While there are many types and sizes of circular Saws on the market, I would like to discuss what I believe to be the three most prominent categories. They are: plunge Saws with guide rails, worm drive or hypoid Saws for building use and standard-drive circular saws convenient for both home and building use. Before I delve into all of that, however, I'd like to take a quick look at the basics.
A circular saw allows you to take a relatively small tool to a large work piece and cut it without too much back-breaking labor. In the past, the price for this convenience was inaccuracy because there was no truly easy way to force a circular saw to cut right along a pencil line. For rough building work like roofing and decking, this was no problem. For fine woodworking, however, the circular saw was not the tool of choice. Most woodworkers rely on the table saw to get the long, right cuts they need and for good reason. The fence on a table saw gives the constant reference point needed for right cuts.
Sometimes, however, using a table saw to trim the top of a huge consulation table, for instance, turns out to be an impossible task, especially when trying to trim off the ends at 90 degrees to the sides. That's when a very carefully planned arrival using a circular saw seems to deliver the best final result. I would draw a pencil line using a long straightedge exactly where I wanted the trim cut to go. I would then carefully portion the length in the middle of the inside (or outside) of the saw blade and the edge of the foot plate of the saw. The next step would be a second pencil line, parallel to the first one and separated from it by the length I measured in the middle of the inside (or outside) of the saw blade and the edge of the foot plate. I would uncover an truly right board (ripped right on the table saw, if necessary) and clamp this across the table top as a guide along the second pencil line. Then, I could make a pretty right cut along the first pencil line. I would then repeat this for the other end of the table top.
In the past few years, this process has become a whole lot easier. There are now some makes and models of plunge saws that run along metal guide rails, cutting right next to the edge of the rail without cutting into the rail itself. The guide rails don't even need to be clamped to the exterior being cut because they have material underneath that keeps them from sliding around. If you feel more comfortable clamping down the guide rail, this can be done, as well. It's a uncomplicated matter to lay the guide with its edge along the cut line and then to take the saw and run it down the rail, cutting right next to the lip of the rail.
Because these saws are plunge-type saws, you can begin and/or end a cut in the middle of a sheet of plywood. You could cut out a window or door opening, for instance and have it come out clean and quadrilateral every time. The best thing about using these track saws is the reliance they give you: You Know you can do a exquisite job, quickly, accurately, over and over again.
Another kind of circular saw I've used a lot over the years, mostly for construction, is the worm drive saw pioneered by Skil. A framing carpenter needs to be able to cut a lot of lumber all day long. While accuracy is all the time desirable, it is not as vital to the framer as it would be to a terminate carpenter or cabinet maker. Speed is the thing that the framer wants on his side and he (or she) does not want to be saddled with a saw that can't cut the mustard, so to speak. He doesn't want his circular saw to bog down in the middle of cutting a 2 x10 joist or have the sole plate hang up every time it goes across the edge of someone else board. He does not want to have the saw blade slipping nearby the saw arbor. What he wants is clean, fast precise cuts: In short, power.
A worm drive saw delivers the constant power he needs because there is no slack or play everywhere in the middle of the remarkable motor and the saw teeth that are doing the cutting. The worm gear cuts down a bit on saw blade Rpm but trades this off for torque. It is torque, more than speed, that powers a saw blade through thick, wet wood. A diamond-shaped arbor makes it virtually impossible for the blade with a matching diamond-shaped hole to rotate nearby the arbor. Keeping the number of saw teeth down to 18-24 teeth on a 7 1/4" saw blade also helps. The only qoute with early Skil worm drive saws was the weight with those large motors and all that gearing. The clarification was to use magnesium instead steel in the building of the saw wherever possible. The contemporary magnesium worm drive saws weigh only about 14 to 15 pounds which is more than a acceptable circular saw but manageable in the strong hands of a muscular framer.
The final type included the kind of saw that most habitancy think of as a circular saw. It is lighter than the worm drive saws and, for most uses, it's plenty remarkable enough. Some of these saws are now also be made out of magnesium parts and weigh just over 10 Lbs. This makes them easy to use by the midpoint do-it-yourselfer. Did I mention that they are a lot less high-priced than the other types?
