Volume 16 - Machining Part 8 pps

Fig. 15 Three types of carbide inserts. (a) Brazed inserts. (b) Square indexable throwaway inserts. (c) Round (button-type) indexable inserts on a half-round broach Round (button-type) indexable carbide inserts are also used for broaching castings. They offer the same advantages as square or rectangular inserts with the additional benefit, in some applications, of longer tool life. A tool life of 85,000 workpieces per insert index has been reported. Less cutting force is required with round inserts because they have a reduced depth-of-cut capability, which may require lengthening the broaching stroke. On a unit-load basis, a round insert requires greater force than a square one. A half-round broach with double-sided button inserts retained by center screws is shown in Fig. 15(c). Inserts can be overlapped and mounted at a shear angle along the length of the broach to produce the required size progression and to balance the cutting load. Provided the holder is manufactured to close tolerances, particularly in those sections that determine the height of the cutting edge, gaging is not required when cutters are changed to present a new cutting edge. Disposable carbide cutters can be inserted in any position without removing the broach from the machine. To provide the required clearance behind the cutting edges, inserts must have a negative rake. Inserts for contour cutting can be sharpened on the top and face, and shimmed to the correct position. A considerable savings in tool cost is made possible by changing from brazed carbide tools to disposable carbide inserts for the same broaching operation. Internal and External Broach Configurations. A number of typical broaches and the operations for which they are intended are shown in Fig. 16. Fig. 16 Typical broaches and the configurations they generate. See text for discussion A square broach (Fig. 16a) produces a round-cornered, square hole. Prior to broaching square holes, it is common to drill a round hole having a diameter somewhat larger than the width of the square. Thus, the sides are not completely finished, but this unfinished part is not objectionable in most cases. In fact, this clearance space is an advantage during broaching in that it serves as a channel for the broaching lubricant; moreover, the broach has less metal to remove. A round broach (Fig. 16b) is for finishing round holes. Broaching is superior to reaming for some classes of work because the broach will hold its size for a much longer period, thus ensuring greater accuracy. Keyway broaches (Fig. 16c and d) are for cutting single and double keyways. The single keyway broach is of rectangular section and, when in use, slides through a guiding bushing inserted in the hole. The four-spline broach (Fig. 16e) is for forming four integral splines in a hub. The hexagon broach (Fig. 16f) is for producing hexagonal holes. A rectangular broach (Fig. 16g) is used for finishing rectangular holes. The teeth on the sides of this broach are inclined in opposite directions; this has the following advantages: • The broach is stronger than it would be if the teeth were opposite and parallel to each other • Thin work cannot drop between the inclined teeth, as it tends to do when the teeth are at right angles, because at least two teeth are always cutting • The inclination in opposite directions neutralizes the lateral thrust The teeth on the edges are staggered, the teeth on one side being midway between the teeth on the other edge, as shown by the dotted line. A double-cut broach (Fig. 16h) is for finishing, simultaneously, both sides of a slot and for similar work. An internal gear broach (Fig. 16i) is the style used for forming the teeth in internal gears. It is a series of gear-shaped cutters, the outside diameters of which gradually increase toward the finishing end of the broach. A round broach (Fig. 16j) is for round holes, but differs from the broach shown in Fig. 16(b) in that it has a continuous helical cutting edge. The broach shown in Fig. 16(j) produces a shearing cut. A helical groove broach is for cutting a series of helical grooves in a hub