Volume 16 - Machining Part 7 pdf

When a center hole is unobjectionable, the trepanning tool consists of an adjustable fly cutter mounted on a twist drill (Fig. 1); the drill serves as both driver and pilot, and the single-point tool can be positioned as desired to change the size of the circle cut. If a center hole cannot be permitted, a tool of the type shown in Fig. 1 can be used without a drill pilot. By this technique, however, rigidity is more difficult to maintain, and there is greater likelihood of tool chatter and loss of dimensional control. Fig. 1 Drill- mounted adjustable fly cutter used for trepanning various sizes of disks from flat stock, or grooves around centers There is no established maximum thickness or diameter of disks that can be cut by this method of trepanning. Because of the load imposed on the tool, however, the process is seldom used for cutting material more than about 6.4 mm ( in.) thick. In addition, because rigidity decreases as diameter increases, disks cut by this method are usually less than 150 mm (6 in.) in diameter. Larger cuts by trepanning are not made if other methods can be used. Smaller trepanning cuts may compete with press-working (if the means are available), and larger cuts may compete with other methods, such as flame cutting. In this type of trepanning, slow speeds (ranging downward from about 10 m/min, or 35 sfm) are ordinarily used and feed is controlled manually. Cutting fluids are seldom employed. Large Shallow Through Holes Round through holes having diameters that exceed depth by a factor of about five or more can often be efficiently and accurately produced by trepanning. Workpiece configuration often dictates the trepanning technique used because special fixturing may be necessary to ensure adequate rigidity. The tools and techniques employed in one application are described in the following example, in which trepanning was preferred to drilling. Example 1: Nine Shallow Holes in Web of a Steel Gear. Trepanning proved more practical than drilling for producing nine weight-reducing holes in the web section of an aircraft accessory drive gear made of 9310 steel (Fig. 2). Depending on the size of these gears, the holes ranged from 19 to 32 mm ( to 1 in.) in diameter, and web-section thickness ranged from 3.56 to 6.35 mm (0.140 to 0.250 in.). Fig. 2 Shallow holes produced by trepanning in aircraft gear shown at top left. Top-brazed carbide insert s cut only 40% as many holes per grind as side-brazed inserts. Trepanning was done with carbide-insert single-point tools at a speed of 91 m/min (300 sfm) and a feed of 0.05 mm/rev (0.002 in./rev). Originally, a top-brazed insert (bottom left, Fig. 2) was used, but tool life was only 30 holes per grind. By changing to side-brazed inserts (bottom right, Fig. 2), tool life was increased to 75 holes per grind. With either tool, maximum tool life was obtained when the tool was not allowed to cut completely through the web. A thin section was left to hold the plug, and this section was easily knocked out during indexing of the gear. Circular Grooves The tools and techniques used for producing round disks or large shallow through holes can also be used to provide metal parts with circular grooves for accommodating O-rings or for other purposes. The only difference is that the cutter must be shaped to form the desired cross-sectional shape of the groove. When a groove to be cut is only slightly larger in diameter than a concentric pilot hole, optimum results are obtained by the use of a combination drilling-and-trepanning tool that resembles a hollow mill (Fig. 3). With this tool, a twist drill is inserted into a hollow cutter and held by a setscrew. This type of trepanning cutter usually has two or more cutting edges to provide balance, which assists in maintaining dimensional control. Cutting edges have a back rake angle of about 20° for most applications. Fig. 3 Combination tool for producing a groove close to a concentric pilot hole Any machines normally used for drilling are suitable for driving combination tools of the type shown in Fig. 3. Speeds up