These CBN wheels for double-disc grinding are used on hard-to-grind materials in gear, pump, bearing and automotive component manufacturing.
Grinding wheels are generally labeled with a maximum safe operating speed. Don't exceed this speed limit. The safest course is not even to mount a given wheel on any grinder fast enough to exceed this limit.
Higher productivity. Finish hard turning can remove more material per machining operation than grinding. This can make hard turning up to 3 to 4 times faster when compared to cylindrical grinding. Feb 14, 2013 Hard Turning Versus Grinding. Hard turning is often considered a replacement for grinding operations or as a pre-grinding process. Hard turning is often considered a replacement for grinding operations or as a pre-grinding process. It is most often performed on post-heat treated parts with surface hardness ranging from 45 HRC to 68 HRC or higher.
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The grinding wheel is a cutting tool. It's an abrasive cutting tool.
In a grinding wheel, the abrasive performs the same function as the teeth in a saw. But unlike a saw, which has teeth only on its edge, the grinding wheel has abrasive grains distributed throughout the wheel. Thousands of these hard, tough grains move against the workpiece to cut away tiny chips of material.
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Abrasive suppliers offer a wide array of products for a wide array of grinding applications in metalworking. Choosing the wrong product can cost the shop time and money. This article presents some of the fundamentals of selecting the best grinding wheel for the job.
Abrasives—Grits and Grains
Grinding wheels and other bonded abrasives have two major components-the abrasive grains that do the actual cutting and the bond that holds the grains together and supports them while they cut. The percentages of grain and bond and their spacing in the wheel determine the wheel's structure.
The particular abrasive used in a wheel is chosen based on the way it will interact with the work material. The ideal abrasive has the ability to stay sharp with minimal point dulling. When dulling begins, the abrasive fractures, creating new cutting points.
Each abrasive type is unique with distinct properties for hardness, strength, fracture toughness and resistance to impact.
Aluminum oxide is the most common abrasive used in grinding wheels. It is usually the abrasive chosen for grinding carbon steel, alloy steel, high speed steel, annealed malleable iron, wrought iron, and bronzes and similar metals. There are many different types of aluminum oxide abrasives, each specially made and blended for particular types of grinding jobs. Each abrasive type carries its own designation-usually a combination of a letter and a number. These designations vary by manufacturer.
Zirconia alumina is another family of abrasives, each one made from a different percentage of aluminum oxide and zirconium oxide. The combination results in a tough, durable abrasive that works well in rough grinding applications, such as cut-off operations, on a broad range of steels and steel alloys. As with aluminum oxide, there are several different types of zirconia alumina from which to choose.
Silicon carbide is an abrasive used for grinding gray iron, chilled iron, brass, soft bronze and aluminum, as well as stone, rubber and other non-ferrous materials.
Ceramic aluminum oxide is the newest major development in abrasives. This is a high-purity grain manufactured in a gel sintering process. The result is an abrasive with the ability to fracture at a controlled rate at the sub-micron level, constantly creating thousands of new cutting points. This abrasive is exceptionally hard and strong. It is primarily used for precision grinding in demanding applications on steels and alloys that are the most difficult to grind. The abrasive is normally blended in various percentages with other abrasives to optimize its performance for different applications and materials.
Once the grain is known, the next question relates to grit size. Every grinding wheel has a number designating this characteristic. Grit size is the size of individual abrasive grains in the wheel. It corresponds to the number of openings per linear inch in the final screen size used to size the grain. In other words, higher numbers translate to smaller openings in the screen the grains pass through. Lower numbers (such as 10, 16 or 24) denote a wheel with coarse grain. The coarser the grain, the larger the size of the material removed. Coarse grains are used for rapid stock removal where finish is not important. Higher numbers (such as 70, 100 and 180) are fine grit wheels. They are suitable for imparting fine finishes, for small areas of contact, and for use with hard, brittle materials.
Buying Bonds
To allow the abrasive in the wheel to cut efficiently, the wheel must contain the proper bond. The bond is the material that holds the abrasive grains together so they can cut effectively. The bond must also wear away as the abrasive grains wear and are expelled so new sharp grains are exposed.
There are three principal types of bonds used in conventional grinding wheels. Each type is capable of giving distinct characteristics to the grinding action of the wheel. The type of bond selected depends on such factors as the wheel operating speed, the type of grinding operation, the precision required and the material to be ground.
Most grinding wheels are made with vitrified bonds, which consist of a mixture of carefully selected clays. At the high temperatures produced in the kilns where grinding wheels are made, the clays and the abrasive grain fuse into a molten glass condition. During cooling, the glass forms a span that attaches each grain to its neighbor and supports the grains while they grind.
