Effect of Cutting Angles in Woodworking with Carbide and Steel Cutters

Carbide grade 883 straight knives 2-inches wide with a 4-inch diameter cutting circle were used. The 2-knife cutter head revolved at 7200 rpm in a climbing direction into the wood. A power indicator was used to note the power consumption required for the different cutting angles. The types of wood tested were: basswood, plain-grained yellow birch, curly grained yellow birch, and sugar maple. Panels consisting of a 11/16-inch core, faced with 1/28-inch birch veneer of characteristic grain, were selected to represent a general production run. The moisture content was between 7 and 9 percent. The depth of cut varied from 1/8 to 1/4 inch from a rough surface. The feed was at 16 feet per minute. Reduction of the cutting angle caused a greater force to be exerted in the direction of feeding, but a decreased force to be exerted at right angles to the face of the board being shaped. The high sharpness angles used with steel cutters are not necessary in the case of carbide cutters because they remain sharp longer and are not dependent upon a small sharpness angle to provide a narrow cutting edge after the cutter reaches a certain dull stage. Carbide sharpness angles should not be as small as tool steels since the granular nature of material will not support the stresses associated with small sharpness angles. Knife clearance angle should be kept to a minimum–10? to 15? for carbide and 15? to 25? for steel knives. The smaller the cutting circle the more clearance is required. Low density wood requires a larger cutting angle (25? to 35?) and a smaller sharpness angle. As a general rule for a given chip thickness, the quality of cut surface is best when a suitable chipbreaker can be used. To prevent raising the grain on green stock, increase the cutting angle and reduce the knife cuts per inch. To prevent tearing out on dry stock, decrease the cutting angle or increase the knife cuts per inch or use the climb cutting method.

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