to 30 m/ min (100 sfm) are ordinarily used, in conjunction with feeds of about 0.1 mm/rev (0.004 in./rev). Soluble oils are usually satisfactory as cutting fluids, although sulfurized oils are preferred when tolerance and finish requirements are critical. The following example describes an application in which trepanning was more efficient and economical than the use of single-point tools for producing a circular face groove. Example 2: Trepanning Versus Single-Point Plunge Cutting. Originally, the 73 mm (2 in.) groove in the 4140 steel part shown in Fig. 4 was produced in roughing and finishing operations on a lathe, using single-point carbide-insert tools. Chip build-up and tool breakage were continual problems. Tool life per sharpening was only 25 pieces, and production time per piece was 3.9 min. Fig. 4 Tool used in trepanning o peration (shown at top left and bottom). The part is shown at top right. Dimensions given in inches Tool breakage and chip buildup were eliminated (and grooving was reduced to a one-operation job) by substituting trepanning for the original method. The trepanning tool used had two carbide cutters mounted on an 1141 steel body; tool design is shown in Fig. 4. Trepanning also reduced time per piece to 1.8 min (less than half, compared with the original method) and doubled tool life to 50 pieces per sharpening. Deep Holes Trepanning is often the most practical method of machining deep holes or tubes from the solid. Deep-hole Trepanning is similar to gun drilling (see the article "Drilling" in this Volume) in that both processes require a pressurized cutting fluid system and employ self-piloting cutting action. The two main differences are: • Trepanning is practical only for larger holes (more than about 50 mm, or 2 in., in diameter) • Trepanning produces a solid core, while gun drilling forms only chips As a means of producing holes 50 mm (2 in.) in diameter or larger (especially holes whose depth is eight or more diameters), Trepanning offers the following advantages over spade or twist drilling, with their allied operations: • Closer tolerances can be met on diameter and straightness • Drilling of deeper holes is feasible • Rate of metal removal is higher • In machining costly work materials, cores are more valuable than chips Trepanning can also be used to produce a tube from a cylindrical billet when machining space-age metals such as beryllium. The trepanning of a cylindrical core from the center of a solid cylinder of metal is not ordinarily done in regular mass production. Beryllium, however, is a problem metal that needs special methods. Misalignment is probably the most frequent single source of difficulty in deep-hole trepanning. The misalignment may be caused by insufficient rigidity in the tooling and the setup. Accurate alignment and rigidity are essential for control of dimensions and finish and for satisfactory tool life at high depth-to-diameter ratios. Machines for Deep-Hole Trepanning For trepanning holes less than about five diameters deep, simple vertical drill presses are usually satisfactory. However, as the depth of the hole exceeds five times diameter, any type of vertical equipment becomes progressively more impractical. In addition, as the depth-to-diameter ratio increases, accuracy is lost more rapidly in equipment in which the tool is rotated and the work is held stationary. Therefore, engine lathes, turret lathes, or horizontal drilling machines are preferred for Trepanning deep holes. In all of these machines, the workpiece is rotated while the tool remains stationary. This technique results in greater accuracy, other conditions being constant. Regardless of the type of machine used, it must be rigid and capable of speeds up to 185 m/min (600 sfm) to accommodate carbide tooling. It should also have variable feed control. Engine Lathes. Figure 5 shows a basic engine lathe setup, in which a cylindrical workpiece is rotated, the tool is fed into it, and an inside-diameter-exhaust trepanning head is used (see the section "Tools for Deep-Hole Trepanning" in this article). Such a setup is used