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“Successful chip management of cast iron, alloy, and carbon steel makes applications in automotive, general purpose, heavy equipment, machine tools, off-road, and the heat exchanger industries good candidates for the LOGIQ3CHAM,” Ewing said. “The heat exchanger industry, for example, uses standard ISO P materials and drills holes by the thousands. When you are drilling thousands of holes in one part, like a heat exchanger, you can see the benefit of increasing feed rate by up to 50 percent,” Ewing said, adding that new geometries are being developed for materials such as stainless and high-temperature alloys.

As a result, he said, Big Daishowa is focused on high-quality toolholders and boring tools. The company’s Phoenix TC2 solid-carbide drills, which also are designed for high-production applications—in sizes up to 30xD and 10 mm diameters—and high-temperature alloys, feature coatings, coolant-through holes, and efficient chip evacuation to insulate against cutting heat, according to Kerlin.

“A typical job shop application might involve a clearance hole for a bolt head where conventional tolerance doesn’t mean that much for clearance and an indexable might be the most economical solution. If you’re just punching a hole, an indexable makes a lot of sense. The reality is that if you are going to do secondary operations afterward, it doesn’t make sense to spend the money to buy a solid-carbide drill. At that point you are probably in between using an exchangeable tip or using an indexable,” Andersson explained. “The benefit of the indexable is that it is the most versatile, especially when you’re using the WCMX trigon-style drill. You can offset it so that can drill oversize, you can chamfer the hole after drilling.”

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.

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.

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.

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.”

“Our GEN3SYS XT and GEN3SYS XT Pro high-penetration carbide drills are indexable so they’ll go on a high-speed steel body, which still allows for a cost reduction versus the prototypical solid-carbide drill,” Weniger added. “The Superion line of special solid-carbide drills and PCD tools are high-performance, high-penetration-style drills.”

However, he conceded, picking the more expensive option isn’t always the best choice. “If you’re a job shop, there’s nothing wrong with using less expensive tools for one-offs,” Kerlin pointed out. “Everything has its place. But once you start moving into high-production territory, in the long run using cheaper tooling will almost always cost you more money in the form of broken tools, poor surface finish, increased scrap, and machine downtime.”

Here’s how some leading suppliers have shaped their drilling solutions. The goal is to maximize performance, while meeting material, production volume, and hole quality requirements.

For holemaking in aluminum, Emuge developed the new PunchDrill, a high-productivity tool that reduces machining forces and optimizes chip breaking, producing cycle time savings of 50 percent or more when machining cast-aluminum alloys with at least seven percent silicon content and magnesium alloys. The PunchDrill doubles the feed rate compared with standard drills, without increasing axial force or spindle speed—and results in shorter machining times, fewer tool changes, and high metal-removal rates—in addition to higher productivity and reduced power consumption, according to the company.

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.

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.

Job shop or high production? According to two product managers at Allied Machine & Engineering Corp., Dover, Ohio, the challenge to satisfy the requirements of both is the same: Provide drilling solutions that enable customers to meet their production requirements in a timely and cost-efficient manner.

“Toolholders are also extremely important for high-production applications,” Kerlin noted. “We recommend a hydraulic chuck or a high-precision collet chuck for finishing. Experience has shown us that for every tenth of an inch increase in runout at the nose, there’s a reduction in tool life of 10 percent. Your typical production toolholder will have low runout, high repeatability, and be extremely well balanced for high speeds.”

It all comes down to where the tool is going to be used, Pilger noted. Is it a dedicated application that is run every day? Or is it for a shop with many different types of jobs and materials?

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.

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.

“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.”

The T-A Pro, for example, conforms with a lot of the existing T-A GEN2 style of inserts and has carbide and high-speed steel options for higher penetration rates.

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.

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“In recommending the right drilling solution for its customers, we focus on metal-removal rate, how many cubic centimeters of metal are removed to keep our customers as productive as possible,” Hobbs said. Success is measured by the “cost-per-good-hole per component,” he said, for the best holes at the lowest cost for a specific application.

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.

“The main thing that helps our customers is the extra productivity from increased feed rate,” Ewing said. “If we’re cutting at five thou (thousand) per flute on a two-flute drill, we’ll be at 10 thou, but with a three-flute drill we’ll be at 15 thou per rev and that’s what increases feed rate and reduces cycle time. We typically see from 20 percent up to 50 percent reduction in cycle times with the LOGIQ3CHAM in production applications. In a job shop environment, depending on volumes, we might recommend staying with our regular exchangeable-head, two-flute SUMOCHAM drill,” he added.

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.

