Machinery's Handbook, 31st Edition
872 Milling Cutters Example: Determine the required number of teeth in a face mill where D = 6 inches and W = 4 inches. Using Formula (1), T 4 6.3 6 10 teeth, approximately # = = Example: Determine the required number of teeth in a plain milling cutter where D = 4 inches and d = 1 ⁄ 4 inch. Using Formula (2), T 4 4 4 1 12.6 4 cos0 10 teeth, approximately # # # = + = ° a k In high-speed milling with sintered carbide, high-speed steel, and cast nonferrous cut ting tool materials, a formula that permits full use of the power available at the cutter but prevents overloading of the motor driving the milling machine is: (3) where T = number of cutter teeth; H = horsepower (kilowatts) available at the cutter; F = feed per tooth in inches (mm); N = revolutions per minute of cutter; d = depth of cut in inches (mm); W = width of cut in inches (mm); and K = a constant that may be taken as 0.65 for average steel, 1.5 for cast iron, and 2.5 for aluminum. For metric units, K = 14278 for average steel, 32949 for cast iron, and 54915 for aluminum. These values are conservative and take into account dulling of the cutter in service. Example: Determine the required number of teeth in a sintered carbide-tipped face mill for high-speed milling of 200 BHN (Brinell Hardness Number) alloy steel if H = 7.5 kilowatt; F = 0.2032 mm; N = 272 rpm; d =3.2mm; W = 152.4 mm; and K for alloy steel is 14278. Using Formula (3), T 0.2032 272 3.2 152.4 14278 7.5 4 teeth, approximately # # # # = = American National Standard Milling Cutters.— According to American National Stan- dard ANSI/ASME B94.19-1997 (R2019), milling cutters may be classified in two general ways, given as follows: By Type of Relief on Cutting Edges: Milling cutters may be described on the basis of one of two methods of providing relief for the cutting edges. Profile sharpened cutters are those on which relief is obtained and which are resharpened by grinding a narrow land back of the cutting edges. Profile sharpened cutters may produce flat, curved, or irregular surfaces. Form relieved cutters are those which are so relieved that by grinding only the faces of the teeth the original form is maintained throughout the life of the cutters. Form relieved cutters may produce flat, curved or irregular surfaces. By Method of Mounting: Milling cutters may be described by one of two methods used to mount the cutter. Arbor type cutters are those which have a hole for mounting on an arbor and usually have a keyway to receive a driving key. These are sometimes called Shell type. Shank type cutters are those which have a straight or tapered shank to fit the machine tool spindle or adapter. Explanation of the “Hand” of Milling Cutters.— In the ANSI/ASME Standard, the terms “right hand” and “left hand” are used to describe hand of rotation, hand of cutter and hand of flute helix. Hand of Rotation or Hand of Cut is described as either “right hand” if the cutter revolves counterclockwise as it cuts when viewed from a position in front of a horizontal milling machine and facing the spindle, or “left hand” if the cutter revolves clockwise as it cuts when viewed from the same position. T F N d W K H # # # # =
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