or bushing. In helical broaching, either the work or the broach is rotated to form the helical grooves as the broach is pulled through. Rotary-Cut Broaches. Rough forgings, malleable iron castings with a hard skin, and sand castings with abrasive surface inclusions are cut with one of three types of rotary-cut broaches (Fig. 17). The design concept is similar to that of a chip-breaking slot; but the cutting edge has been drastically reduced, and the slots between the teeth have become much deeper. Rotary-cut broaching teeth are heavier to withstand the heavy cutting load and are spaced in staggered fashion along the axis of the broach to generate the entire circumference of the hole. The tools are designed to take deep cuts underneath a poor-quality surface. Once this surface has been penetrated, the balance of the broaching tool proceeds to semifinish and finish the underlying metal in the normal manner. Fig. 17 Three types of rotary- cut broaching tools designed to penetrate rough skins, as on castings and forgings, without exceeding the power ratings of a broaching machine. (a) Hexag onal rotary cut. (b) Radial rotary cut. (c) Spline rotary cut The hexagonal rotary-cut broach (Fig. 17a), used for small-diameter holes, removes little stock. Depth of cut is limited to the distance across the flats. The radial rotary-cut broach (Fig. 17b) removes more stock than the hexagonal tool because the cutting portions of the teeth are connected by arcs rather than by flats. Spline rotary-cut broaches (Fig. 17c) offer a greater degree of flexibility than either of the other tool types and also permit maximum stock removal. The amount of stock removal is primarily governed by the capacity of the broaching machine rather than by any tooling limitations. Rise per tooth may be as much as 1.3 mm (0.050 in.) on such broaches. In addition to the typical broaches shown in Fig. 16 and 17, many special designs are used for performing more complex operations. Two surfaces on opposite sides of a casting or forging are sometimes machined simultaneously by twin broaches, and in other cases, three or four broaches are drawn through a part at the same time for finishing as many duplicate holes or surfaces. Progressive Broaches. Notable developments have been made in the design of broaches for external broaching. One of these developments is the progressive broach (Fig. 18). Employed primarily for broaching wide, flat surfaces, the first few teeth in progressive sectional broaches completely machine the center, while succeeding teeth are offset in two groups to complete the remainder of the surface. Fig. 18 One-piece (a) and sectional (b) progressive broaches. Top and side views of both types are shown. One-piece progressive broaches (Fig. 18a) have two sets of narrow roughing teeth, with each set positioned at an angle with respect to the centerline of the broach holder, thus forming an inverted vee. Each tooth or insert takes a shear cut, generally to full depth, but covers only a small portion of the workpiece surface. This is similar to a single-point tool on a shaper or planer progressively generating a flat surface on the workpiece. Full-width teeth for semifinishing and finishing are located behind the roughing teeth on progressive broaches so that the entire surface is cut in one pass. For narrow surfaces, the teeth or inserts at the starting end are V-shaped. On subsequent teeth, the vees gradually widen until the full required width of the surface is cut. The final teeth are flat, similar to those on a slab broach. Pull broaches, as the name implies, are pulled through or against the surface of the workpiece. Most internal broaching is done with pull broaches. Because there is no problem of bending, pull broaches can be longer than push broaches for the same size of hole, and they can also remove more stock in one pass. Pull broaches can be made to long lengths, but cost usually limits the length of solid pull broaches to approximately 2.1 m (7 ft). Broaches longer than 2.1 m (7 ft) are usually made up of sections similar to shell broaches because the cost is less for replacing a damaged or worn section