“The biggest challenge for our customers is making holes, good holes, as fast as possible, whether for difficult-to-machine materials like Inconel 718 for aerospace or 4140 steel for general engineering,” said Martin Hobbs, drilling and tapping product specialist at Sandvik Coromant US, Mebane, N.C. “It all comes down to the GD&T (geometric dimensioning and tolerancing) demands of the hole application. If we’re looking for looser tolerances say for bolt holes, we use indexable insert drills extensively, giving us the opportunity to punch holes very quickly at a very low cost. If you are looking for very tight tolerances under 2,000, that’s where we have to use solid-carbide drills to do that tight work,” Hobbs said.

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.

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.

“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.”

Big Daishowa’s new Nirox drill is a bridge between high-production and job-shop-type applications. Describing it as “remarkably tough,” Kerlin said the drill is designed for legacy machines that don’t have coolant-through and aren’t always stable. Nixrox uses coated carbide, flood coolant, and is available up to 9xD.

The most recent addition to Sandvik’s portfolio of solid-carbide drills and indexable and exchangeable-tip drills, the DS 20 insert drill is capable of 7xD drilling. Sandvik used new materials and technologies to develop a drill body and carbide to extend tool life while producing hole quality with more rigid material for deeper depths of cut.

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.

“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.”

“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.”

High-performance tools typically have a higher initial cost. But such tools may prove to be the less expensive option in the long run, asserted Jack Kerlin, applications engineer at Big Daishowa, Hoffman Estates, Illinois.

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.

“Most manufacturers have a variety of metric and inch drills in 3xD, 5xD, 8xD length off the shelf,” Pilger noted. “Carbide can run at higher speeds and handle heat much better than HSS, all major positives for increased production with lower tool costs. However, depending on the application, the brittleness of the carbide can work against you, causing tool breaks in poor unrigid setups for example.”

Emuge-Franken USA, West Boylston, Mass., emphasizes the importance of consistency and precise location of drilled holes. To increase tool performance and improve the quality of threads generated by its taps or thread mills, the company designs and manufactures a full line of high-penetration drills, featuring carbide grades with PVD-applied coatings,high-end hones, and flute forms and point geometries adjusted to fit the application.

Agreeing with his colleague, Ruegsegger noted Allied Machine serves both high-production shops and job shops. “Having a solution to meet all of their needs is the challenge; whether it’s how do we get the product out faster or whether it’s how do we quote these jobs to their customers and be cost efficient. We’re trying to find the best cost per hole for them to be able to offer to their customers as well,” he said.

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.

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.

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.

Iscar USA, Arlington, Texas, added a third flute to create its new line of LOGIQ3CHAM exchangeable-head flute drills. “It’s a game changer,” asserted Craig Ewing, product specialist. “It’s more of a production tool with significant gains in productivity with the versatility of the exchangeable head drill, using either the regular drilling head or the flat-bottom head.”

Emuge-Franken also has developed a completely new drill, the MultiDRILL, which is a multipurpose, high-penetration rate drill that is suited for manufacturers that have limited quantity production runs or operate in a job shop environment with many materials, the company said. The MultiDRILL is made of a sub-micro grain carbide with an ultra-fine grain that is harder than conventional carbide grades used for drilling, while retaining the ability to withstand shock and chipping.

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.

The line expands on the replaceable tip concept introduced by Iscar several years ago as SUMOCHAM. It features through-coolant holes, and is available in 1.5xD, 3xD, 5xD, and 8xD drilling depths with round and flat shanks. Each body accepts five head sizes in the smaller diameters and 10 head sizes on diameters of 15 mm and larger.

Tough, difficult-to-machine alloys; includes Hastelloy, Inconel and Monel. Many are nickel-base metals.

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.

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.”

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.

The PunchDrill’s patent-pending geometry features an innovative chip breaker that produces short chips to control machining forces. Other features include newly developed surface treatments and a hard diamond-like coating to provide reliable chip removal and increased process reliability. The PunchDrill is available in drilling depth ranges up to about 8xD, the nominal diameter range from 0.129” to 0.472” (3.3-12 mm). Machining is done with a normal drilling cycle on CNC machines with cutting speeds and coolant pressures similar to conventional drilling.

Dimension that defines the exterior diameter of a cylindrical or round part. See ID, inner diameter.

“Our target demographic is mostly high-production shops which, in itself, is a subjective term depending on who you’re talking to,” Kerlin said. “A lot of times shops don’t consider the total production run when deciding on tooling and equipment. But ultimately your best option is the one that is most cost efficient, regardless of initial cost. That’s our focus.”

“Our newest T-A Pro is designed for a wider range of inserts per drill body compared to a lot of the high-penetration style tools,” Weniger said. “For different ISO grades, selections include carbide for the longer run jobs that the job shops have or a high-speed steel just for standard work, using a standard style insert for a few holes here and there. You kind of have both options to play with there and that makes sense.”

“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.

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.

