All images courtesy of Pamela J. Tallman
Three axes of movement and ram movement on a Bridgeport milling machine.
The knee casting (lower left), the saddle and knee joined by their dovetails (lower right) and the knee, saddle and milling table together (top).
Eagle Machine Inc., in Abbotsford, B.C., frequently takes on challenging jobs, such as modifying a diving bell for deep-sea submarine rescues or designing and machining a set of solid aluminum wheels for an 800-mph land speed car based on an F-104 jet aircraft. Owner Steve Green said, “People come to us with the craziest things because other people tell them, ‘the only place you can go is Eagle Machine.’ ”
One customer needed a durable crankshaft for a 1,000-hp drag racing motorcycle engine. As a result, Eagle redesigned the engine and now produces it as the “Nitro V45.” Based on a 45° V-Twin Harley-Davidson engine, the normally aspirated (nonsupercharged) motor displaces up to 200 cu. in., burns nitromethane fuel and can send a bike through the quarter mile in about 6 seconds, reaching a top speed of 235 mph.
The engine’s block and heads are aluminum, but the crankshaft needs to be made of tougher material. Nitromethane carries its own oxygen and boosts power—and thereby stress on engine components—by a factor of 10. “You are hitting the crank with a big sledge hammer when you pour in nitromethane,” Green said. “The crankshaft is the heart of the engine.”
Accordingly, Eagle Machine determined that the best crankshaft material is EN30B steel alloy from Corus Group in the U.K. Green said the alloy is similar to 4340 steel but has more than 4 percent nickel content, compared to 4340’s 2 percent or less. The alloy’s high nickel content lets the crankshaft endure considerable flexing without cracking, but the increased toughness makes the steel more difficult to machine.
The shop acquires the alloy, in 23- to 25-HRC annealed condition, from distributor Encore Metals as 20 '-long, 8⅞ "-dia. bars in minimum shipments of 20,000 lbs. “We make 25 crankshafts at a time and 20,000 lbs. will make four batches,” Green said.
The bar is sawed into 9 " lengths and chucked on a Daewoo Puma 300L CNC lathe, where half of the part is rough turned from a maximum OD of 8⅝ " down to a 2.776 " main bearing journal diameter. For rough turning, Eagle Machine uses a Sandvik Coromant grade-4015 CNMG 433 PR insert, applied at 300 sfm, a 0.150 " DOC and a 0.018-ipr feed rate. The part is then flipped for similar operations on the other end. Roughing leaves 0.030 " excess stock on the part for finish grinding after heat treatment.
After rough turning, the crankshaft is moved to a Haas CNC mill where the shop employs ballnose endmills to machine lightening pockets into half of the face of each end of the crankshaft.
Next, the shop rough mills the part’s crankpin on a Takumi Seiki V10 AH vertical machining center fitted with a 4th- axis rotary table. The finished diameter of the crankpin, on which the pistons’ connecting rods ride, is 2.375 ". To hold the part in the mill, “we have a fixture on the rotary table that we chuck onto one journal, and we stick a tailstock into the other journal to give it rigidity,” said CNC Supervisor Dave Krol. A 50mm-dia., square-corner Iscar shell mill, tooled with five Iscar grade-950 inserts, then cuts a space in the middle of the crankshaft, creating two flywheels and the crankpin. The milling cutter is mounted on a 4 "-long extension made of tungsten to provide rigidity and dampen vibration.
Krol said the milling inserts run dry and “really hot.” They’re applied at a 0.100 " DOC and a 100-ipm feed rate. To machine the crankpin, “we bring the leading edge of the cutter in line with the center axis of the part diameter, and as the rotary table turns we move the Z-axis up and down to compensate for the throw of the crankpin,” he said. Because the cutter isn’t directly on center, the crankpin has a convex contour. The rough-milled crankpin has ¼ " of excess material, which is removed on a manual lathe. On the same machine, the inner sides of the flywheels are faced smooth.
Back on the Takumi VMC, Eagle Machine rough drills nine through-holes in each flywheel (opposite the lightened areas) to accommodate tungsten counterweights that balance the mass of the pistons and rods on the offset crankpin. The 1 "-dia., 11⁄8 "-long plugs weigh 5⁄8 lb. each. Tungsten is 2.5 times heavier than steel, and each crankshaft contains about $400 worth of the heavy metal.
The crankshaft is sent to Cascade Metallurgical, Kent, Wash., where it is hardened in a vacuum furnace to 42 to 43 HRC. It is quenched in high-pressure nitrogen gas, which produces less distortion than oil quenching, Green said.
The crankshafts are returned to Eagle where they are semifinish turned. “The sizes are tight and a cutting edge will only maybe last a couple of parts,” Krol said. “It seems that every time you get your size set on the CNC lathe, your insert goes. Speeds run about half of what we were turning it before heat treat. Our feeds are fine, around 0.005 to 0.006 ipr. We have to maintain a good surface finish. At this point, we are shooting for a 32µin. Ra finish for the journals, but the flywheels don’t really matter.”