than for replacing the entire broach. Push broaches, for internal broaching, are necessarily shorter than pull broaches because of the problem of bending under load. Push broaches are used for broaching blind holes (Fig. 6) or for multiple-station broaching machines in which several short broaches, rather than a single long broach, are used to reduce the time required for a given operation. Broach Tool Materials Hardened high-speed tool steel is by far the most widely used material for solid broaches or for the cutting teeth of other types of broaches. The tools are usually ground to final dimensions after hardening. The grade of high-speed tool steel is normally chosen on the basis of minimum overall cost, balancing tool life and production rate against tool cost (material, heat treatment, fabrication, and regrinding for reuse). High-Speed Tool Steels. In the early stages of broaching technology, broach tools were made from water-hardening tool steels. These tools were used on slow, screw-type broaching machines. With the introduction of new machines with higher speeds and greater production rates, high-speed tool steels became the principal materials for broach tooling. The following is a list of typical tool steels and the materials that are commonly broached with these steels: • M2 tool steel: General use, including brass, aluminum, magnesium, and the following steels: 1020, 1063, 1112, 1340, 1345, B- 1113, 4140, 4340, 5140, 8620 (26 HRC), type 347 stainless steel, and type 416 stainless steel (35 to 40 HRC) • M3 tool steel: Aluminum castings, cast irons, A-286 (32 to 3 8 HRC), Greek Ascoloy (32 to 38 HRC), M-252, D- 979 (40 HRC), and the following steels: 4140 (32 HRC), 4337 (29 to 23 HRC), 4340 (32 to 38 HRC), 8617 (30 to 36 HRC), 8620 (32 HRC), 9310 (36 to 38 HRC), 9840 (32 to 36 HRC), type 403 stainless (37 to 40 HRC) • M4 (or T5) tool steel: Cast irons • T2 tool steel: Steels: 1112, 4340 (35 to 40 HRC), type 403 stainless (30 to 35 HRC); titanium alloys, PWA-682 Ti (36 HRC), Lapelloy (30 to 35 HRC), Greek Ascoloy (32 to 38 HRC), 19- 9DL (20 to 27 HRC), and Discalloy (23 to 32 HRC) • T5 tool steel: A-286 (29 HRC), Chromalloy (30 to 35 HRC), Incoloy 901, and PWA- 682 Ti (34 to 36 HRC) • T15 tool steel: Aluminum 2219, A-286 (32 to 36 HRC), Stellite, 17-22 A(S) (29 to 34 HRC), N- 155 (30 to 40 HRC), AMS 4925 titanium (32 to 40 HRC ), Waspaloy, Incoloy 901 (32 to 36 HRC), and the following steels: heat- resistant steels, conventional alloy steel forgings, 4340 (35 to 40 HRC), 52100, 9310 (26 to 30 HRC), and 17-4PH Carbide-Tip Cutters. Most of the carbide cutters used to broach cast iron are used in flat surface broaching applications, although contoured cast iron surfaces have been broached successfully. Surface broaching of pine-tree slots has been attempted with carbides on high-temperature alloy turbine wheels, but with little success. The carbide edges tend to chip on the first stroke. Carbide-tip broaches are seldom used on conventional steel parts and forgings. One reason is that good performance is obtained from high-speed steel tools; another is that the low cutting speeds of most broaching operations (from 3.7 to 9 m/min, or 12 to 30 sfm) do not lend themselves to the advantages of carbide tooling. The success of carbide tooling on cast irons is due to the resistance of carbide to abrasion on the tool flank below the cutting edge. Another problem with carbide-tip tools is that a broaching machine work fixture must be exceptionally rigid to prevent chipping of the cutting edge. Experimental work with extra-rigid tools and workpiece fixtures, however, has shown that tool life and surface finish can be greatly improved with carbide-tip tools, even when used on alloy steel forgings. Cast high-speed tool steels are seldom used in broaches. One property of the cast tool materials that prohibits their use in monolithic internal pull broaches is low tensile strength. Most cast alloys that can attain a hardness of 60 HRC or higher do not have ultimate tensile strengths much in excess of 585 MPa (85 ksi). To provide the optimum combination of abrasion resistance and toughness, broach