Weniger, who is responsible for Allied Machine’s legacy tools (including the high-precision T-A and T-A Pro lines), noted the challenge in finding the best of both worlds.

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

“Anything under three-quarters of an inch and lower diameter, we can use solid carbide; exchangeable tip from 10 mm up,” Hobbs continued, noting the choice depends on dimensions and tolerances. “If I have a three-quarter-inch hole, I can use either an exchangeable-tip, an indexable, or a solid-carbide tool. It comes down to the customer’s requirement for hole tolerance and straightness, and diameter tolerance.”

“We want to be able to provide the complete solution for our customers whether it’s the automaker drilling thousands of holes a day or the mom-and-pop shop just trying to punch holes in oil field parts,” Ruegsegger said.

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.

“A lot of our customers, especially today, are looking for time-saving solutions to get products to their customers as quickly as possible,” said Bill Ruegsegger, product manager in charge of Allied’s high-penetration, higher-production style tools. “Our drills combine operations to create holes faster with better surface finishes, allowing our customers to move products through their operations faster,” he added.

To meet the variety in job shops, drilling offers the versatility of modular drills for various jobs and materials. “What’s nice about the modular drill is its flexibility,” Pilger continued. “Starting with a 10 mm diameter, our standard bodies will hold about six different diameters up to 10.4 mm on 3xD, 5xD, and 8xD lengths. And It’s very easy to change a tip geometry to cut steel, cast iron, and stainless.”

Of the three types of drills that YG-1 offers, one is solid carbide and two are insert drills. Solid-carbide drills called Dream Drills are available with and without coolant through and are material specific for alloys and carbon steel, stainless steel, and aluminum. Solid carbide is positioned at one end of the spectrum, exchangeable tip drills in the middle, and indexable drills at the other end, explained Jan Andersson, director product management-indexable inserts.

Exchangeable-tip drills are good choices above two thou in tolerance but under the 10 thou range. Anything under two thou it’s solid carbides, or we go into reaming if necessary for very tight hole tolerance.”

Solid-carbide drills are still the workhorse for high-production applications with indexable and replaceable carbide-tip tools providing exceptional performance if properly matched to the application. “Traditional solid-carbide drills represented a major advancement from HSS (high-speed steel), delivering higher feeds and speeds and greater accuracy in diameters from one to 20 mm,” said Steve Pilger, product manager-holemaking, YG-1 Tool Co., Vernon Hills, Illinois.

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.

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

Drilling is one of the fastest and most precise production methods to remove material. Each of the three principal types of drills—solid carbide, exchangeable tip, and indexable—delivers quality performance when matched to the right application, a process that starts with uncovering the answers to critical questions about the scope of the project.

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).

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.

“Replaceable insert-tip drills feature a geometry similar to or the same as solid carbide without the cost and logistics of regrinding carbide,” Andersson said. “The larger the drill, the more advanced toward the indexable side; the smaller the drill, the more advanced closer to the solid-carbide drill with replaceable-tip drills in between. If we’re looking at hole quality, surface finish, and dimensional tolerances, the solid-carbide Dream Drill is going to be superior; indexable-insert drills are especially effective in what I call a hole punch when you need to drill a hole quickly, clear the hole, and the tolerance isn’t as critical,” Andersson added.

Questions that need answering include variations of the following: What is the hole used for? How many holes? What is the tolerance? What is the diameter? What is the material? What is the toolholding? What kind of machine, (new, modern, legacy)? What about finishing?

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.

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.

The third flute resulted in LOGIQ3CHAM generating 50 percent more chips that had to be evacuated through smaller gullets. Iscar redesigned the cutting edge to curl the chip differently to facilitate evacuation.

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.

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.

“Our legacy products are tailored for the job shop market where these companies want high production to be able to run tools fast to process parts fast through their shop,” added John Weniger. “But shops don’t often have a lot of margin and a lot of wiggle room on price when it comes down to it.”

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

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.

“Work hardening is always a challenge in these materials, though a suitable coating and coolant-through to evacuate chips as quickly as possible help,” he continued. “For harder materials, a larger point angle, for example, 140° typically is used. The traditional point angle for drills is 118°, but this is largely a leftover from the days of manual machining. As materials have gotten tougher and drill point grinding has gotten more sophisticated, a larger point angle emerged as the standard because it’s more durable, more repeatable, and doesn’t walk as much.”

Allied Machine’s latest products provide a cost-effective, replaceable-tip solution to drilling holes in a wide range of materials, according to Weniger.

“That’s where we bring in the indexable drills. They have higher tolerances, we’re talking north of 10 thou of an inch for hole diameters,” Hobbs explained. “Where we have bolt holes or hole lightening pattern to put into a flange to lighten the material, this is where insert drills do very well; anywhere we’ll be doing boring or reaming holes also in some threading the holes.

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.

“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.