Chapter 24 Machining Processes: Milling, Broaching, Sawing, Filing, and Gear Manufacturing

FIGURE 24.1 Typical parts and shapes that can be produced with the machining processes described in this chapter.

FIGURE 24.2 Some basic types of milling cutters and milling operations. Source: Courtesy of Sandvik Coromant.

FIGURE 24.3 The cutting action of a milling cutter using a number of inserts to remove metal. Source: Courtesy of Sandvik Coromant.

MILLING AND MILLING MACHINES 1. PERIPHERAL MILLING 2. FACE MILLING 3 MILLING AND MILLING MACHINES 1. PERIPHERAL MILLING 2. FACE MILLING 3. END MILLING 4. OTHERS

MILLING AND MILLING MACHINES 1 MILLING AND MILLING MACHINES 1. PERIPHERAL MILLING axis of cutter is parallel to the surface of work piece = conventional milling (up milling): max. ghip thickness is at the end of the cut =climb milling (down milling) : cutting starts at the surface of the chip where the chip is thickest =slab milling: when cutter is longer than the width of cut

FIGURE 24.4 Schematic illustration of peripheral milling.

FIGURE 24.5 (a) Schematic illustration of conventional milling and climb milling. (b) Slabmilling operation showing depth of cut, d; feed per tooth, f ; chip depth of cut, tc , and workpiece speed, v. (c) Schematic illustration of cutter travel distance, lc , to reach full depth of cut.

MILLING AND MILLING MACHINES 2 MILLING AND MILLING MACHINES 2. FACE MILLING axis of rotation of cutter is perpendicular to the surface of work piece

FIGURE 24.6 (a) Face-milling operation (with cutter removed) showing the action of a single insert; (b) climb milling; (c) conventional milling; and (d) dimensions in face milling. Note that the width of cut, w, is not necessarily the same as the cutter radius.

FIGURE 24. 7 A face-milling cutter with indexable inserts FIGURE 24.7 A face-milling cutter with indexable inserts. Source: Courtesy of Ingersoll Cutting Tool Company

FIGURE 24.9 Terminology for a face-milling cutter.

MILLING AND MILLING MACHINES 3 MILLING AND MILLING MACHINES 3. END MILLING The cutter usually rotates on an axis perpendicular to the work piece surface The cutter is called end mill. Hollow end mills have internal cutting teeth and are used to machine the cylindrical surfaces of solids High speed end milling: high rates of material removal but chip collection and disposal might be a problem

MILLING AND MILLING MACHINES 4 MILLING AND MILLING MACHINES 4 . OTHER MILLING OPERATIONS - straddle milling - form milling - slotting - slitting

FIGURE 24.14 Cutters for (a) straddle milling; (b) form milling; (c) slotting; and (d) slitting with a milling cutter.

FIGURE 24. 15 (a) T-slot cutting with a milling cutter FIGURE 24.15 (a) T-slot cutting with a milling cutter. (b) A shell mill.

MILLING MACHINES 1. Column and knee type machines 2 MILLING MACHINES 1. Column and knee type machines 2. Bed type milling machines

MILLING MACHINES 1. Column and knee type machines the spindle on which milling cutter is mounted is vertical or horizontal Machine components -worktable - knee -overarm -head -base

FIGURE 24.18 Schematic illustration of (a) a horizontal-spindle column-and-knee type milling machine and (b) vertical-spindle column-and-knee type milling machine. Source: After G. Boothroyd.

MILLING MACHINES 2. Bed type milling machines the worktable is mounted directly on the bed, which replaces the knee, and moves only longitudinally

FIGURE 24.19 Schematic illustration of a bed-type milling machine.

PLANING AND SHAPING 1. Planing relatively simple machining operation by which flat surfaces as well as cross sections with grooves can produced along the length of the work piece work piece is mounted on a table that moves back and forth usually done on large work pieces (10m or more)

PLANING AND SHAPING 2. Shaping similar to planing the tool travels not the work piece work piece is smaller (2 m) horizontal shaper: cutting tool moves back and forth vertical shapers: called slotters are used to machine kkeyays has low production rates

BROACHING similar to shaping, but with a multiple tooth cutter used to machine internal and external surfaces Examples: holes of any section, teeth of internal gears, flat surfaces produces parts with good surface finish and dimensional accuracy competes with boring, milling, shaping and reaming broaches are expensive, but cost is justified by high quantity production

FIGURE 24. 23 (a) Typical parts made by internal broaching FIGURE 24.23 (a) Typical parts made by internal broaching. (b) Parts made by surface broaching. (c) A spline broach and internal spline used for a shaft coupling. (d) Vertical broaching machine. Source: (a) and (b) Courtesy of General Broach Company, (c) Courtesy of The Broachmasters, Inc., and (d) Courtesy of Ty Miles, Inc.

FIGURE 24. 24 (a) Cutting action of a broach, showing various features FIGURE 24.24 (a) Cutting action of a broach, showing various features. (b) Terminology for a broach.

FIGURE 24.25 Chip breaker features on broaches.

FIGURE 24.26 Terminology for a pull-type internal broach, used for enlarging long holes.

BROACHING MACHINES Simple in construction Have only linear motion either pull or push the broaches either vertical or horizontal

SAWING cutting tool is a blade (saw) Consists of several teeth Can be used for all materials width of the cut is called the kerf is small so the process wastes no material saw blades are made from carbides, high carbon steels, high speed steels

TYPES OF SAWS 1. Hacksaw: straight blades 2 TYPES OF SAWS 1. Hacksaw: straight blades 2. Circular saws (cold saws): have a variety of tooth profiles. The process is called cutting off. 3. Band saws: long flexible blades 4. Friction sawing: mild steel disc which rubs against work piece. Work piece properties along the cut edges can be adversely affected by the heat generated

FIGURE 24.28 Examples of various sawing operations.

FIGURE 24. 29 (a) Terminology for saw teeth FIGURE 24.29 (a) Terminology for saw teeth. (b) Types of tooth sets on saw teeth, staggered to provide clearance for the saw blade to prevent binding during sawing.

FIGURE 24. 30 (a) High-speed steel teeth welded onto a steel blade FIGURE 24.30 (a) High-speed steel teeth welded onto a steel blade. (b) Carbide inserts brazed on blade teeth.

FILING small scale removal of material from a surface, corner or hole FILING small scale removal of material from a surface, corner or hole. Includes the removal of burs files are made of hardened steel are available in a variety of cross sections (flat, half-round, square, triangular) have several coarseness grades usually done by hand, yet filing machines are available

Types of files 1. Band files 2. Disc type files 3 Types of files 1. Band files 2. Disc type files 3. Rotary files and burs

FIGURE 24.32 Types of burs used in burring operations.

GEAR MANUFACTURING BY MACHINIG Gears can be produced by: casting, forging, extrusion. Drawing Gear sizes vary from very small (watches) to very large (9 m in diameter) in mining equipment

FIGURE 24.33 Nomenclature for an involute spur gear.

FORM CUTTING OF GEARS

FIGURE 24. 34 (a) Producing gear teeth on a blank by form cutting FIGURE 24.34 (a) Producing gear teeth on a blank by form cutting. (b) Schematic illustration of gear generating with a pinion-shaped gear cutter. (c) and (d) Gear generating in a gear shaper using a pinion-shaped cutter; note that the cutter reciprocates vertically. (e) Gear generating with rack-shaped cutter. Source: (d) Courtesy of Schafer Gear Works, Inc.