cutting teeth are normally hardened to 64 to 66 HRC for the general-purpose grade, ranging upward for the more highly alloyed grades to a maximum of 66 to 68 HRC for T15. For longer tool life, surface treatments such as nitriding or oxidizing are sometimes employed. Nitriding increases superficial hardness, and both nitriding and oxidizing minimize sticking or welding of the tool to the work material. Chromium plating will also minimize sticking, although this plating is prone to chipping. Carbide inserts or rings are used to a limited extent in internal broaching, primarily on small parts made of free-machining materials such as gray iron, usually in applications requiring extremely close tolerances at high production rates. Broaching of steel castings, in which a carbide tool can cut through local hard spots with less tool damage than high- speed tool steel, is another application of carbide inserts. Broach Design Basic broach design is shown in Fig. 13, which presents the dimensional details of a typical pull broach for producing a round hole. This broach has been used for the production broaching of a hole 25.36/25.31 mm (0.9985/0.9965 in.) in diameter in a normalized forged steel steering knuckle. A starting hole 23.8 mm ( in.) in diameter was drilled through the forging to accommodate the broach. As shown in Fig. 13, the first cutting tooth of this broach is 23.6 mm (0.930 in.) in diameter, and each tooth in the roughing section increases 0.0475 mm (0.00187 in.) in diameter over the one preceding it (the first three or four teeth may cut little or nothing, depending on the exact size of the drilled hole). Thus, as the broach is pulled through the workpiece, cutting begins gradually, and as each succeeding tooth engages the work, it removes a small amount of metal. The progressive increase in tool diameter is usually greatest in the roughing section. In this broach, the increase is 0.0475 mm (0.00187 in.) for the roughing teeth, 0.013 mm (0.0005 in.) for the first four teeth in the intermediate section, and 0.0065 mm (0.00025 in.) for the remaining teeth in the intermediate section. In the finishing section, all teeth are 25.36 mm (0.9985 in.) in diameter the maximum permissible diameter of the broached hole. Tooth contours are shown in the upper left corner of Fig. 13. The greater depth of the gullet and the greater pitch for teeth 1 through 36 permit better chip accommodation. This is essential, because these teeth make the greatest advance and therefore remove the most metal. The pitch length (distance between teeth) in both the roughing and the intermediate sections is staggered to prevent chatter as the broach is pulled through the work. Chip breakers (discussed in the section "Chip Breakers" in this article) are incorporated in the roughing teeth and the first four intermediate teeth, as specified in the notes in Fig. 13. The chip breakers are staggered from tooth to tooth so that the ridges left in the workpiece surface by the discontinuities in any one tooth are removed by the tooth that follows. (Note that the last three intermediate teeth have no chip breakers, so that these teeth can remove all traces of irregularities left by chip-breakers on preceding teeth before the first finishing tooth starts cutting.) Face (hook) angles for broach teeth are selected on the basis of hardness and ductility of the work metal. Metals that yield brittle chips, such as cast iron or leaded brasses, are usually cut most efficiently by teeth with a narrow face angle. Ductile materials, such as annealed or normalized steels, usually respond better to wider face angles. Face angles on broaches are similar to top rake angles on single-point tools. Recommended face angles, along with backoff angles, for various metals are given in Table 2. Table 2 Typical broach face and backoff angles Material Face angle, degrees Backoff angle, degrees Aluminum 6-10 . . . Babbitt 8-10 . . . Brass -5 to 5 2-3 Bronze 0 -2 Cast iron 6-10 2-5 Copper 15 2-3 Zinc 6 . . . Aluminum bronze 15 2-3 SAE 1037 15 1-2 SAE 1112 15 2 SAE B-1113 15 2-3 SAE 1340 12 1-2 SAE 4140 8-15 1-3 SAE 4337 8-15 1-3 SAE 5140 15 1-2 SAE 5140 (Type 410 stainless) 18 (roughing) 20 (finishing) 2 2 SAE 9310 18 (roughing) 20 (finishing) 2 2 Type 303 stainless steel 15 -2 Type 304 stainless steel 15 -2 Type 403 stainless steel 15-20 (roughing) 30 (finishing) 3 5 Type 431 stainless steel Up to 28 . . . M-308 15 3 N-155 20 2 Greek Ascoloy 15 2-3 Chromalloy 15 2 Lapelloy 12-15 2 A-286 10-15 (roughing) 15-18 (finishing) 2-3 René 41 15 3 Incoloy 901 15 (roughing) 18 (finishing) 3 Titanium 140A 5-15 2-4 Titanium 150A 5-9 2-5 Titanium PWA A682 12-15 (roughing) 15 (finishing) 3 3 Source: Metalcutting: Today's Techniques for Engineers and Shop Personnel. McGraw-Hill, 1979 When broaching similar parts of different metals, a different face angle must often be used for each of the metals cut. Gullets. The shape of the gullets (chip spaces) of broach teeth influences the efficiency of the broaching operation and has a marked effect on broach life. To obtain maximum efficiency, it may be necessary when sharpening a broach to deviate from conventional gullet shape, as in the following example: Example 1: Gullet Redesign for Increased Broach Life. Figure 19 shows original and revised designs of the gullet in teeth of a broach used for cutting fir-tree slots in a turbine wheel of Incoloy 901. The original full-radius design encourages the packing of chips in the gullet so tightly that they were almost impossible to remove by wire brushing. The broach became overheated because of the transfer of heat from the packed-in chips. At times, the packing of chips in the gullet caused galling and tears in the broached surface of the workpiece. Fig. 19 Revision of gullet configuration to eliminate problems in broaching Incoloy 901. Dimensions given in inches When the gullet was ground to the two-angle configuration shown as the improved design in Fig. 19, broach life increased from one piece per grind to three pieces per grind, and galling and tearing of the broached surface were eliminated. The change of gullet had no effect on the number of resharpenings; broaches could still be reground seven or eight times. Chamfered Edges. The sides of broach teeth used for forming configurations such as keyways or fir-tree slots are usually chamfered to prolong tool life. The need for chamfered teeth increases as the Machinability of the work metal decreases. The amount of chamfer may be restricted by the shape being broached, but even as little as 0.13 mm (0.005 in.) chamfer is helpful. The following example demonstrates the beneficial effect of tooth chamfer in the broaching of heat-resistant alloys. Example 2: Addition of Chamfer to Prolong Tool Life When in Turbine Wheels. A cross section of one of 102 fir-tree slots that were broached around the periphery of an aircraft engine turbine wheel made of Incoloy 901 is shown in Fig. 20. The broach was made of T15 high-speed tool steel and was heat treated to 66 to 68 HRC. The wheels were broached in a 760 kN (85 tonf) vertical machine with a 2290 mm (90 in.) stroke at a speed of 3050 mm/min (120 in./min). A broaching oil having a viscosity of 155 Saybolt Universal seconds (SUS) at 40 °C (100 °F), 2% fat content, 0.8% active sulfur, and 2.1% Cl was used. Fig. 20 Addition of chamfer to corners of broach teeth for increased tool life in the broaching of fir- tree slots in a turbine wheel Before a chamfer was added to the broach teeth (shown at bottom, Fig. 20), broach life was 19.2 wheels, and an average of two wheels could be broached between sharpenings. The addition of this 0.13 mm (0.005 in.) by 45° chamfer parallel to the broaching axis on the sharp corners of the teeth increased broach life to an average of 24.8 wheels and increased to three the number of wheels that could be broached between sharpenings. The improvement in broach life was assisted by improved grinding and resharpening procedures and by more careful handling of the broach. Effect of Tooth Design on Chatter. When chatter develops in broaching, loss of accuracy, poor surface finish on the workpiece, and excessive broach wear are probable results. With extreme chatter, the broach is likely to break. In broaching, cuts are often interrupted, depending on the