for holes about 50 to 115 mm (2 to 4 in.) in diameter. One end of the workpiece is held in a three-jaw chuck, and the other end in a roller steady rest (rollers are about 150 mm, or 6 in., in diameter). A relatively long workpiece requires an additional steady rest midway between the chucking headstock and the roller steady rest. Fig. 5 Engine lathe setup for trepanning deep holes The end of the workpiece next to the steady rest must be faced at right angles to the spindle centerline. The facing cut, made by a tool on a cross slide, provides a flat surface for the fluid seal on the guide bushing and prevents the runout that could make the fluid seal leak. The guide bushing should be mounted on ball bearings which are the most economical means of support at the speeds involved. Cutting fluid under pressure enters the leakproof rotary joint behind the bushing and flows into the annular space around the hollow boring bar. The fluid then flows to the cut between the bushing and the periphery of the tool head, picks up the chips, and flushes them through the head between the cutter and the core and then out along the space between the core and the inner wall of the boring bar. An additional fluid seal is necessary at the rear of the guide-bushing/fluid-transfer unit. The tailstock end of the boring bar is mounted in a headstock on the lathe carriage and is rigidly clamped in position by means of a bearing cap and clamping nuts. To serve as a vibration damper, a steady rest is located directly behind the guide-bushing/fluid-transfer unit. This damper is of the same construction as the boring-bar headstock, except that a two-piece bronze bushing is used to damp vibration and to allow the boring bar to slide. Alignment is critical. The spindle, chuck, steady rests, guide bushing, and boring-bar headstock must be as nearly in line as possible. In addition, the machine ways must be aligned, and the boring bar must be ground to uniform diameter and straightness. The bores in the guide-bushing/fluid-transfer unit, the vibration-damper unit, and the boring-bar headstock should be large enough to accommodate the boring bar for the largest-diameter hole to be trepanned on the machine. For smaller holes, smaller boring bars can be used with appropriate bushings. For holes more than about 115 mm (4 in.) in diameter, other setups are sometimes more economical and can be used with an outside-diameter-exhaust head for trepanning relatively deep holes (see the section "Tools for Deep-Hole Trepanning" in this article). One of these adaptations is the use of a three-roll support on the bed of an engine lathe. A three-roll support used in conjunction with an outside-diameter-exhaust head effects a savings by eliminating the need for a starting or guide bushing. Turret lathes are also suitable for trepanning relatively deep holes, as indicated in the following example. Example 3: Use of a Turret Lathe for Trepanning. Holes 127 mm (5 in.) in diameter and 915 mm (36 in.) deep were trepanned in vacuum-melted 4340 steel using an outside-diameter-exhaust trepanning head with a 19 mm ( in.) wide carbide cutting tip. A turret lathe of 11 kW (15 hp) capacity was used to rotate the workpieces at 190 rev/min (76 m/min, or 250 sfm).Water-soluble oil, under pressure of 275 kPa (40 psi) was pumped through the cutting area at 190 L/min (50 gal./min). At a feed rate of 0.18 mm/rev (0.007 in./rev), two pieces per hour were produced. Tools for Deep-Hole Trepanning Boring bars for trepanning are hollow tubes that allow the workpiece core to enter with enough clearance for cutting fluid to flow to the cutter or for fluid and chips to be forcibly exhausted from the cutter. The bar is usually made from 52100 bearing steel or a similar steel. Wall thickness ranges upward from about 7.9 MM ( in.) depending on the length of the bar and the required resistance to torsional forces. Trepanning heads are cylindrical and usually employ a single solid-carbide or carbide tip cutter. Multiple-cutter heads, despite their desirable chip-breaking action, are used to a lesser extent because they pose