Grinding wheels made with vitrified bonds are very rigid, strong and porous. They remove stock material at high rates and grind to precise requirements. They are not affected by water, acid, oils or variations in temperature.
Vitrified bonds are very hard, but at the same time they are brittle like glass. They are broken down by the pressure of grinding.
Some bonds are made of organic substances. These bonds soften under the heat of grinding. The most common organic bond type is the resinoid bond, which is made from synthetic resin. Wheels with resinoid bonds are good choices for applications that require rapid stock removal, as well as those where better finishes are needed. They are designed to operate at higher speeds, and they are often used for wheels in fabrication shops, foundries, billet shops, and for saw sharpening and gumming.
Another type of organic bond is rubber. Wheels made with rubber bonds offer a smooth grinding action. Rubber bonds are often found in wheels used where a high quality of finish is required, such as ball bearing and roller bearing races. They are also frequently used for cut-off wheels where burr and burn must be held to a minimum.
The strength of a bond is designated in the grade of the grinding wheel. The bond is said to have a hard grade if the spans between each abrasive grain are very strong and retain the grains well against the grinding forces tending to pry them loose. A wheel is said to have a soft grade if only a small force is needed to release the grains. It is the relative amount of bond in the wheel that determines its grade or hardness.
Hard grade wheels are used for longer wheel life, for jobs on high-horsepower machines, and for jobs with small or narrow areas of contact. Soft grade wheels are used for rapid stock removal, for jobs with large areas of contact, and for hard materials such as tool steels and carbides.
Wheel Shapes
The wheel itself comes in a variety of shapes. The product typically pictured when one thinks of a grinding wheel is the straight wheel. The grinding face—the part of the wheel that addresses the work—is on the periphery of a straight wheel. A common variation of the straight wheel design is the recessed wheel, so called because the center of the wheel is recessed to allow it to fit on a machine spindle flange assembly.
On some wheels, the cutting face is on the side of the wheel. These wheels are usually named for their distinctive shapes, as in cylinder wheels, cup wheels and dish wheels. Sometimes bonded abrasive sections of various shapes are assembled to form a continuous or intermittent side grinding wheel. These products are called segments. Wheels with cutting faces on their sides are often used to grind the teeth of cutting tools and other hard-to-reach surfaces.
Mounted wheels are small grinding wheels with special shapes, such as cones or plugs, that are permanently mounted on a steel mandrel. They are used for a variety of off-hand and precision internal grinding jobs.
Tying It All Together
A number of factors must be considered in order to select the best grinding wheel for the job at hand. The first consideration is the material to be ground. This determines the kind of abrasive you will need in the wheel. For example, aluminum oxide or zirconia alumina should be used for grinding steels and steel alloys. For grinding cast iron, non-ferrous metals and non-metallic materials, select a silicon carbide abrasive.
Hard, brittle materials generally require a wheel with a fine grit size and a softer grade. Hard materials resist the penetration of abrasive grains and cause them to dull quickly. Therefore, the combination of finer grit and softer grade lets abrasive grains break away as they become dull, exposing fresh, sharp cutting points. On the other hand, wheels with the coarse grit and hard grade should be chosen for materials that are soft, ductile and easily penetrated.
The amount of stock to be removed is also a consideration. Coarser grits give rapid stock removal since they are capable of greater penetration and heavier cuts. However, if the work material is hard to penetrate, a slightly finer grit wheel will cut faster since there are more cutting points to do the work.
Wheels with vitrified bonds provide fast cutting. Resin, rubber or shellac bonds should be chosen if a smaller amount of stock is to be removed, or if the finish requirements are higher.
Another factor that affects the choice of wheel bond is the wheel speed in operation. Usually vitrified wheels are used at speeds less than 6,500 surface feet per minute. At higher speeds, the vitrified bond may break. Organic bond wheels are generally the choice between 6,500 and 9,500 surface feet per minute. Working at higher speeds usually requires specially designed wheels for high speed grinding.
In any case, do not exceed the safe operating speed shown on the wheel or its blotter. This might be specified in either rpm or sfm.
The next factor to consider is the area of grinding contact between the wheel and the workpiece. For a broad area of contact, use a wheel with coarser grit and softer grade. This ensures a free, cool cutting action under the heavier load imposed by the size of the surface to be ground. Smaller areas of grinding contact require wheels with finer grits and harder grades to withstand the greater unit pressure.
Next, consider the severity of the grinding action. This is defined as the pressure under which the grinding wheel and the workpiece are brought and held together. Some abrasives have been designed to withstand severe grinding conditions when grinding steel and steel alloys.
