Circular saw blades are toothed discs that can cut a variety of materials using a rotary motion. They can be mounted on chainsaws that cut 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 is important that the diameter of the blade matches your cutting requirements and the specific RPM (speed) of the blade and saw blade. This means that the diameter of the saw blade you choose must not exceed the maximum diameter it is designed for. When choosing a blade, be sure to read the size label carefully and check the power tool requirements. The blade diameter will usually be printed on the surface of the circular saw blade, along with the shaft hole size, number of teeth, and kerf (the thickness of the kerf the blade makes)
A number of teeth:
TLDR; More Teeth: Smoother, finer cuts. Fewer Teeth: Faster, rougher cuts.
The correct number of teeth is important to ensure a smooth cut, optimal chip evacuation, and as little friction as possible during the sawing process. The correct number of teeth will also reduce stress on the equipment, thereby extending the life of the saw.
Tooth size:
Blades with farther-apart teeth are great for rip cuts (woodworking cuts that cut a piece of wood parallel to the grain). This is because the large space between the teeth (esophagus) allows the sawdust to pass out quickly. On the other hand, smaller teeth give a better finish and are therefore ideal when making cross-cuts (cutting the grain of wood or materials).