length of the section to be broached and the distance between successive cutting teeth. In general, the likelihood of chatter increases as the severity of the interruptions in cutting increases. Conventional broaches having circular teeth such as those shown in Fig. 1 and 13 are more susceptible to chatter than specially designed broaches because there is a complete interruption after each cutting tooth. Either of two approaches is frequently used in broach design to minimize interrupted cutting and chatter: • In broaching flat surfaces or several internal splines spaced around a periphery, tee th staggered longitudinally provide a more uniform cutting action • When broaching round holes, a broach having helical teeth is an effective means of eliminating chatter Specially designed broaches are more expensive than conventional types, but the increased broach cost is often justified. Chip Breakers Chip control is essential in all machining operations, but especially in broaching. In single-point machining such as lathe turning, the chip leaves the cutter as soon as it is formed. In broaching, however, the chip stays in the gullet, or chip space, behind each tooth until that tooth clears the workpiece. Chip space is limited by the pitch of the teeth, and in small broaches by the root diameter of the broach. Thus, it is seldom possible to provide enough space for chips, particularly in small-diameter broaches. In broaching, therefore, chips must be controlled to keep chip-space requirements to a minimum and to facilitate chip removal. Broaches are provided with chip breakers, which are small grooves or notches approximately 0.8 to 2.4 mm ( to in.) wide that transversely break the cutting edge and land of each roughing and semifinishing tooth (Fig. 21). These grooves break the continuity of the width of the chip. Thus, instead of one wide chip, several narrow chips are formed. These narrow chips are easily washed out by the cutting fluid, are brushed out, or fall away when the gullet clears the workpiece. Fig. 21 Chip breakers on a flat broach (a) and a round broach (b). Notches that split the heavy chips can be either U-shaped or V-shaped breakers. Broaches that cut around holes especially require chip breakers. Without chip breakers, the chips would be continuous rings that would be difficult to remove from the broach. In addition, the shape of the chips must permit them to drop into the chip space behind each tooth. Chip breakers accomplish this by making smaller chips. Chip breakers are staggered from tooth to tooth so that the ridge left by the chip breaker in one tooth is removed by the tooth immediately following. Generally, finishing teeth have no chip breakers, although some broaches require them in the first few teeth. Fixtures In broaching, as in other machining operations, fixturing of the workpiece is required. Broaching fixtures have several functions. They must locate the workpiece accurately and hold it securely. For certain applications, such as broaching helical gears, the fixture must position the part accurately and firmly, yet permit the part to rotate as required. Fixtures can be used to carry workpieces in and out of the broaching position or to carry them from one broaching position to another where more than one broach is required. Fixtures can also be used to guide the broach when it moves over or through the workpiece. Fixtures used in broaching must not obstruct the removal of chips. Broaching fixtures must provide more holding force and more rigidity and support than fixtures for most other machining operations because more teeth are cutting at any one time than is typical for other operations. Broaching fixtures can be manual, semiautomatic, or automatic. Cost considerations and the quality of parts to be broached will largely determine the type of fixture used. Semiautomatic and automatic fixtures can be operated pneumatically, hydraulically, or mechanically. [...]