problems in attaining balanced cutting action without which hole accuracy may be sacrificed. Single-cutter heads (Fig. 6) are self-piloting; they are supported and guided by wear pads located about 90 and 180 ° behind the cutter. The head fits onto the boring bar by means of a pilot diameter and can be driven by three lugs. With this mating design, the head is locked to the bar screws. Some heads are secured to the bar by Acme threads around the inner circumference of the head, but high torsional forces can cause thread seizure. Ahead of the cutting edge on the outside diameter of the head is a relief for intake of cutting fluid or for exhaust of cutting fluid and chips. Fig. 6 Two types of single-cutter trepanning heads One type of head (Fig. 6a), usually for holes up to 115 mm (4 in.) in diameter and with depths of 12 to 15 diameters, accommodates cutting fluid flow from the inside diameter of the bar and exhausts the fluid on the outside diameter. Recommended maximum depths for holes trepanned with outside-diameter-exhaust heads are as follows: Diameter Depth mm in. mm in. 50-64 2-2 610-762 24-30 65-89 2 -3 762-1065 30-42 90-115 3 -4 1065-1780 42-70 For holes 116 mm (4 in.) in diameter and larger, maximum depth is limited only by machine design. With this type of head, chips and fluid are exhausted along a longitudinal groove milled on the outside diameter of the head. The clearance between the core and the inside wall of the head must be controlled so that the volume of cutting fluid is restricted. As a result, there is a high-velocity centrifugal action that forces the chips away from the cutting edge. In production trepanning, one plant found that a fluid-inlet area of 645 mm 2 (1 in. 2 ) produces a pressure of about 345 kPa (50 psi) on a 178 mm (7 in.) diam head. This size of inlet area allows full pump flow through the head and provides sufficient velocity for chip disposal. As the hole size decreases and the inlet area remains constant, the pressure increases. Increased pressure is desirable as hole diameter decreases or as depth increases. For holes less than 100 mm (4 in.) in diameter, however, an inlet area of 645 mm 2 (1 in. 2 ) is not possible; for these holes, the inlet area should be made as large as possible to provide adequate volume without weakening the head. The outside diameter of an outside-diameter-exhaust head is only 0.50 to 0.64 mm (0.020 to 0.025 in.) smaller than the diameter of the hole being cut; this prevents chips from escaping between the head and the wall of the hole. As a result, the possibility of a marred finish is lessened, and channeling of the fluid and chips through the exhaust groove is facilitated. To minimize the problem of chip disposal in holes more than about 15 diameters deep, an inside-diameter-exhaust head (Fig. 6b) is used. With this type of head, fluid under pressure flows to the cutting edge over the outside diameter of the bar and head. The fluid and the chips are exhausted through the inside diameter of the boring bar. Wear pads (Fig. 6) are essential components of single-cutter heads. Wear pads balance cutting force, control hole size, and provide a burnishing action that may improve finish. Ordinarily, wear pads have steel bodies and brazed-on carbide wearing surfaces. The wear pad body may have two angular sides that result in a dovetail fit in the head.The pads are circle ground so that when they are positioned in the head they will clear the bore wall by about 0.05 mm (0.002 in.) and will project about 0.25 mm (0.010 in.) from the head. One pad is located approximately 90° behind the cutting edge; this pad steadies the head against the bore and balances the cutting force. The other pad is about 180° behind the cutter and automatically controls the size of the hole. If the cut is oversize, the bore is large, and the pressure on this pad is immediately decreased. As a result, the head moves away from the surface being cut, reducing the bore size until equilibrium is again established. Similarly, if the cut is undersize, pressure on the pad is increased, and the head moves toward the