448 Modern Metalworking Copyright Goodheart-Willcox Co., Inc. 26.4.1 Types of Milling Cutters Commonly used milling cutters include end, face, and arbor milling cutters. The following paragraphs pro- vide a brief description of these cutters and the work to which they are best suited. End Milling Cutters An end milling cutter, or r r end mill, is a milling cutter designed to mill slots, keyways, pockets, and similar work. The cutting edges are on the circumference and end. With the proper cutting speed, a cut with a depth equal to one-half the cutter diameter can generally be taken in solid stock. End mills may have straight or helical flutes, Figure 26-15A, and may have straight or taper shanks. Straight-shank end mills are available in single- and double-end styles, Figure 26-15B. End mills are typi- cally employed where arbor milling cutters cannot be used. Several styles of end mills are available: • A two-flute end mill can be fed into the work like a twist drill. There are two cutting edges on the circumference, with the end teeth sharpened to the center, Figure 26-16A. • The multiflute end mill has from three to fifteen cutting edges on its circumference, with the end teeth sharpened to the center. It can be run at the same speed as a comparable two-flute end mill, but it has a longer cutting life and produces a better finish. It is recommended for conventional milling where plunge cutting (feeding into the work like a twist drill) is not necessary, Figure 26-16B. Helical-fluted end mills Straight-fluted end mills Face-type cutter Double-end type end mill cutter A B Face type cutter Mitsubishi Materials USA Corp Goodheart-Willcox Publisher Figure 26-15. A—Examples of helical- and straight-fluted end mills, as well as two face cutters. All the cutters have indexable inserts. B—A double-end end mill and three large single-end end mills. Goodheart-Willcox Publisher Goodheart-Willcox Publisher Figure 26-16. A—A two-flute end mill can be fed into the work like a drill. B—Multiflute end mills. The peripheral grooves in the bottom roughing cutter reduce chip sizes, lowering cutting forces. Most modern cutters have a nitride coating that improves resistance to abrasion and corrosion. A B