Chapter 11 Sawing and Cutoff Machines 163 Copyright Goodheart-Willcox Co., Inc. copper, and soft brasses. The hook tooth blade pattern is recommended for most nonferrous metallic materials. See Figure 11-13. For best results, consult the blade manufac- turer’s chart or manual for the proper blade characteristics (set, pattern, and number of teeth per inch) for the particular material being cut. A new development in saw blades is the stepped-back band saw blade. The stepped-back band saw blade has a pat- terned edge on the back of the blade opposite the cutting teeth. This design works with opposing guides that are posi- tioned on either side of the workpiece. The guides provide downward pressure onto the back edge of the blade, caus- ing the blade to rock in an up-and-down motion as the teeth are being fed through the workpiece. The rocking motion allows the cutting speed of the saw to be increased, Figure 11-14. The rocking motion also prevents the cutting teeth from constantly riding on surfaces that are parallel to the cut, resulting in longer blade life. This is particularly advantageous when cutting workpieces that have large cross- sectional areas. 11.3.2 Installing a Band Saw Blade SAFETY NOTE Wear heavy leather gloves to protect your hands when installing a band saw blade. Careful blade installation allows the saw to work at top efficiency. Adjust the blade guides to provide adequate sup- port, Figure 11-15. Proper blade support is required to cut true and square with the holding device. Straight Tooth Set Wavy Tooth Set Raker Tooth Set Goodheart-Willcox Publisher Figure 11-12. Saw blades commonly have straight, raker, or wavy teeth. Raker teeth are preferred for general use, cutting large solid sections, and cutting thick plate. Standard Tooth Skip Tooth Hook Tooth Goodheart-Willcox Publisher Figure 11-13. Standard tooth blades, with rounded gullets, are usually best for ferrous metals, hard bronzes, and hard brasses. Skip tooth blades provide for more chip clearance without weakening the blade body. They are recommended for cutting aluminum, magnesium, copper, and soft brasses. Hook tooth blades offer two advantages over skip tooth blades: easier feeding and less “gumming up.” Blade Tilted Guides Guide in indentation Blade Tilted Blade Horizontal Direction of cut Guide in indentation Indentation Goodheart-Willcox Publisher Figure 11-14. A stepped-back band saw blade fi ts with opposing guides to achieve an up-and-down motion that allows saw speed to increase.