The circular saw was invented in England at the turn of the nineteenth century, though there is considerable disagreement on precisely when and by whom the tool was devised. Whenever and wherever it happened, the innovation was a great step forward. Among many advantages of the circular saw is its simple efficiency. Unlike the reciprocating saw, which cuts only half the time (each cut-ting stroke is followed by a return stroke), the circular saw is ready to cut whenever its blade is in motion.
With the possible exception of the electric drill, the hand-held cir-cular saw is the power tool most often found in the average homeowner's tool chest. It is easy to use, affordable, and astonishingly flexible and practical. The portable circular saw has other names, too, including the Skilsaw (a proprietary trade name) and electric handsaw.
The portable circular saw is designed to cut lumber and boards to size. Various models require different-sized blades, among them blade diameters of six and a half inches and eight and a quarter in-ches; the most popular by far, however, are the seven-and-a-quarter- inch models.
Most portable circular saws have electric motors with two or more horsepower that turn the blade at about five thousand revolutions per minute; capacities and revolutions per minute vary from model to model. The motor is protected in a housing, the blade by a fixed guard on top and a retractable guard below. There is a handle on top, and a sole plate or shoe on the bottom. Some models come with an adjustable T-guide.
A typical circular saw weighs between nine and twelve pounds. Most contemporary models feature insulated, rigid plastic casings, with steel soles and guards.
The vertical angle of cut can be adjusted from its standard ninety degrees to forty-five degrees, or to any angle in between. The depth of cut can be adjusted, too. A typical seven-and-a-quarter-inch cir-cular saw will cut to a depth of two-and-a-quarter inches at 90 degrees. At a forty-five-degree angle, the saw will cut through a two- by-four on one pass, a thickness of one and a half inches.
These saws can also be fitted with masonry or other specialty blades for cutting other materials. Blades with a wide range of teeth configurations for cutting wood are also available, though a com-bination blade, which crosscuts and rips, may suffice for most or all of your needs.
In addition to the common seven-and-a-quarter-inch saw, other sizes are available. On one extreme, there's a three-and-three- eighths-inch saw that uses a rechargeable battery. This saw is expen-sive, however, and has significant built-in limitations. For example, its depth of cut is only eleven-sixteenths of an inch when sawing a forty-five-degree bevel. And the saw runs out of power pretty quickly (ripping four lengths of half-inch plywood is the present maximum per charge). For some applications, however, the convenience and light weight of this little saw may make it very handy. At the other end of the spectrum, there are giant models designed to be used by tim-ber framers, but they are unwieldy and of little use to most wood-workers.
One heavy-duty variety of the portable circular saw is the worm-drive saw. Most circular saws are direct-drive, meaning that the shaft to which the blade is attached is part of the electric motor's rotor. In a worm-drive saw, however, the motor drives the blade from the rear.
The worm-drive mechanism that connects the motor to the saw arbor or shaft consists of two gears. One is cylindrical in shape and threaded like a screw. This is the “worm gear” attached to the arma-ture of the motor, which in turn drives a wheel-shaped gear called the worm wheel. The worm wheel is attached directly to the arbor shaft onto which the saw blade is fastened.
The advantage of the worm-drive saw is that it delivers the high revolutions of the engine to the saw blade at a much reduced rate of speed. This means that the torque (rotational force) is much greater, making tasks like cutting double thicknesses of dimensional lumber or several sheets of plywood much easier. The saw just keeps on cut-ting without the complaints or stalling you would get from most sidewinder (that is, traditional configuration) circular saws under such circumstances. When forced, a worm-drive saw is much less like-ly to kick back than a sidewinder saw.
Many experienced framing carpenters prefer worm-drive saws. The worm-drives are heavier (some weigh twice as much as direct- drive models) but the added power more than compensates. They are a bit more convenient for right-handers because the blade is to the left of the motor, and you can see the cutting edge without lean-ing over the saw.
A worm-drive circular saw is not an appropriate tool for the oc-casional user, not least because it is significantly more expensive than sidewinder saws. But it's a real workhorse designed for long, hard use. So, for building that big barn you've been thinking about… it just might be the answer.
Sliding Circular Saws
This is something of a catchall term, but one I find conven-ient to describe several differ-ent saws that are of related design. The classic Delta sawbuck belongs here, as do the new breed of chop boxes called sliding or “pull-through” miter saws.
The hinged blade assembly on a sliding saw swings down like a paper cutter. What distin-guishes it from the miter saw from which it evolved is that a pair of rods also allows it to be drawn toward the operator. This sliding action means you can cut wider stock than with a stand miter saw (some models will cut twelve-inch widths). Most models also tilt and turn, allowing miter and bevel cuts. Saws of the sawbuck school don't swing down, but do slide, tilt, and turn.
These tools are more versatile than the basic miter saw; on the other hand, they don't offer all the options of a radial-arm saw. But for those woodworkers who do a minimum of ripping and don't need to make moldings or do sanding jobs on the cut-off saw, a sliding circular saw may be an economical and portable option. These saws can be stored and moved easily and require a minimum of alignment.