More so than the brand of saw blade, getting the correct type of blade determines whether you'll get a quality cut. And in most instances, your new tool's factory-supplied blade may be better suited for job-site cutting than woodworking. Here are eight things you need to know to get the right blade for the job.
■ Diameter. Okay, this one's easy. Each tool generally accepts a specific size blade: typically 10" for tablesaws, 61⁄2 " or 71⁄4 " for handheld circular saws, 10" or 12" for mitersaws and radial-arm saws. Some tools can use a smaller blade (see dado blades, below), but never attempt to use a larger one. It might be difficult to find replacement blades in some sizes; your tool-buying decisions may hinge on the availability of blades.
■ Kerf. This refers to the width of the cut made by a blade. The thicker the blade, the less likely it is to flex (and the wider the kerf). So, heavy-duty stationary tablesaws generally use 1⁄8 "-kerf blades because those saws can easily power that blade through dense hardwoods. Tablesaws with motors rated at 11⁄2 hp or less, as well as mitersaws and radial-arm saws, get more apparent power with thin-kerf blades (about 3⁄32 "). Portable circular saws—especially battery-powered ones—use even thinner blades; it's almost impossible to find 1⁄8 "-kerf blades for portable saws. These ultrathin blades put less strain on the saw motor and because of their smaller diameters don't flex noticeably.
■ Tooth grind. Almost every blade used today has carbide teeth, which stay sharp far longer than all-steel blades. Manufacturers grind the teeth to the shape best suited for a specific cutting action. If you look into the face of the teeth (as shown below), you'll see the tooth grind. An alternate-top-bevel (ATB) grind has teeth with alternating left- and right-pointing tips, made to minimize tear-out in wood and veneered plywood. General purpose, crosscutting, and plywood/melamine blades use this grind.
Rip blades, used to cut wood parallel to the grain, have flat-top teeth with no bevel. This helps clear debris from the kerf. Combination blades use a mix of ATB teeth and flat-topped teeth, and do better at crosscutting than general-purpose blades, but don't rip as well. Blades used primarily to cut solid-surface countertops and melamine-coated particleboard use a triple-chip grind to prevent tear-out.
■ Hook angle. This refers to the angle of the tooth face, as viewed from the side. As shown below, if you draw a line from the center of the arbor hole to the leading edge of a tooth, you'll see its positive (leaning forward) or negative (leaning backward) hook angle. The more positive the angle, the more aggressively the blade cuts. Use a high positive hook angle (5° to 20°) on a tablesaw for general crosscutting and ripping, and a steeper angle (up to 30°) for cutting melamine-coated particleboard and veneered plywood.
Sliding mitersaws and radial-arm saws require a negative hook angle (-5° to -10°) to reduce the saw's tendency to lurch forward too quickly during a cut. Portable circular saws and non-sliding mitersaws work best with blades that have a hook angle of 5° to 0°. But be aware: Not all blade manufacturers list the hook angle on their blades or packaging, so do your research before buying.
■ Tooth count. Although general-purpose and combination blades work well at multiple tablesaw tasks, you'll get the best results by choosing the right blade based on its number of teeth. Tablesaw rip blades have 24–30 teeth, with deep gullets for waste removal. Crosscutting blades have high tooth counts: 60–80 are best for tablesaws, 10" mitersaws, and radial-arm saws; 80–100 for 12" mitersaws and radial-arm saws. Cutting plywood on a tablesaw calls for an 80-tooth blade. Portable circular saws rip best with 10–12-tooth blades, crosscut best with 40 teeth, and cut veneered plywood best with 60 teeth.
■ Dado blades. Tablesaws (and some radial-arm saws) accept a stacked dado set, shown below, for cutting one-pass dadoes, grooves, and rabbets up to 7⁄8 " wide, depending on the machine. These sets consist of two outer blades (one with left-beveled teeth and the other beveled to the right) and inner chipper blades (with flat topped teeth). Stack any combination of chippers between the outer blades to get the channel width you need.
■ Arbor hole. The hole in the center of each blade is sized to match the arbor (blade-drive shaft) of your saw. Most blades 10" or less in diameter mount on a 5⁄8 " arbor, but 12" blades use a 1" arbor. And many saws manufactured by Skilsaw use a proprietary diamond-shaped mounting system, below.
■ Blade coating. Some blades come with a coating on the plate meant to reduce friction, rust, and resin buildup. Don't make this aspect a high priority when buying blades.