Grinding machine horsepower must also be considered. In general, harder grade wheels should be used on machines with higher horsepower. If horsepower is less than wheel diameter, a softer grade wheel should be used. If horsepower is greater than wheel diameter, choose a harder grade wheel.
Care And Feeding
Grinding wheels must be handled, mounted and used with the right amount of precaution and protection.
They should always be stored so they are protected from banging and gouging. The storage room should not be subjected to extreme variations in temperature and humidity because these can damage the bonds in some wheels.
Immediately after unpacking, all new wheels should be closely inspected to be sure they have not been damaged in transit. All used wheels returned to the storage room should also be inspected.
Wheels should be handled carefully to avoid dropping and bumping, since this may lead to damage or cracks. Wheels should be carried to the job, not rolled. If the wheel is too heavy to be carried safely by hand, use a hand truck, wagon or forklift truck with cushioning provided to avoid damage.
Before mounting a vitrified wheel, ring test it as explained in the American National Standards Institute's B7.1 Safety Code for the Use, Care and Protection of Grinding Wheels. The ring test is designed to detect any cracks in a wheel. Never use a cracked wheel.
A wise precaution is to be sure the spindle rpm of the machine you're using doesn't exceed the maximum safe speed of the grinding wheel.
Always use a wheel with a center hole size that fits snugly yet freely on the spindle without forcing it. Never attempt to alter the center hole. Use a matched pair of clean, recessed flanges at least one-third the diameter of the wheel. Flange bearing surfaces must be flat and free of any burrs or dirt buildup.
Tighten the spindle nut only enough to hold the wheel firmly without over-tightening. If mounting a directional wheel, look for the arrow marked on the wheel itself and be sure it points in the direction of spindle rotation.
Always make sure that all wheel and machine guards are in place, and that all covers are tightly closed before operating the machine. After the wheel is securely mounted and the guards are in place, turn on the machine, step back out of the way and let it run for at least one minute at operating speed before starting to grind.
Grind only on the face of a straight wheel. Grind only on the side of a cylinder, cup or segment wheel. Make grinding contact gently, without bumping or gouging. Never force grinding so that the motor slows noticeably or the work gets hot. The machine ampmeter can be a good indicator of correct performance.
If a wheel breaks during use, make a careful inspection of the machine to be sure that protective hoods and guards have not been damaged. Also, check the flanges, spindle and mounting nuts to be sure they are not bent, sprung or otherwise damaged.
System Analysis
The grinding wheel is one component in an engineered system consisting of wheel, machine tool, work material and operational factors. Each factor affects all the others. Accordingly, the shop that wants to optimize grinding performance will choose the grinding wheel best suited to all of these other components of the process.
About the author: Joe Sullivan is senior product manager for Norton Company, Worcester, Massachusetts.
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Requirements for milling hardened steels
By Kip Hanson
Click Here for a free subscription to Cutting Tool Engineering magazine.
Doing it the Hard Way
Requirements for milling hardened steels.
Thinking about taking the leap into milling hardened steels? Why would you? After all, if your shop has been successfully grinding, jig boring and EDMing hardened materials, why change?
For starters, hard milling might be more profitable. Michael Minton, national application engineering manager for Methods Machine Tool Inc., Sudbury, Mass., explained that hard milling not only eliminates costly finishing operations, but produces a higher quality part than does traditional machining methods.
Courtesy of Greenleaf
Roughing hardened tool steel with a facemill tooled with ceramic inserts.
“By machining after heat treatment, you not only avoid secondary operations, but also eliminate problems with workpieces being twisted, bent or otherwise out of shape due to heat treating,” Minton said. “This allows you to make a part with higher accuracy and better dimensional characteristics compared to parts heat-treated after machining.”
In general, hard milling involves cutting primarily tool steel or precipitation hardening stainless steel, such as 15-5 or 17-4, that has been hardened to at least 50 HRC. After a workpiece is roughed in the soft state, it is sent to the furnace for hardening and then finish machined with coated carbide, ceramic or PCBN tools. The amount of metal removal in the hardened state is minimal—perhaps just 0.010 ' to 0.020 ' per surface—making this process feasible for most hardened parts.
Depending on the workpiece configuration, production volume and amount of stock removal, however, it may be feasible to machine the workpiece entirely from a hardened state. Modern machine tools, advanced cutting tool materials and sophisticated CAM programs make what was once a highly improbable machining operation into one within the reach of many shops. According to Minton, the advantage of machining from a hardened state is having to cut it only once.
Good Machines
However, you’re not going to accomplish this on an old knee mill. “As always, machine tool construction plays a large part in the level of success you’ll achieve with hard milling,” Minton said. “You can be successful with linear way machines, provided they are made well.”