... cast iron KP-7 cast iron G E I H H I I I I A I G I J A A I D D I I E E C C C C D B B 70 HRB 70 HRB 3 6-3 8 32 3 2-3 6 3 2-3 8 85 HRB 29 2 0-2 8 2 8- 3 0 3 0-3 5 3 2-3 8 2 3-3 0 20 3 6-3 8 2 9-3 4 3 5-4 0 3 2-3 6 32 2 5-2 9 38 2 4-2 8 4 0-4 7 3 2-3 6 4 0-4 2 28 3 8- 4 0 3 2-3 6 3 6-3 8 3 1-3 2 3 4-3 6 3 0-3 7 85 HRB 8 0 -8 5 HRB 3 7-4 0 60 3-1 2 1 5-2 0 2 4-3 1 1 2-1 8 5-1 0 87 HRB 1 3-1 8 1 5-2 0 8- 1 5 8- 1 5 25 90 HRB Tolerance mm in 0.05 0.002 0.0 58 0.0023 0.019... 0 .89 0 .80 0 .8 0-1 .00 1.60 1.60 1.50 1.25 1.60 0 .8 0-1 .60 1.1 4-1 .60 0 .80 0.75 1.60 0 .80 1. 0-1 .5 1.50 1.60 0 .80 0 .80 0 .80 0 .80 1.60 1.60 1.60 0.75 1.5 5-2 .05 1.60 0.6 3-1 .5 0.7 1-1 .5 1. 0-1 .15 1.2 5-2 .5 1. 5-2 .0 1. 5-2 .0 0.75 2. 0-2 .5 3.20 in 3 2-4 5 32 2 4-3 2 80 63 3 5-4 2 80 32 32 63 32 35 32 3 2-4 0 63 63 60 50 63 3 2-6 3 4 5-6 3 32 30 63 32 4 0-6 0 60 63 32 32 32 32 63 63 63 30 6 0 -8 0 30 2 5-6 0 2 8- 6 0 4 0-4 5 5 0-1 00 6 0 -8 0... results Metal Heat treatment(a) Hardness, HRC 26 1 8- T61 Al 2014-T6 Al Ti-6Al-4V Stellite 31 SAE 51410 (type 410SS) Greek Ascoloy Inconel Inconel X Timken 1 6- 2 5-6 A- 286 G G E B H I A H F G S- 81 6 SAE 3310 SAE 9310 1 7-2 2A(S) 1 7-2 2A SAE 984 0 SAE 4130 SAE 4140 SAE 4340 M2 tool steel EMS 544 Inconel 901 René 41 WAD 782 3A D-979 EMS 73030 M-3 08 Chromoloy PWA- 682 (Ti) Lapelloy Type 303 SS Type 304 SS Type 403... S4,S2 M2, M7 3 10 0.05 0.002 S9, S11(a) T15, M42(a) 13 5-1 85 Annealed 6 20 0.075 0.003 13 5-1 85 Annealed 6 20 0.075 0.003 22 5-2 75 Cold drawn 5 15 0.075 0.003 13 5-1 75 Annealed 7.5 25 0.10 0.004 S4, S2 S4, S2 S9, S11(a) S4, M2, M7 M2, M7 T15, M42(a) M2, 15 0-2 00 17 5-2 25 20 0-2 50 8 5-1 25 22 5-2 75 12 5-1 75 32 5-3 75 12 5-1 75 32 5-3 75 17 5-2 25 32 5-3 75 17 5-2 25 32 5-3 75 Wrought stainless steels Ferritic: 405, 409, 429,... 305, 3 08, 321, 347, 3 48, 384 , 385 Martensitic: 403, 410, 420, 422, 501, 502 in./tooth M2, M7 M2, M7 M2, M7 10 0-1 50 Wrought alloy steels Low carbon: 4012, 4023, 4024, 41 18, 4320, 4419, 4422, 4615, 4617, 4620, 4621, 47 18, 4720, 481 5, 481 7, 482 0, 5015, 5115, 5120, 61 18, 81 15, 86 17, 86 20, 86 22, 88 22, 9310, 94B15, 94B17 Medium carbon: 1330, 1335, 1340, 1345, 4027, 40 28, 4032, 4037, 4042, 5155, 5160 , 51B60,... 5155, 5160 , 51B60, 6150, 81 B45, 86 25, 4047, 4130, 4135, 4137, 4140, 4142, 4145, 4147, 4150, 86 27, 86 30, 86 37, 86 40, 86 42, 86 45, 4161 , 4340, 4427, 4626, 50B40, 50B44, 5046, 50B46, 50B50, 86 B45, 86 50, 86 55, 86 60, 87 40, 87 42, 5060, 50B60, 5130, 5132, 5135, 5140, 5145, 5147, 5150, 9254, 9255, 9260, 94B30, High carbon: 50100, 51100, 52100, M-50 mm/tooth S4, S2 S4, S2 S4, S2 32 5-3 75 Wrought carbon steels... 0.00 08 0.025 0.001 0.0 38 0.0015 0.060 0.0024 0.0076 0.0003 0.013 0.0005 0.071 0.00 28 0.060 0.0024 0.10 0.004 0.025 0.001 0.20 0.0 08 0.025 0.001 0.05 0.002 0.015 0.006 0.025 0.001 0.05 0.002 0.0076 0.0003 0.013 0.0005 0.10 0.004 0.05 0.002 0.025 0.001 0.075 0.003 0.05 0.002 0.05 0.002 0.013 0.0005 0.075 0.003 0.013 0.0005 Finish m 0 .8 0-1 .15 0 .80 0.6 1-0 .80 2.00 1.60 0 .8 9-1 .07 2.00 0 .80 0 .8 0-1 .60 0 .80 ... various steels with high-speed tool steels and carbide tools Material Hardness, HB Condition Speed Chip load m/min Wrought free -machining carbon steels Low-carbon resulfurized: 11 08, 1109, 1110, 1115, 1 116, 1117, 11 18, 1119, 1211, 1212, 1213, 1215 Medium-carbon resulfurized: 1132, 1137, 1139, 1140, 1141, 1144, 1145, 1146, 1151 Low-carbon leaded: 10L 18, 11L17, 12L13, 12L14, 12L15 10 0-1 50 Hot rolled or annealed... cut mm in 34.92 1.375 15.37 0.605 38. 1 1.50 Shape broached Square Spline Serrations Pieces broached per hour 5 0-7 0 9 0-1 20 6 0-9 0 Pieces per sharpening 2500 4000 1500 Total pieces per broach 48, 000 36,000 28, 500 Effect of Carbon Content Low-carbon steels ( . 2 0-2 8 0.025 0.001 0 .8 0-1 .60 32 63 2 8- 3 0 0.060 0.0024 0 .80 32 3 0-3 5 0.025 0.001 0 .89 35 A- 286 G 3 2-3 8 0.015 0.0006 0 .80 32 S- 81 6 G 2 3-3 0 0.025 0.001 0 .8 0-1 .00 3 2-4 0 SAE 3310 E 20. 26 1 8- T61 Al G 70 HRB 0.05 0.002 0 .8 0-1 .15 3 2-4 5 2014-T6 Al G 70 HRB 0.0 58 0.0023 0 .80 32 Ti-6Al-4V E 3 6-3 8 0.019 0.00075 0.6 1-0 .80 2 4-3 2 Stellite 31 B 32 0.05 0.002 2.00 80 SAE. 63 M-3 08 . . . 3 6-3 8 0.060 0.0024 0 .80 32 Chromoloy . . . 3 1-3 2 0.10 0.004 0 .80 32 PWA- 682 (Ti) . . . 3 4-3 6 0.025 0.001 0 .80 32 Lapelloy J 3 0-3 7 0.20 0.0 08 0 .80 32 Type 303 SS A 85 HRB