The reamer line’s monoblock style covers hole diameters from 5.8 mm to 32.1 mm  (0.228" to 1.264") while the replaceable-head series is slightly larger at 11.8 mm to 60.6 mm (0.465" to 2.386"). Both kinds are available in fixed or expandable models. There’s also a ring-style reamer that ranges from 17.6 mm to 200.6 mm (0.693" to 7.898").

Some machine builders, Hardinge included, offer turning and grinding machines, making them trusted advisers on which process is most suitable for a given part. Another is EMAG LLC USA, Farmington Hills, Mich., which also offers machines that grind and hard-turn. The company’s director of sales, Kirk Stewart, agreed that hard turning offers many opportunities for improvement in productivity and part quality, and proper machine design is critical to success.

“In most applications, we can easily hold hole size within 5 µm (0.0002") even while feeding 50% faster than a traditional carbide reamer,” Vetrecin said. “This makes our system a favorite in the aerospace, automotive and indeed any industry where hole quality is just as important as throughput.”

Crystal manufactured from boron nitride under high pressure and temperature. Used to cut hard-to-machine ferrous and nickel-base materials up to 70 HRC. Second hardest material after diamond. See superabrasive tools.

“Alternatively, when the machine architecture allows, a combined configuration of turning and grinding can become very attractive for mid-volume requirements, an architecture that EMAG machines inherently provide.”

“It’s a very versatile product line,” Morrett said. “We have different grades of cermet, carbide, PCD and CBN available, as well as various coatings and geometries, so there’s little we can’t handle materialwise. With that in mind, I would say that most of our customers are using them for production work, such as hydraulic manifolds and firearm components.”

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Condition of vibration involving the machine, workpiece and cutting tool. Once this condition arises, it is often self-sustaining until the problem is corrected. Chatter can be identified when lines or grooves appear at regular intervals in the workpiece. These lines or grooves are caused by the teeth of the cutter as they vibrate in and out of the workpiece and their spacing depends on the frequency of vibration.

Turning with ceramic inserts is usually done dry. Here the toolholder is mounted face up, driving cutting forces down into the machine’s load-bearing surfaces. Image courtesy Greenleaf.

Engagement of a tool’s cutting edge with a workpiece generates a cutting force. Such a cutting force combines tangential, feed and radial forces, which can be measured by a dynamometer. Of the three cutting force components, tangential force is the greatest. Tangential force generates torque and accounts for more than 95 percent of the machining power. See dynamometer.

Since the early 2000s, Allied Machine & Engineering has partnered with S.C.A.M.I., a manufacturer of modular reamers.  Image courtesy of Allied Machine & Engineering

“Hard turning offers lower machine investment, reduced setup and tool inventory, fewer operations, faster cycle times and greater process flexibility,” he said. “Unfortunately, many shops can use it only for semifinishing of parts prior to grinding, primarily because the majority of CNC lathes are unable to achieve the extreme tolerances and form accuracy produced by cylindrical grinding machines.”

Ceramics should be run dry in hardened materials, Kohler said. He recommends Greenleaf’s WG-600 silicon-nitride grade—a CVD-coated version of the company’s whisker-reinforced WG-300—as a good starting point for most hardened steels, as well as its new XSYTIN-1, a phase-toughened ceramic grade designed specifically for high-performance roughing and interrupted cuts.

Horn added to its Supermini line for boring workpieces as hard as 66 HRC without the use of PCBN. Image courtesy Horn USA Inc., Nico Sauermann.

Lastly, don’t forget to properly align a reamer. Some toolmakers offer adjustable sleeves or adapters for machines with out-of-whack turrets and spindles. Otherwise, a high-quality hydraulic holder is the best way to grip any reamer while avoiding floating holders whenever possible.

“The vast majority of machined holes are 9⁄16" (14.29 mm) in diameter or smaller,” he said, “and for most of these, solid reamers are the best choice. For larger diameters, however, the PXM lineup provides the advantages of a solid cutting tool with the flexibility and cost benefit of an indexable platform.”

