In the early 19th century, a Shaker woman named Tabitha Babbitt reportedly invented the first circular saw by attaching a saw blade to her spinning wheel.

Modern circular saws originated in 1923, when Edmond Michel created the first handheld circular saw and founded the Skilsaw company to market it. That’s why a circular saw is still sometimes referred to as a skill saw. Whatever you call it, if you’re doing carpentry, you’ll need one whether you’re experienced or about to embark on your first project. There is no substitute for a circular saw if table saw isn’t available.

Cordless circular saws have been around since the 1980s. They’re so portable you can even use one to prune tree branches up to two inches in diameter in a pinch. This isn’t recommended, but you get the idea. It’s a handy tool.

What Is a Circular Saw?

Put simply, it’s a handheld power saw with a circular blade that makes straight cuts along the wood grain (rip cuts) or across the grain (crosscuts). You can replace the woodcutting blade with a specialty blade to cut plastic, stone and many other materials.

Modern versions aren’t much different from Michel’s original Skilsaw. They consist of the following components:

• An electric motor, removable blade, a flat base (AKA shoe or foot) and a handle. In the default position, the blade spins perpendicular to the base, but the base can tilt 45 degrees in either direction for making bevel cuts. The base also adjusts regulates the distance the blade extends below it, controlling the depth of the cut. Besides the standard D-shaped handle, some saws have an additional handle for more control.
• A power control trigger and a safety switch. Circular saws operate at one speed, and the direction of the blade — clockwise with respect to the motor — isn’t reversible. You always push the saw into the work; you never pull it.
• A guard that prevents contact with the blade when it isn’t cutting. The guard retracts as you push the saw through the material, and springs back over the blade when the cut is complete.
• A source of electricity, either a power cord or battery. Corded circular saws are more powerful, but cordless ones with 18- or 20-volt batteries come close.

A standard circular saw accommodates a 7-1/4-in. blade and cuts to a maximum depth of 2-1/2-inches. Some compact circular saws accept blades from 3-3/8-in. to 6-1/2-inches.

Larger saws accept blades with a 10-1/4-in. diameter, and specialized beam saws can take blades with a 16-5/16-in. diameter. They’re typically used by roofers, framers and other professional tradespeople.

Types of Circular Saws

Some circular saws incorporate gears to drive the blade. Others are direct-drive. There are three saw designs:

• Worm drive: Worm-drive circular saws are long and heavy and the gears require lubrication. But they’re also powerful and the preferred tools for heavy-duty construction purposes. The original Skilsaws had worm-drive gears. To accommodate them, the motor is placed behind the blade.
• Sidewinder: The sidewinder design circular saw has the motor next to the blade, offering a more compact shape and an easier sight line for the operator. The blade is usually mounted on a direct-drive spindle on the right side of the motor.
• Hypoid: A hypoid circular saw resembles a worm-drive model but employs a different gear structure that doesn’t need lubrication. It’s as powerful as a worm-drive saw and also best suited for heavy construction.

Corded and cordless

The gears allow worm-drive and hypoid saws to develop more power than sidewinders. Worm-drive and hypoids have powerful 15-amp motors that need to be plugged in. Both corded and cordless sidewinder models are available, and the battery on most cordless circular saws mounts behind the motor.

Batteries for most models are compact and long-lasting, but add weight. Some compact cordless saws have a barrel handle rather than the traditional D-shaped one — an ergonomic bonus.

Shopping for a Circular Saw

Before you purchase a circular saw, hold it in the working position with the cord unplugged or the battery removed and check the following:

• How easy is it to hold in the safety switch and operate the trigger? This is easier to do on some saws than others. Keeping that safety switch depressed can be tiring.
• Does the saw feel heavier on one end than the other? Even a heavy saw can be easy to use if it’s balanced, but an unbalanced saw requires extra effort to control.
• Can you easily see the leading edge of the blade? Most saws have a guide marker on the front edge of the base to help you keep the blade on track. But there will be times you need to follow the progress of the blade itself.
• Does the blade guard come with an easy-to-access lever? You’ll need to retract the blade to make some cuts so you want a big, easily accessible lever.
• Are the markings on the depth and angle gauges clear and easy to read? They should be embossed, not simply marked with paint that can wear off.
• Can you easily adjust the angle of the base and the depth of the cut? Look for levers rather than turn screws. They’ll save you time when you’re working.

Quality saws come with two bonus features you’ll probably want. The first is an LED guide light. That will help you keep the saw on track when your shadow blocks your light source. The second, a laser guide, can be useful for ripping lumber and plywood.