Arbor Hole The size of the arbor hole is generally larger on blades with a larger diameter. Commonly referred to as the bore, blades up to 10″ (254 mm) in diameter have a 5/8″ (16 mm) bore. Larger blades, such as 12″, 14″, and 16″ (305 mm, 356 mm, and 406 mm), have a 1″ (25 mm) bore. Other Considerations Between each tooth is a gullet. It is where chips accumulate as teeth cut through the material. The chips absorb heat from the blade and are then thrown out when the tooth exits the stock. Circular blades are either flat, hollow ground, or thin rim. See Figure 23-59. Flat blades are set to create a wider saw kerf. The teeth are larger than the blade to create a kerf slightly wider than the steel plate. The kerf prevents the blade body from bind- ing. A hollow ground blade leaves a smoother cut edge on the workpiece. The thinner cross section of the blade reduces binding. However, binding and heating will occur if the blade is not raised at least 1″ (25 mm) above the stock. A thin rim (thin kerf) blade creates the narrowest kerf and thus, conserves material. However, heat buildup is a problem with thicker material. Most blades are designed with expansion slots. See Figure 23-60. These relieve heat stress in the blade. A warm blade will warp and affect the smoothness and width of the kerf. On carbide blades over 12″ (254 mm) in diameter, holes at the bottom of the expansion slots are sometimes fitted with alumi- num plugs. These help reduce noise and vibration, resulting in a smoother cut. 23.10.2 Band Saw Blades A band saw blade is an endless bonded loop of thin narrow steel with teeth on one edge. Select band saw blades according to various specifications. The length of the loop is critical. While it is possible to buy 100′–500′ (30.5 m–152 m) coils and cut and weld together your own blades, most users buy blades sized for their machine Your machine manual will specify the correct length needed. Blade width is important. It may vary from 1/8″ to 1″ (3 mm to 25 mm) or wider. Blades 1/8″–1/2″ (3 mm–13 mm) are used most often for sawing curves. Wider blades are more appropriate for resawing. Blades vary in hardness. Some inexpensive blades are made of untempered steel. Others may have a flame-hardened cutting edge and possibly a hard-tempered back. There are several alternative tooth shapes and blade sets available. See Figure 23-61. A regular blade has a 0° hook angle and a straight front and back on each tooth. A hook-tooth blade has about a 10° positive hook angle. A skip-tooth blade has a straight tooth front, 0° hook, and a long gullet. Regu- lar and hook-tooth blades have teeth set alternately left and right. Skip-tooth blades may have a raker tooth set. A third set-type is the wavy tooth blade. Several teeth are set right and then left. They are separated by a raker tooth. A regular blade works best for wood only. The hook-tooth cuts well on most wood, fiberglass, and plastic laminate. The skip-tooth blade is better for soft woods and plas- tics. These materials tend to overload and clog other blades’ gullets. Blades with carbide teeth are also available. They offer more precise cuts, increased wear resis- tance, and the ability to cut composite materials. Although expensive initially, carbide will outlast carbon steel blades by as much as 25 to 1, and they can be resharpened. Patrick A. Molzahn Figure 23-60. Expansion slots are cut into the blade to prevent warping as the blade heats up during use. Coatings can also reduce heat buildup by reducing friction. Goodheart-Willcox Publisher Figure 23-59. Circular blades are either flat, hollow ground, or thin rim. Flat Hollow Ground Thin Rim Blade Cross Section 402 Section 4 Machining Processes Copyright Goodheart-Willcox Co., Inc.