surface being cut. Initial cutting action is controlled by a guide bushing (Fig. 5), by a counterbore, or by a starting tool that cuts a groove (Fig. 7).If a bushing is used, starting feeds are relatively light and characteristically produce stringy chips, which must be removed at intervals. The counterbored hole or starting groove should be deep enough to ensure self-piloting by the trepanning head. Fig. 7 Starting tool for trepanning Conventional cutters (Fig. 8) have a carbide tip brazed on a tool steel body. (Because index positions are limited and chip flow is obstructed, disposable-insert tooling has not been widely used in trepanning.) The brazed cutter is designed so that the single edge has three steps to break the chip into three equal widths. Each step includes a parallel chip breaker. The cutter is commonly 19 mm ( in.) wide, but wider cutters have been successfully used for holes more than about 100 mm (4 in.) in diameter. Fig. 8 Typical design of a trepanning cutter for producing deep holes. Dimensions given in inches The radial position of the cutter when used in a stationary head is important.Viewed from the cutting end of the head, the cutter should be approximately at the 2 o'clock position; thus the cutting fluid will wash the chips away from the cutter through the relief on the outside diameter of the head, and the core, when cut, will fall away from the cutter. Multiple-cutter heads are sometimes more appropriate than those with single cutters. This is especially true when hole starting is difficult or for minimizing shock on the bar or other components in the driving mechanism. Example 4: Use of a Three-Cutter Head for Trepanning Transversely Through a Steel Cylinder. A 64 mm (2 in.) diam hole was trepanned through the 100 mm (4 in.) diameter of a solid cylinder of 8615 steel. A specially designed three-cutter head (Fig. 9) of 4140 steel was used in order to minimize spindle shock. This head, of the outside-diameter-exhaust type, included three 150 mm (6 in.) long bronze conventional wear strips, spaced 120° apart and 30° behind each cutter. To provide maximum stability and accuracy, an additional set of three cylindrical carbide wear strips (7.9 mm, or in. in diameter and 32 mm, or 1 in., long) was incorporated. A guide bushing was used in conjunction with a modified drill press that provided 22 kW (30 hp) at the spindle. Cutting fluid (active mineral oil) was pumped through the bar at 345 kPa (50 psi) and 380 L/min (100 gal./min). Fig. 9 Three-cutter trepanning head used for cutting a 64 mm (2 in.) diam hole through a solid cylinder of 8615 steel. Dimensions given in inches Four-Cutter Heads. Production rate can be increased with only a slight increase in feed rate or chip thickness, by the use of a four-cutter head. The first pair of cutters produces a narrow groove; this is then widened to final dimensions by the second pair of cutters. Initial and maintenance costs, however, are greater for this type of tool than for a single-cutter head. Figure 10 illustrates the recommended coolant pressure and flow rates for multiple-cutter internal chip removal trepanning tools. Fig. 10 Recommended coolant pressures (a) and volumes (b) for multiple- cutter internal chip removal trepanning tools Speed and Feed in Deep-Hole Trepanning Table 1 lists speeds and feeds for trepanning deep holes in a variety of carbon, alloy, and stainless steels. These values are useful as a starting point for selecting efficient and economical rates. [...]... 10 17, 1020, 1023, 1025 8 5-1 25 22 5-2 75 Medium carbon: 1030, 1033, 1035, 10 37, 1038, 1039, 1040, 1042, 1043, 1044, 1045, 1046, 1049, 1050, 1053, 1055, 1525, 1526, 15 27 12 5-1 75 37 5-4 25 Wrought alloy steels Low carbon: 4012, 4023, 4024, 4118, 4320, 4419, 4422, 4615, 46 17, 4620, 4621, 471 8, 472 0, 4815, 48 17, 4820, 5015, 5115, 5120, 6118, 8115, 86 17, 8620, 8622, 8822, 9310, 94B15, 94B 17 12 5-1 75 32 5-3 75 Medium... ( 27 ) 11 6 (38 ) 17 7 (58 ) 24 7 (81 ) 36 9 (12 1) 52 4 ( 17 2) 26 7. 3 (24 ) 10 4 (34 ) 15 8 (52 ) 21 9 (72 ) 32 9 (10 8) 46 9 (15 4) 70 1 (23 0) 3.4 (11 ) 4.0 (13 ) 4.6 (15 ) 4.9 (16 ) 5.2 ( 17 ) 5.5 (18 ) 5.8 (19 ) 6.1 (20 ) 6.4 (21 ) 6 .7 (22 ) 7. 