Cutting Edge There are various standard blade cutting edges. The cutting edges are determined by the tooth shape. The type of material and grain direction through which a blade will cut is based on the tooth shape. Teeth may be flat-top (square), bevel shaped, or a combination of the two shapes. Some combina- tion blades may have teeth shaped several ways. For example, one tooth is square followed by several that are beveled. The cutting edge of carbide tips are ground to various shapes, commonly referred to as grinds, Figure 23-58. The most popular grinds and uses are as follows: • Flat-top (FT) grind. The blade has larger gullets, fewer teeth, and will accept greater chip loads for higher feed rates. See Figure 23-58A. Excellent for ripping solid wood when speed is more important than cut quality. • Alternate top bevel (ATB) grind. Top bevel shaped teeth sever the material with a shearing action, alternating left and right. See Figure 23-58B. This grind is used for crosscut- ting or a combination of crosscuts and rip cuts. Blades of this design with a high number of teeth will produce a higher quality of finish cut in wood. Blades with a high bevel angle (30°) are able to produce superior cuts on both sides of thermofused melamine and HPDL panels. Use blades with a negative hook angle for improved control over feed rate. • Alternate top bevel with raker grind. Two sets of alternate left and right top bevel teeth are followed by a raking action flat-top tooth with large round gullet to ease chip removal. See Figure 23-58C. This is an excellent choice for a combination blade. • Triple-chip (TC). Triple-chip teeth are beveled on both sides with a small flat on the top edge. Some blades alternate triple-edge teeth with flat-top teeth for dual-action cutting. See Figure 23-58D. The triple-chip teeth remove material from the center of the kerf, followed by the flat-top raker to clean out remaining mate- rial from both sides. Excellent results can be achieved on plywood and plastics. They are often used on power miter and radial arm saws. Triple-chip blades with a negative hook angle are preferred for cutting nonferrous metal. Number of Teeth The number of teeth is an important aspect of blade design. The number does not distinguish a rip blade from a crosscut or combination blade. Rather, it suggests the performance of a blade when cutting thin materials. Generally, a blade with a larger num- ber of teeth will produce consistently smoother cuts. When cutting stock on a table saw, adjust the blade height so at least two teeth are always in the material. Kerf Width The width of the sawn kerf is generally larger on large diameter blades. This is due to the thicker plate used for larger blade diameters. The standard kerf for a 10″ (254 mm) diameter blade is 1/8″ (3 mm). Thin kerf models have a 3/32″ (2 mm) kerf design. The thin kerf design makes stock feeding excep- tionally smooth, easy, and fast. Smaller horsepower machines can handle more work with less strain on the motor and the operator. A common kerf for a 16″ (406 mm) diameter blade is 11/64″ (4 mm). Goodheart-Willcox Publisher Figure 23-58. Four popular tooth designs. A—Flat-top grind (FT). For cutting material with the grain. B—Alternate top bevel grind (ATB). For across-the-grain cutting. Higher quality of cut comes from blades with the highest number of teeth. C—Alternate top bevel with raker (ATB and R). Excellent for a combination of crosscutting and rip cutting. D—Triple-chip and flat grind (TC with FT). Primarily for use with composite products and plastics. Blades with a nega- tive hook angle are recommended for cutting nonferrous metals and for use on radial arm saws. Carbide Tipped Blades Tooth Shape Blade Shape Flat top (FT) Alternate Top Bevel (ATB) Triple-chip (TC) Rip Blade (FT) Crosscut Blade (ATB) Combination Blade (FT and ATB) Plastic Blade and Composite (TC with FT) B D A C Chapter 23 Sawing with Stationary Power Machines 401 Copyright Goodheart-Willcox Co., Inc.