Indexable ceramics are another option. Jack Kohler, applications engineer for Greenleaf Corp., Saegertown, Pa., said the cost of ceramic cutting tools falls somewhere between PCBN and carbide, and offers equivalent or better performance in some applications. “Ceramic does quite well in the 50-HRC to 65-HRC range,” he said. “Cutting speeds would be comparable to PCBN. Figure around 700 sfm on a 55-HRC A-2 tool steel, for example, with only slightly lower tool life.”

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.

Hard turning is used to finish a variety of parts, such as bearing journals and races, brake drums and rotors, cylinder bore liners, gears, pinions and splines—or to semifinish those same components prior to grinding. Properly applied, it achieves an accuracy best measured in microns and, in many cases, is faster and more cost-effective than cylindrical grinding.

Substances having metallic properties and being composed of two or more chemical elements of which at least one is a metal.

Hole quality is also a critical factor when selecting a reamer, he said. Iscar’s Bayo T-Ream interchangeable-head reamer, which covers diameters from 11.5 mm to 32 mm (0.453" to 1.26"), guarantees diametral head accuracy of ±2.03 µm (0.00008") and 3 µm (0.0001") runout and indexing repeatability.

“Whether modular, HSS or solid carbide, hole quality and tool life both depend on minimizing runout when reaming,” Vetrecin said.

Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.

The Bayo T-Ream reamer  from Iscar is equipped with a bayonet screw and special wrench for rapid changeovers. Image courtesy of Iscar Metals

“Because only the head of the tool is made of carbide, it’s a much more cost-effective solution for large-diameter reaming applications,” he said.

What if you need to go even larger? Talk to Ben Morrett, senior product manager for the Alvan reamer line at Allied Machine & Engineering Corp., Dover, Ohio. Since the early 2000s, the company has partnered with S.C.A.M.I. snc, a family-owned reamer manufacturer in Italy that produces modular reamers up to nearly 203.2 mm (8") in diameter.

Fluid that reduces temperature buildup at the tool/workpiece interface during machining. Normally takes the form of a liquid such as soluble or chemical mixtures (semisynthetic, synthetic) but can be pressurized air or other gas. Because of water’s ability to absorb great quantities of heat, it is widely used as a coolant and vehicle for various cutting compounds, with the water-to-compound ratio varying with the machining task. See cutting fluid; semisynthetic cutting fluid; soluble-oil cutting fluid; synthetic cutting fluid.

A number of cutting tool manufacturers have resurrected Gyllsdorff’s idea and made it better. Peter Gennuso, sales engineering manager for OSG USA Inc., Irving, Texas, said the company’s PXM endmill platform can be equipped with a variety of heads, including special form tools, chamfer and radius cutters or exchangeable-head reamers.

“Reamers are designed to remove a relatively small amount of material,” he said. “But with the larger diameters like those discussed here, your drilling options are more limited. So it might be necessary to drill as close as you can, semifinish with a boring tool and then ream to size. Without that three-step process, it can be tough to guarantee the proper amount of finishing stock and avoid problems with chip evacuation.”

Grooves and spaces in the body of a tool that permit chip removal from, and cutting-fluid application to, the point of cut.

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.

He said his statement about production work is not meant to scare off job shops and other high-mix, low-volume manufacturers that benefit from the product’s broad application range and ability to expand holes up to 1% of a reamer’s diameter. The sticking point is cost: Whereas a five-person shop might balk at spending an additional 30% or more for a modular reamer, high-volume manufacturers easily can justify it based on cost per hole.

Some might wonder about the difference between hard turning the inside of a part (boring) and its outside. Most agree that boring is generally more difficult than OD turning, regardless of material hardness. That’s because boring bars are less rigid than other turning tools, creating problems with chatter and tool deflection. Because quarters are often tight in a bored hole, chip evacuation can be a challenge, leading to coolant starvation and workpiece galling. In addition, achieving sufficient surface speeds becomes increasingly difficult for small part features, such as bores, and PCBN and ceramic inserts require high cutting speeds.