0 (23 ) 7. 6 (25 ) 8.2 ( 27 ) 8.8 (29 ) 9.8 (32 ) 12 17 54 77 115 1 57 10 4.0 (1 3) 5.2 ( 17 ) 6.1 (20 ) 5.2 (1 7) ... P30 S9, S11(b) P30 S4, S5 P30 M2, M3 C-6 T15, M42(b) C-6 M2, M3 C-6 T15, M42(b) C-6 M2, M3 C-6 S4, S5 P30 S4, M2, M3 C-6 M2, 305, 308, 321, 3 47, 348, 384, 385 22 5-2 75 13 5-1 75 Annealed 69 27 225 90 0.10 0. 075 0.004 0.003 27 5-3 25 Quenched and tempered 76 15 250 50 0.15 0. 075 0.006 0.003 60 Martensitic: 403, 410, 420, 422, 501, 502 Cold drawn 84 18 275 60 0.15 0. 075 0.006 0.003 200 0.10 0.004 S5 K20 S4,... (1 7) 7. 0 (23 ) 8.5 (28 ) 150 (6) 7. 3 (24 ) 10 4 (34 ) 2 13 15 5.5 7. 9 10 7 4 1 2 (1 (2 (9) 8) 6) (34 (43 (50 ) ) ) 4 7. 6 11 14 18 21 0 (2 3 9 6 9 (1 (49 (61 (72 5) (3 3) 7) ) ) ) 5 11 17 22 27 32 3 1 3 7 9 8 (1 (3 (5 (73 (91 (10 7) 6) ) ) 8) 9) 7 15 23 30 38 44 9 5 2 5 7 8 (2 (5 (7 (10 (12 (14 6) 1) 6) 0) 7) 7) 600 mm (24 in.) standard shaper 500 mm (20 in.) heavy-duty shaper 0.9 1.5 2.1 2 .7 3.0... 2. 3-3 .8 (0.0900.150) 60 (200) 18 (60) 9 (30) 11 (35) 15 (50) 18 (60) 35 (120) 90 (300) 75 (250) max max max max Feed, mm (in.) per stroke 1. 5-2 .3 (0.0600.090) 1. 5-2 .3 (0.0600.090) 1. 5-2 .3 (0.0600.090) 1. 5-2 .3 (0.0600.090) 2. 3-3 .2 (0.0900.125) 2. 3-3 .2 (0.0900.125) 3. 2-4 .0 (0.1250.156) 12 (40) 1. 9-2 .3 (0. 075 0.090) 2. 3-2 .5 (0.0900.100) 1. 5-1 .9 (0.0600. 075 ) 1. 5-1 .9 (0.0600. 075 ) 1. 5-2 .3 (0.0600.090) 2. 3-3 .2... ( 27 ) 8.8 (29 ) 9.4 (31 ) 7. 3 (24 ) 8.2 ( 27 ) 9.1 (30 ) 11 (36 ) 14 9 (49 ) 22 6 (74 ) 32 3 (10 6) 47 5 (15 6) 13 4 (44 ) 18 6 (61 ) 28 (92 ) 11 3 ( 37 ) 17 1 (56 ) 23 5 (77 ) 36 (11 8) 11 9 (39 ) 18 3 (60 ) 25 (82 ) 51 2 (16 8) 38 1 (12 5) 12 5 (41 ) 19 5 (64 ) 26 5 ( 87 ) 40 5 (13 3) 42 7 (14 0) 10 7 (35 ) 13 7 (45 ) 21 6 (71 ) 29 3 (96 ) 44 8 (14 7) 11 6 ( 37 ) 14 6 (48 ) 22 9 (75 ... 2 .7 3.0 (3) (5) (7) (9) (10 ) 19 2 (63 ) 29 (95 ) 16 8 (55 ) 23 5 (77 ) 35 (11 5) 50 (16 4) 14 1.5 (5) 2.1 (7) 2 .7 (9) 3.4 (11 ) 4.0 (13 ) 4.6 (15 ) 5.2 ( 17 ) 5.8 (19 ) 6.4 (21 ) 7. 0 (23 ) 7. 3 (24 ) 7. 9 (26 ) 8.5 (28 ) 9.1 (30 ) 9.8 (32 ) 21 2.1 (7) 3.0 (1 0) 4.0 (13 ) 4.9 (16 ) 5.8 (19 ) 6 .7 (22 ) 7. 6 (25 ) 8.5 (28 ) 9.4 (31 ) 29 3.0 (1 0) 4.3 (1 4) 5.8 (19 ) 7. 0 (23 ) 8.2 ( 27 ) 9.8 (32 ) 11... Cast iron 175 90 (300) Steel 270 75 (250) Steel 200 max Steel 130 max Bronze Hard max Bronze Soft max (a) Feed, mm (in.) per stroke 2. 3-3 .2 (0.0900.125) 2. 3-3 .2 (0.0900.125) 1. 5-2 .3 (0.0600.090) 2. 3-3 .2 (0.0900.125) 2. 3-3 .2 (0.0900.125) 2. 3-3 .2 (0.0900.125) 4. 0-4 .8 (0.1560.188) 15 (50) 2. 3-3 .2 (0.0900.125) 2. 5-3 .2 (0.1000.125) 1. 5-1 .9 (0.0600. 075 ) 1. 5-2 .3 (0.0600.090) 1. 5-2 .3 (0.060.090) 2. 3-3 .2 (0.0900.125)... 115 9 375 30 0.15 0.10 0.006 0.004 90 17 300 55 0.13 0.13 0.005 0.005 105 350 0.15 0.006 Condition 10 0-1 50 Hot rolled or annealed 15 0-2 00 Wrought free -machining carbon steels Low-carbon resulfurized: 1 116, 11 17, 1118, 1119, 1211, 1212 Hardness, HB Cold drawn 17 5-2 25 Hot rolled, normalized, annealed, or cold drawn Quenched and tempered 32 5-3 75 Low-carbon leaded: 12L13, 12L14, 12L15 10 0-1 50 20 0-2 50 Wrought... 1. 1-1 .5 (0.0450.060) 1. 1-1 .5 (0.0450.060) 1. 1-1 .5 (0.0450.060) 1. 5-2 .3 (0.0600.090) 2. 3-3 .2 (0.0900.125) 1. 5-1 .9 (0.0600. 075 ) 1. 9-2 .3 (0. 075 0.090) 1. 1-1 .5 (0.0450.060) 1. 5-1 .9 (0.0600. 075 ) 1. 5-2 .3 (0.0600.090) 2. 3-2 .5 (0.0900.100) 2. 3-3 .2 (0.0900.125) 12 (40) 6 (20) 8 (25) 9 (30) 12 (40) 30 (100) 60 (200) Finishing speed(a), m/min (sfm) 12 (40) 18 (60) 6 (20) 9 (30) 15 (50) 18 (60) 45 (140) 1. 1-1 .5 . outside-diameter-exhaust heads are as follows: Diameter Depth mm in. mm in. 5 0-6 4 2-2 61 0 -7 62 2 4-3 0 6 5-8 9 2 -3 76 2-1 065 3 0-4 2 9 0-1 15 3 -4 106 5-1 78 0 4 2 -7 0 . 15 27 37 5-4 25 Quenched and tempered 100 325 0.13 0.005 P30 C-6 Wrought alloy steels 27 90 0.18 0.0 07 S4, S5 M2, M3 12 5-1 75 Hot rolled, annealed, or cold drawn 145 475 0.18 0.0 07. K20 C-2 27 90 0. 075 0.003 S4, S5 M2, M3 13 5-1 75 Annealed 76 250 0.15 0.006 P30 C-6 15 50 0. 075 0.003 S9, S11 (b) T15, M42 (b) Martensitic: 403, 410, 420, 422, 501, 502 27 5-3 25