446 Modern Metalworking Copyright Goodheart-Willcox Co., Inc. In peripheral milling operations, the machined g surface is parallel to the periphery (external surface) of the cutter, Figure 26-11. Examples of peripheral milling include slab milling, slotting, side milling, straddle milling, and form milling. These forms of peripheral milling will be explained in more detail in the horizontal milling operations section of the chapter. 26.3 Milling Methods The two basic methods of milling are conventional and climb milling. In conventional milling, or g g up-milling, the work is fed into the rotation of the g g cutter, Figure 26-12A. The chip is at minimum thick- ness at the start of the cut. It is also so light that the cutter has a tendency to slide over the work until enough pressure builds up to cause the cutter teeth to “bite” into the work. In climb milling, or g g down-milling, the work g g moves in the same direction as the cutter rotation, Figure 26-12B. Full engagement of each tooth is instantaneous. The main advantage of climb milling is that the cutting action presses the work down on the worktable or holding device, which helps prevent the sliding action that occurs in conventional milling. This results in a better surface finish and longer tool life. However, climb milling is not recommended on light milling machines or on older machines that are not in top condition or are not fitted with an antibacklash device to take up lead screw play. 26.4 Milling Cutters A typical milling cutter is circular in shape with a r number of cutting edges (teeth) located around its circumference. Milling cutters are available in a wide range of stock shapes and sizes, because they cannot be economically ground for a particular job as can a lathe cutter bit. Milling cutters are either solid or inserted-tooth cutters. A solid cutter is one in which the shank r and body are made in one piece, Figure 26-13A. An inserted-tooth cutter has teeth that are brazed or r clamped in place, Figure 26-13B. This type of cutter is also known as an indexable insert cutter. Worn and r r broken teeth can be replaced easily on these cutters. Milling cutters are frequently classified by the method used to mount them on the machine: • Shank cutters have a straight or taper shank that is an integral part of the cutter, Figure 26-14A. They are held in the machine by collets or sleeves. • Facing cutters can be mounted directly to the spindle nose or on a stub arbor, Figure 26-14B. • Arbor cutters have holes for mounting on an arbor, Figure 26-14C. Goodheart-Wilcox Publisher Figure 26-11. In peripheral milling, the surface being machined is parallel to the periphery of the cutter. A B Goodheart-Willcox Publisher Figure 26-12. Milling methods. A—Cutter and work movement with conventional (up) milling. B—Cutter and work movement with climb (down) milling.