Next, holes for the tungsten plugs are finish-bored on the Takumi mill. Krol said the plugs themselves are ground to a tolerance of -0.000 "/+0.0005 ", and “we maintain 0.001 " of interference tolerance for the holes.” Final machining involves manually drilling and boring pinion holes for the cam gear.
After quality assurance examination, the crankshaft goes to Lopez Crank Shaft, Santa Fe Springs, Calif., which grinds the two main bearing journals and the crank pin. The shop holds ±0.0001 " on diameters, ±0.0005 " on stroke length and produces a 5 to 8 µin. Ra finish. Green said Lopez has “never screwed up a crankshaft,” such as by burning the radiuses, a common error that can lead to microcracking.
The crankshaft is shipped to Accurate Ion Technologies, South Gate, Calif., for an ion-nitriding surface hardening process set at 700° F to avoid softening the part’s core hardness.
When the crankshaft returns to Eagle Machine, the tungsten plugs are pressed in and it receives a final surface treatment called Harperizing. Green said his shop has the only Harperizing machine in western Canada; it consists of a 5 '-dia., 2 "-thick steel wheel with two rubber lined tubs at its periphery. Parts are finished with a silicon-carbide media and a water-based lubricant at a force of as much as 25 Gs.
Green said his shop’s $4,000 crankshafts last at least twice as long as the competition, completing perhaps 250 to 300 quarter-mile runs before replacement. “It took us a year to develop the process for this part because nobody in the racing crank business is going to tell you anything,” he said. CTE
For more information about Eagle Machine Inc., call (866) 852-1277 or visit www.eaglemachine.ca.
Courtesy of Eagle Machine
Eagle Machine manufactures this 85⁄8 "-dia., 9 "-long crankshaft for a 1,000-hp motorcycle engine from EN30B steel alloy. At the left end is a 9310 alloy cam drive gear hobbed by the shop, and on the right end is a 4 "-wide black-anodized 7075 aluminum toothed pulley that drives a Kevlar-reinforced toothed belt to transfer power to the motorcycle gearbox.
Related Glossary Terms
- boring
boring
Enlarging a hole that already has been drilled or cored. Generally, it is an operation of truing the previously drilled hole with a single-point, lathe-type tool. Boring is essentially internal turning, in that usually a single-point cutting tool forms the internal shape. Some tools are available with two cutting edges to balance cutting forces.
- burning
burning
Rotary tool that removes hard or soft materials similar to a rotary file. A bur’s teeth, or flutes, have a negative rake.
- chuck
chuck
Workholding device that affixes to a mill, lathe or drill-press spindle. It holds a tool or workpiece by one end, allowing it to be rotated. May also be fitted to the machine table to hold a workpiece. Two or more adjustable jaws actually hold the tool or part. May be actuated manually, pneumatically, hydraulically or electrically. See collet.
- computer numerical control ( CNC)
computer numerical control ( CNC)
Microprocessor-based controller dedicated to a machine tool that permits the creation or modification of parts. Programmed numerical control activates the machine’s servos and spindle drives and controls the various machining operations. See DNC, direct numerical control; NC, numerical control.
- computer-aided manufacturing ( CAM)
computer-aided manufacturing ( CAM)
Use of computers to control machining and manufacturing processes.
- feed
feed
Rate of change of position of the tool as a whole, relative to the workpiece while cutting.
- fixture
fixture
Device, often made in-house, that holds a specific workpiece. See jig; modular fixturing.
- gang cutting ( milling)
gang cutting ( milling)
Machining with several cutters mounted on a single arbor, generally for simultaneous cutting.
- grinding
grinding
Machining operation in which material is removed from the workpiece by a powered abrasive wheel, stone, belt, paste, sheet, compound, slurry, etc. Takes various forms: surface grinding (creates flat and/or squared surfaces); cylindrical grinding (for external cylindrical and tapered shapes, fillets, undercuts, etc.); centerless grinding; chamfering; thread and form grinding; tool and cutter grinding; offhand grinding; lapping and polishing (grinding with extremely fine grits to create ultrasmooth surfaces); honing; and disc grinding.
- hardening
hardening
Process of increasing the surface hardness of a part. It is accomplished by heating a piece of steel to a temperature within or above its critical range and then cooling (or quenching) it rapidly. In any heat-treatment operation, the rate of heating is important. Heat flows from the exterior to the interior of steel at a definite rate. If the steel is heated too quickly, the outside becomes hotter than the inside and the desired uniform structure cannot be obtained. If a piece is irregular in shape, a slow heating rate is essential to prevent warping and cracking. The heavier the section, the longer the heating time must be to achieve uniform results. Even after the correct temperature has been reached, the piece should be held at the temperature for a sufficient period of time to permit its thickest section to attain a uniform temperature. See workhardening.
- hardness
hardness
Hardness is a measure of the resistance of a material to surface indentation or abrasion. There is no absolute scale for hardness. In order to express hardness quantitatively, each type of test has its own scale, which defines hardness. Indentation hardness obtained through static methods is measured by Brinell, Rockwell, Vickers and Knoop tests. Hardness without indentation is measured by a dynamic method, known as the Scleroscope test.
