Broaches and Broaching Machinery's Handbook, 31st Edition
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d
Double Keyway D
Single Keyway
4-Spline E
Hexagon F
Square
Round B
C
A
f f
Double-Cut H
Internal Gear I
Round J
Helical Groove K
Rectangular G
Fig. 1. Types of Broaches Burnishing Broach: This is a broach having teeth or projections that are rounded on the top instead of being provided with a cutting edge, as in the ordinary type of broach. The teeth are highly polished, the tool being used for broaching bearings and for operations on other classes of work where the metal is relatively soft. The tool compresses the metal, thus making the surface hard and smooth. The amount of metal that can be displaced by a smooth-toothed burnishing broach is about the same as that removed by reaming. Such broaches are primarily intended for use on babbitt, white metal, and brass, but may also be satisfactorily used for producing a glazed surface on cast iron. This type of broach is also used when it is only required to accurately size a hole. Pitch of Broach Teeth.— The pitch of broach teeth depends upon the depth of cut or chip thickness, the length of cut, the cutting force required and the power of the broaching machine. In the pitch formulas that follow L = length, in inches (mm), of layer to be removed by broaching d = depth of cut per tooth as shown by Table 1 (For internal broaches, d = depth of cut as measured on one side of broach or one-half difference in diameters of successive teeth in the case of a round broach.) F = a factor (For brittle types of material, F = 3 or 4 for roughing teeth and 6 for finishing teeth. For ductile types of material, F = 4 to 7 for roughing teeth and 8 for finishing teeth.) b = width in inches (mm) of layer to be removed by broaching P = pressure required in tons per square inch (MPa) of an area equal to depth of cut times width of cut, in inches (mm) (Table 2) T = usable capacity, in tons (metric tons), of broaching machine = 70 percent of maximum tonnage
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