Of all the various electric saws on the market, the common circular saw is probably the simplest. If one doesn't buy an electric drill as their first power tool, it is most likely a circular saw will be. These saws are very useful for cutting both sheet goods like plywood and dimensional lumber for construction. You can pretty much frame an entire house with a circular saw, ignoring all other power tools.
The common size for a circular saw is one using a 7-1/4" blade. However, they range from small cordless saws with a 3-1/2" blade all the way up to units with a 10" blade. As the blade is center-mounted on an arbor, the cutting depth of the blade is a little less than half the diameter of the blade. This means that a 7-1/4" blade diameter will comfortably cut through dimensional lumber for construction, even with the blade angled. But to cut through a 4"x 4" post, a 10" blade is needed.
One of the biggest mistakes most users make with a circular saw is to not set the depth of cut. Instead, they cut everything with the blade fully extended which increases the friction/heat and makes it harder for the saw to cut. This not only burns the wood being cut but also warps the blade as well. Ideally, the blade should only stick through the wood about one-quarter inch.
Types of Circular Saws
Basic Circular Saw
Circular saws have been on the market long enough that there are a considerable number of models to choose from. The simple design allows for a wide range of budget models as well, even budget cordless models (which sounds like a contradiction). The typical circular saw uses a planetary gear between the motor and the arbor.
Worm Drive Saw
There are also worm drive saws, which have the motor mounted at a 90-degree angle to the blade and use a worm gear to transfer the power from the motor to the arbor. These worm drive saws provide much more torque as the gearbox absorbs much of the strain of the cut, preventing it from bogging down the motor. While heavier, the worm drive saws are excellent for use by seasoned professionals.
Corded or Cordless?
The decision between corded and cordless models can be a bit difficult for these tools. Modern battery-operated ones are much more powerful than the earlier models and the Lithium-Ion batteries allow for much more cutting before recharging. Nevertheless, corded models are still more powerful than their cordless cousins.
A lot depends on which is more convenient for you as the user. If you will be using the saw in places where it's difficult to get power routed, a cordless circular saw will provide a definite advantage. However, if you have to do a lot of heavy cutting, the corded models are better.
Details to Consider in the Best Circular Saw
The keys to an effective circular saw are power coupled with a good blade. Even though many circular saws come equipped with carbide-tipped blades, you’re probably going to want to replace the factory-equipped blade if you’re a serious user.
Power
The most important thing to consider when looking at a circular saw is the saw's power. Low power saws can bog down in the wood you're cutting, even when cutting plywood. Bog-downs can be worse with thicker materials such as dimensional lumber.
LED Work Lights and Laser Guides
Some saws now come with LED work lights or lasers for alignment. These aid in cutting straight which is the biggest challenge when using a circular saw, especially when cutting sheet goods. While not a necessity, having one of these could make the difference between choosing one saw over another when two saws are otherwise exactly alike.
Ease of Operation
In addition to making it easier to cut straight with a circular saw, manufacturers have been putting a lot of effort into making them more comfortable to work with. Overmolded rubber handles and lower weight cut operator fatigue to make cutting easier, even when you’ve been working all day long.
The weight of the saw, as well as whether the handle is over-molded with rubber, can affect the level of operator fatigue. The handles of some saws are also more comfortable due to their placement and angle.
Fence
For the best straight cutting in sheet goods, it's best to use a circular saw with a fence. There are a couple of circular saws on the market which come with their own fence; however, they're quite expensive. Another option is to buy a fence that clamps to the wood and run the saw alongside it. This option is much cheaper and can provide the same benefit as having a built-in fence on the circular saw.