Circular saw blades are discs with teeth that can cut a range of materials using a spinning motion. They can be fitted to power saws cutting many materials such as wood, masonry, plastic, or metal. Most circular saws come standard with a 7¼-inch-diameter blade and a motor that draws 8 to 15 amps of power.
Blade Diameter:
For safety reasons, it’s very important that the blade is the correct diameter for your cutting requirements and the specific RPM (speed) of your blade and saw. This means that the diameter of the saw blade you select must not exceed the maximum diameter of the blade designed to use with your saw. When selecting your blade, be sure to carefully read the measurements of the label and to check the requirements of your power tool. The blade diameter will usually be printed on the face of a circular saw blade, along with the arbor hole size, number of teeth, and kerf (the thickness of the cut the blade creates)
The Number of Teeth:
TLDR; More teeth: Smoother, finer cut. Fewer teeth: Faster, rougher cut.
The correct number of teeth is important to ensure that you achieve a smooth cut with optimal chip removal and as little friction as possible whilst sawing. The correct number of teeth will also place less strain on your equipment, extending the lifespan of your power saw.
The Size of the Teeth:
Blades with larger teeth spaces further apart are ideal for making rip cuts (cuts made in woodworking to sever a piece of wood parallel to the grain). This is because large spaces between the teeth (gullets) allow the sawdust to be expelled quickly. Smaller teeth, on the other hand, allow for a better finish, so are ideal when making crosscuts (cutting across the grain of the wood or material).