Saws are a workhorse in the woodworking shop, and use of the correct blade is essential for a quality product. The following is a primer on some of the basic tooth types and their advantages and disadvantages for use on different substrates and materials.
Flat top: typically used for ripping wood. Advantages: Cuts both sides of the kerf simultaneously, making it twice as effective as teeth in a staggered tooth saw in which each tooth cuts only one side at a time; and has large included angles between the cutting edges that strengthen the tooth form and keep it sharp for longer periods of time. Disadvantages: The tooth form generates a relatively large cutting pressure which can lead to chip out or tear out; and the low side clearance angles inhibit the freedom of chip flow, which can cause a buildup.
Alternate Top Bevel (ATB): typically used for general purpose and crosscut saw blades. Advantages: It produces very low cutting pressures that almost eliminate the tendency to tear out; and the spaces created by the large side clearance angles allow the chips to fall free. Disadvantages: The leading point is susceptible to wear and damage from shock loads; and the cutting forces perpendicular to the beveled edge result in semi-lateral thrusts on the saw body.
Hi-Alternate Top Bevel (HI-ATB): designed for cutting acrylics and melamine. Advantages: Gives an extra fine cut; for man-made materials when a scoring unit is not used. Disadvantages: The leading point is extremely susceptible to wear and damage from shock loads; cannot be used for solid wood; and the cutting forces perpendicular to the beveled edge result in semi-lateral thrusts on the saw body.
4 Tooth and Raker (4&1): general purpose blades, rips and crosscuts equally well for a smooth cut. Advantage: Produces very low cutting pressures that almost eliminate the tendency to tear out. Disadvantages: The leading point is susceptible to wear and damage from shock loads; in sharpening, it is difficult to maintain an equal bevel diameter across the points of the teeth around the saw.
Conical Form: used on scoring blades. Advantages: Large included angles in the cutting edges give the triple chip form good wear resistance; balanced cutting force; and low tooth drag. Disadvantages: The triple chip tooth form requires extra maintenance care to avoid the risk of changing tooth forms during sharpening; and the form’s blunt edges make for a relatively low shear, generating high cutting pressures which tend to produce chip outs.
Source: General Saw Corp. For information call 800-306-7297 or visit GeneralSaw.com.