Cutting tool material consisting of polycrystalline cubic boron nitride with a metallic or ceramic binder. PCBN is available either as a tip brazed to a carbide insert carrier or as a solid insert. Primarily used for cutting hardened ferrous alloys.

“An often-overlooked component of ID work is accounting for the axial, radial and tangential cutting forces produced when turning,” said Mike Csizmar, regional sales manager at Horn USA Inc., Franklin, Tenn. “This is also true on external operations, but due to the increased L:D ratios associated with boring, these forces become more pronounced, affecting dimensional qualities. If you have a choice, axial (Z-axis) cutting force is preferred. A rule of thumb is that DOC should be equal to or greater than the tool nose radius, thus generating greater axial force. This provides the ability to control chatter, diameter and taper in a more efficient manner, and allows you to get the most out of your cutting tool.”

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Monitor tool life, and replace tools sooner rather than later, especially if there’s the possibility of regrinding a tool, he said. Because penetration rates are often much higher with modular reamers — primarily due to the advanced edge geometries and coatings from most cutting tool providers — always follow a manufacturer’s recommendations for feeds and speeds.

Kip Hanson is a contributing editor for Cutting Tool Engineering magazine. Contact him by phone at (520) 548-7328 or via e-mail at kip@kahmco.net.

These reamers are also quite accurate. In OSG USA’s case, the PXM offers 0.015 mm (0.0006") or less of radial runout and axial repeatability within ±0.03 mm (0.0012"). This is accomplished via a buttress-style, screw-on carbide head whose face and taper mate with a cylindrical steel shank, similar to an HSK spindle or a comparable dual-contact mount.

Grinding operation in which the workpiece is rotated around a fixed axis while the grinding wheel is fed into the outside surface in controlled relation to the axis of rotation. The workpiece is usually cylindrical, but it may be tapered or curvilinear in profile. See centerless grinding; grinding.

Brazed carbide reamers are one option, but a better alternative dates back a century. On Dec. 27, 1920, inventor Torsten A. Gyllsdorff of Detroit-based Standard Reamer & Tool Co. applied for a patent for a two-piece reamer, one “wherein the cutting end can be replaced at low cost when worn.” His “new and improved reamer” unfortunately used an HSS head, which minimized improvements to productivity, but hats off to his forward thinking regardless.

Tangential velocity on the surface of the tool or workpiece at the cutting interface. The formula for cutting speed (sfm) is tool diameter 5 0.26 5 spindle speed (rpm). The formula for feed per tooth (fpt) is table feed (ipm)/number of flutes/spindle speed (rpm). The formula for spindle speed (rpm) is cutting speed (sfm) 5 3.82/tool diameter. The formula for table feed (ipm) is feed per tooth (ftp) 5 number of tool flutes 5 spindle speed (rpm).

Gennuso said a general rule is to leave 1% of a hole’s finished diameter for reaming. For a 12.7 mm hole, that would mean drilling to 12.57 mm (0.495"). Check any drill chart, however, and you’ll find that the nearest drill size is 12.3 mm (0.484"), roughly three times his recommendation. So what do you do?

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.

Kohler said he’s seeing increased use of ceramic in high-temperature alloys, such as Inconel 718 and Hastelloy, although he warns shops to steer clear of titanium, as this presents a fire risk because titanium chips can burst into flames at the high cutting speeds common with ceramics. Regardless of the metal being cut, ceramic inserts usually come with a slight hone, land or combination of the two at the cutting edge to prevent chipping and increase strength.

For many shops, the move to solid-carbide reamers is a no-brainer. Yes, the price may be several times that of their HSS equivalent, but the higher productivity and hole quality are enough to win over even the most frugal shop owners and purchasing managers — that is, until reaching hole sizes of 12.7 mm (0.5") and larger, at which point a solid-carbide reamer becomes increasingly hard to justify. What then?

Cutting tool materials based on aluminum oxide and silicon nitride. Ceramic tools can withstand higher cutting speeds than cemented carbide tools when machining hardened steels, cast irons and high-temperature alloys.

