers.
Circular saws can be used to make square, miter, bevel and compound-angle cuts. When fitted with the appropriate blade, it can even cut metal and concrete. However, there's one job for which the circular saw is particularly well-suited: cutting large sheets of plywood down to size.
To help you make the cleanest, safest, most accurate cuts, I've listed six time-proven tips and techniques for cutting plywood with a circular saw. Just remember to always wear eye protection and a dust mask when using any power tool.
Splinter-Free Cutting - two techniques
The spinning blade of a circular saw enters the bottom of the board you're cutting and exits through the top. As a result, when cutting plywood, splintering often occurs on the top surface. Now that's not a concern when cutting wall or roof sheathing, but it's important to avoid splintering when sawing finer grades of plywood, including expensive hardwood-veneer plywood.
Method 1: To prevent splintering on side of the plywood, all you need to do is place the plywood sheet with its best side facing down. That way, any splintering will occur on the top surface, which is the backside of the sheet.
Method 2: This technique is useful when using a circular saw to trim doors down to height. Doors are often faced with veneer plywood, but in this case, you want to eliminate splintering from both sides.
To do so, place the best side (meaning the side of the door that will be most visible once it's hung) face down. Then score along the edge of the cut line with a sharp utility knife. Now when you make the cut, the wood fibers will break off cleanly at the scored line, leaving a smooth, splinter-free cut.
When you're cutting plywood—and other sheet goods—it's important to provide proper support to eliminate dangerous kickback. Kickback occurs when the plywood bends or sags slightly and the blade gets pinched in the kerf. The saw can then suddenly kick back toward the user—with its blade spinning at full speed.
To avoid kickback, lay four long 2x4s underneath the sheet you're cutting. Place one 2x4 near each outer edge of the sheet. Take each of the remaining two 2x4s and set one on either side of the cut line. Then, when you make the cut, each half of the plywood sheet will be fully supported by two 2x4s throughout the entire cut.
Making Precise Rips
A rip cut is simply a cut that runs parallel with the grain of the wood, as opposed to a crosscut, which goes across the wood grain. Most circular saws come with a metal rip guide that attaches to the saw's baseplate. This type of guide works okay, but it's limited to rips of only about six inches wide. A better option is to clamp an 8-foot-long board in place for use as a straightedge guide.
You could make the guide from a perfectly straight 1x8 or 1x10, but I prefer a 10- to 12-inch-wide wide rip of ½-inch birch plywood. The factory edge of the plywood is always smooth and perfectly straight, making it an ideal saw guide.
Set up the straightedge guide by first marking the cut line onto the plywood. Next, with the saw unplugged, measure the distance from the saw blade to the edge of the saw's baseplate, which let's say, is 3½ inches. Now measure 3½ inches over from the cut line and clamp or screw the straightedge guide in place. Plug in the saw and make a perfectly straight cut by steering the saw along the edge of the plywood guide.
When you need to cut more than one piece of plywood to the same size, try a technique known as gang cutting. Stack four or five plywood sheets on top of each other. Be sure the edges of the sheets are perfectly aligned, and then securely clamp them together. Adjust the saw blade to its maximum depth of cut and saw through all the sheets at the same time.
When gang cutting, it's important to use a sharp blade and to advance the saw with slow, steady pressure. Don't push too hard or you'll risk overloading and damaging the saw's motor.
When plunge cutting, keep the nose of the baseplate pressed against the plywood,
then slowly lower the spinning blade to make the cut.
A circular saw is ideal for plunge cutting a hole into the middle of a plywood sheet. However, this is a potentially dangerous technique if not done properly.
Start by marking the outline of the square or rectangular hole onto the plywood sheet. Next, lift the rear of the saw, but keep its front edge pressed firmly down on the sheet. Raise the lower blade guard out of the way, while keeping a firm grip on the saw. Now, squeeze the trigger and slowly lower the blade into the wood. Don't advance the saw forward until its entire baseplate is sitting flat on the plywood surface. Once the baseplate is in place, push forward to cut up to the corner of the hole.
Release the trigger and wait for the blade to come to a complete stop before lifting the saw out of the kerf. Repeat the previous steps to make the final three plunge cuts to form the hole.
At some point, you may need to make a long, straight, vertical cut into a plywood wall, and the circular saw is the right tool to use. Just remember to start the saw at the top of the wall and cut down. That way, gravity will be working in your favor; simply allow the weight of the saw to advance the blade through the cut.
About the author: Home improvement expert Joe Truini is the author of many do-it-yourself books, and writes on home improvement and DIY for The Home Depot. Joe also has many years of hands-on construction carpentry experience. For more information on plywood and lumber options, visit the Home Depot website.