- land
land
Part of the tool body that remains after the flutes are cut.
- lathe
lathe
Turning machine capable of sawing, milling, grinding, gear-cutting, drilling, reaming, boring, threading, facing, chamfering, grooving, knurling, spinning, parting, necking, taper-cutting, and cam- and eccentric-cutting, as well as step- and straight-turning. Comes in a variety of forms, ranging from manual to semiautomatic to fully automatic, with major types being engine lathes, turning and contouring lathes, turret lathes and numerical-control lathes. The engine lathe consists of a headstock and spindle, tailstock, bed, carriage (complete with apron) and cross slides. Features include gear- (speed) and feed-selector levers, toolpost, compound rest, lead screw and reversing lead screw, threading dial and rapid-traverse lever. Special lathe types include through-the-spindle, camshaft and crankshaft, brake drum and rotor, spinning and gun-barrel machines. Toolroom and bench lathes are used for precision work; the former for tool-and-die work and similar tasks, the latter for small workpieces (instruments, watches), normally without a power feed. Models are typically designated according to their “swing,” or the largest-diameter workpiece that can be rotated; bed length, or the distance between centers; and horsepower generated. See turning machine.
- machining center
machining center
CNC machine tool capable of drilling, reaming, tapping, milling and boring. Normally comes with an automatic toolchanger. See automatic toolchanger.
- milling
milling
Machining operation in which metal or other material is removed by applying power to a rotating cutter. In vertical milling, the cutting tool is mounted vertically on the spindle. In horizontal milling, the cutting tool is mounted horizontally, either directly on the spindle or on an arbor. Horizontal milling is further broken down into conventional milling, where the cutter rotates opposite the direction of feed, or “up” into the workpiece; and climb milling, where the cutter rotates in the direction of feed, or “down” into the workpiece. Milling operations include plane or surface milling, endmilling, facemilling, angle milling, form milling and profiling.
- milling cutter
milling cutter
Loosely, any milling tool. Horizontal cutters take the form of plain milling cutters, plain spiral-tooth cutters, helical cutters, side-milling cutters, staggered-tooth side-milling cutters, facemilling cutters, angular cutters, double-angle cutters, convex and concave form-milling cutters, straddle-sprocket cutters, spur-gear cutters, corner-rounding cutters and slitting saws. Vertical cutters use shank-mounted cutting tools, including endmills, T-slot cutters, Woodruff keyseat cutters and dovetail cutters; these may also be used on horizontal mills. See milling.
- milling machine ( mill)
milling machine ( mill)
Runs endmills and arbor-mounted milling cutters. Features include a head with a spindle that drives the cutters; a column, knee and table that provide motion in the three Cartesian axes; and a base that supports the components and houses the cutting-fluid pump and reservoir. The work is mounted on the table and fed into the rotating cutter or endmill to accomplish the milling steps; vertical milling machines also feed endmills into the work by means of a spindle-mounted quill. Models range from small manual machines to big bed-type and duplex mills. All take one of three basic forms: vertical, horizontal or convertible horizontal/vertical. Vertical machines may be knee-type (the table is mounted on a knee that can be elevated) or bed-type (the table is securely supported and only moves horizontally). In general, horizontal machines are bigger and more powerful, while vertical machines are lighter but more versatile and easier to set up and operate.
- milling machine ( mill)2
milling machine ( mill)
Runs endmills and arbor-mounted milling cutters. Features include a head with a spindle that drives the cutters; a column, knee and table that provide motion in the three Cartesian axes; and a base that supports the components and houses the cutting-fluid pump and reservoir. The work is mounted on the table and fed into the rotating cutter or endmill to accomplish the milling steps; vertical milling machines also feed endmills into the work by means of a spindle-mounted quill. Models range from small manual machines to big bed-type and duplex mills. All take one of three basic forms: vertical, horizontal or convertible horizontal/vertical. Vertical machines may be knee-type (the table is mounted on a knee that can be elevated) or bed-type (the table is securely supported and only moves horizontally). In general, horizontal machines are bigger and more powerful, while vertical machines are lighter but more versatile and easier to set up and operate.
- outer diameter ( OD)
outer diameter ( OD)
Dimension that defines the exterior diameter of a cylindrical or round part. See ID, inner diameter.
- quality assurance ( quality control)
quality assurance ( quality control)
Terms denoting a formal program for monitoring product quality. The denotations are the same, but QC typically connotes a more traditional postmachining inspection system, while QA implies a more comprehensive approach, with emphasis on “total quality,” broad quality principles, statistical process control and other statistical methods.
- quenching
quenching
Rapid cooling of the workpiece with an air, gas, liquid or solid medium. When applicable, more specific terms should be used to identify the quenching medium, the process and the cooling rate.
- tolerance
tolerance
Minimum and maximum amount a workpiece dimension is allowed to vary from a set standard and still be acceptable.
- turning
turning
Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.
Author
News items authored by Cutting Tool Engineering have been written or edited by the editors of Cutting Tool Engineering magazine. The reports represent material submitted to CTE by outside authors, and edited by CTE editors for style and accuracy.