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.

Opinions vary on the definition of hard turning. Some industry experts say it’s the single-edge cutting of hardened steels from 58 to 68 HRC, while others suggest hard turning begins at 45 HRC and includes hardened irons and superalloys. All, however, agree it presents difficulties but is quite manageable provided the right cutting tools, machine and process parameters are used.

Despite these capabilities, some parts are not suitable for hard turning. Bearing seals, for example, often call for ground surfaces, which eliminate the possibility of fluid escaping through what is essentially a microscopic thread-wide channel produced by single-point turning. And the “white zone” created when material softens and subsequently rehardens during turning (and grinding to a lesser extent) may cause premature component failure. Sheehy said both of these situations can be minimized with the right tooling and a few process adjustments.

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Kip Hanson is a contributing editor for Cutting Tool Engineering magazine. Contact him by phone at (520) 548-7328 or via e-mail at kip@kahmco.net.

Do you still use that old standby, the HSS chucking reamer, for hole-finishing operations? There are excellent reasons to do so. HSS chucking reamers are inexpensive, dependable, readily available and forgiving of misalignment and misuse. For example, one catalog house lists more than 5,000 HSS reamers on its website, most of them in stock. But if you decided a long time ago to ditch HSS hand-ground tool bits for carbide ones, it might be time to question why you haven’t taken the same route for reamers.

Because only the head of the tool is made of carbide, modular reamers are cost-effective for many reaming applications. Image courtesy of OSG USA

CNC grinders are routinely called upon to produce part roundness of 1μm (0.00004"), maintain diametral tolerances of ±2.5μm (0.0001") and impart surface finishes as fine as 8 rms or finer. Sheehy said the only way a CNC lathe can compete in this arena is if it is designed from the ground up for hard turning.

Angle between the side-cutting edge and the projected side of the tool shank or holder, which leads the cutting tool into the workpiece.

Groove or other tool geometry that breaks chips into small fragments as they come off the workpiece. Designed to prevent chips from becoming so long that they are difficult to control, catch in turning parts and cause safety problems.

When drilling, a force that is directed axially—along the direction of machining. The magnitude of an axial force rises with the drill’s diameter and the chisel edge’s width. Axial force is also known as thrust. When turning and boring, the term “feed force” is commonly used instead of “axial force.” See cutting force.

Graham said the company’s TH carbide can successfully turn materials up to 65 HRC and, unlike PCBN, is available in a range of geometries and chipbreaker configurations. And carbide is less prone to breakage in some applications—a casehardened shaft, for example, where it’s possible that softer material might be encountered, which would quickly dissolve the cutting edge and spell near-certain doom for the PCBN insert.

Vetrecin said the rules are no different when using modular or conventional reamers. For the best chip evacuation on through-holes, always use a tool with left-hand flutes, which push chips forward. Blind-holes should be reamed with a straight-flute tool or right-hand tool, if available. Since most modular reamers offer through-the-tool coolant, by all means use it, preferably with high-pressure coolant.

The solution, experts agree, is to apply the shortest tool possible relative to tool diameter, preferably no greater than a 4:1 length-to-diameter (L:D) ratio. Boring bars should be on center or, in some cases, a few tenths (0.0003") above center to allow for deflection. And use a boring insert with a 0° lead angle whenever possible, so cutting forces are directed opposite the direction of cut.

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.

“I worked with a shop recently that was getting around 1,000 parts out of a brazed carbide reamer,” Morrett said. “By switching to our Alvan solution, they increased that to 14,000 parts. So, yes, our tool costs roughly one-third more than a conventional reamer, but the delta is insignificant when you consider the productivity improvements.”

Distance between the bottom of the cut and the uncut surface of the workpiece, measured in a direction at right angles to the machined surface of the workpiece.

Tom Sheehy, applications engineering manager for Hardinge Inc., Elmira N.Y., said hard turning can be performed on virtually any lathe and provides many benefits.

“A cutting speed of 600 sfm is a good starting point for PCBN,” he said. “We recommend a double-sided round insert where possible, carefully rotating it as the tool wears. Depending on depth of cut, this might provide 10 to 20 uses per side. Some shops are scared off by the relatively high price of these inserts, however. In these cases, we’d likely suggest a PCBN-tipped insert —or even one of our new superhard carbide grades.”

Condition whereby excessive friction between high spots results in localized welding with subsequent spalling and further roughening of the rubbing surface(s) of one or both of two mating parts.

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.

“If you’re only doing a handful of parts, it’s probably most cost-effective to use a standard HSS or brazed carbide reamer,” said David Vetrecin, holemaking product manager for Iscar Tools Inc., Oakville, Ontario. “Modular reamers are more suitable for production work where cycle time is critical.”

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.

Let’s start with cutting tools. Don Graham, manager of education and technical services for Seco Tools LLC, Troy, Mich., said that if the setup is fairly rigid and the correct cutting parameters can be achieved, indexable PCBN inserts are generally the best bet for hard turning.

Main body of a tool; the portion of a drill or similar end-held tool that fits into a collet, chuck or similar mounting device.

Throughput also depends on setup time, and modular reamers don’t disappoint. The Bayo T-Ream, for example, is equipped with a bayonet screw and special wrench for rapid changeovers. Perhaps more important than speed is simplicity, however. Considering the shortage of qualified workers, modular reamers offer a set-it-once approach, after which anyone can replace heads with a screwdriver.

Secures a cutting tool during a machining operation. Basic types include block, cartridge, chuck, collet, fixed, modular, quick-change and rotating.

Rotating cutting tool used to enlarge a drilled hole to size. Normally removes only a small amount of stock. The workpiece supports the multiple-edge cutting tool. Also for contouring an existing hole.

What defines large? Depending on the style of head, the PXM system covers diameters from 10 mm to 32 mm (0.39" to 1.26"), a range that Gennuso said complements OSG USA’s solid-carbide reamer line.

Cutting tool material consisting of natural or synthetic diamond crystals bonded together under high pressure at elevated temperatures. PCD is available as a tip brazed to a carbide insert carrier. Used for machining nonferrous alloys and nonmetallic materials at high cutting speeds.

Initially, carbide is also less expensive, although Graham pointed out that cost per edge favors PCBN. “PCBN might cost 10 to 25 times more than carbide, but you’re also going to get 50 to 100 times the tool life. Certainly, for high production, PCBN is the way to go.”

Available in two major types: tungsten high-speed steels (designated by letter T having tungsten as the principal alloying element) and molybdenum high-speed steels (designated by letter M having molybdenum as the principal alloying element). The type T high-speed steels containing cobalt have higher wear resistance and greater red (hot) hardness, withstanding cutting temperature up to 1,100º F (590º C). The type T steels are used to fabricate metalcutting tools (milling cutters, drills, reamers and taps), woodworking tools, various types of punches and dies, ball and roller bearings. The type M steels are used for cutting tools and various types of dies.

“Hardinge Super-Precision lathes offer 0.1μm programmable resolution,” he said. “Axial errors are mapped and compensated for electronically. All mating surfaces within the machine are hand-scraped, the linear guide ways and ballscrews are oversized, and the base of the machine is filled with composite polymer for vibration damping. Not only does this produce the accuracy and rigidity needed to replace many grinding operations, it also increases tool life during hard turning by up to 30 percent.”

Milling cutter held by its shank that cuts on its periphery and, if so configured, on its free end. Takes a variety of shapes (single- and double-end, roughing, ballnose and cup-end) and sizes (stub, medium, long and extra-long). Also comes with differing numbers of flutes.

“A significant benefit of changing from grinding to hard turning is the reduction in capital investment,” Stewart said. “Grinding, however, does have its place and is, in some instances, a faster process when multiple features are ground simultaneously—a situation that is ideal for high-volume applications. Thus, in a high-volume environment, when there are only one or two features that require finishing, hard turning might be the better process for overall capital investment.