Another key is spindle design and construction. “That’s the only thing holding the tool and keeping it stable, so very solid, HSK-capable spindles typically are required,” he added.
Minton noted that volumetric accuracy is also important. What does accuracy of the machine tool have to do with cutter life? “Because of the need for consistent chip loads and predictable stock removal, the more square the spindle is to your workpiece, the better your tool life.”
Danny Haight, national milling product manager for Mitsubishi machine supplier MC Machinery Systems Inc., Woodale, Ill., agreed. “You need a solid machine tool, one with bridge construction and a rigid spindle. You also need hand-scraped machine surfaces because they are more accurate and better at dampening vibration than conventionally ground surfaces.”
Of course, the level of machine rigidity depends on what type of hard milling you’re doing. “There’s a big difference between the cutting forces generated when finish machining a mold for a hearing aid vs. roughing a mold cavity for a telephone or an automobile turn signal lens,” Haight said. “Bigger DOCs mean higher cutting forces, which in turn require a more rigid machine tool.”
Haight explained that because of the demanding toolpaths required for typical hard milling jobs—3-D contouring consisting of many short, high-speed movements designed to deliver consistent cutter engagement—the machine controller is also very important.
He said: “The control should have good look-ahead capabilities and fast calculation times. The machine should be very responsive when changing directions or going in and out of corners. You need to maintain a constant chip load if you want your cutters to last.”
Tough Tools
When milling materials from 50 to 60 HRC, not just any cutter will do. Not only is the workpiece very hard, but to reduce thermal fluctuations on the cutting tool, machining is typically done dry. For this, you need tough tools.
One company offering such tools is SGS Tool Co., Munroe Falls, Ohio. Product Manager Jason Wells said SGS’ Z-Carb MD solid-carbide endmills are designed for hard milling, including a negative rake to strengthen and support the cutting edge, an AlTiN coating for heat resistance and an eccentric relief with a radial grind to also strengthen the cutting edge.
Courtesy of Makino Inc.
Hard milling miniature mold cavities.
“Due to the high level of energy needed to create a chip in hardened steels and the abrasive action of the workpiece, you need a tool with a lower-volume cobalt and fine-grain substrate to endure the high loads and temperatures seen in dry machining,” he added.
Coated carbides offer a good trade-off between heat and wear resistance and between strength and toughness, according to Wells. “It’s all about compromise. Ceramics and PCBN definitely have good heat and wear properties, but are more fragile when it comes to shock and imperfect cutting conditions.”
Applications Engineer Dale Hill of Greenleaf Corp., Saegertown, Pa., concurred. “Ceramics don’t do well in situations where you have vibration, excessive tool overhang and less-than-rigid spindles or fixtures. Failures in ceramics are generally mechanical in nature.” Even under normal milling conditions, the ceramic tool flexes as it enters and exits the cut. “It’s unavoidable,” he said. “This flex causes chipping of the cutting edge at a microscopic level. What appears as flank wear is actually microchipping caused by deflection and forces on the tool; as the microchips propagate, the tool eventually fails.”
Despite this, however, ceramics are widely applied for milling hardened steels, irons and superalloys. That’s because carbide’s cobalt binder begins to soften at around 1,600º F, while ceramics can operate effectively at temperatures up to about 4,000º F. “Ceramic comes in where carbide leaves off,” Hill said, explaining that the higher the hardness, the more heat generated during machining.
Courtesy of SGS Tool
Three-dimensional contouring of hardened steel using a ballnose endmill.
Because of this, ceramics can successfully machine into HRCs in the mid-60s. “We’ve even pushed into the high 60s,” Hill said. “Because ceramic is indifferent to heat, cutting speeds can be much higher. In many cases, carbide’s toughness allows a higher chip load per tooth, but the significant speed increase offered by ceramic offsets that higher feed rate. In most cases, ceramic tools will produce much higher metal-removal rates.”
It comes down to economics because a high-quality carbide insert might cost $7 to $8 compared to $20 for a ceramic one. And when the insert costs nearly three times as much, you have to ask if it can remove at least three times as much metal. “The answer is generally yes, but you’ve got to weigh all the machining factors,” Hill said. These include insert life, the cost of the inserts, time to change out a worn set of inserts, required part accuracy and machine capabilities. “It’s all about total metal removal.”
Geometries at Work
As with carbide, toolmakers change the geometry of a ceramic tool for cutting hardened materials. Hill is a strong believer in positive geometry tools for softer materials, where built-up edge can be an issue. “Chip flow is critical when you’re under 45 HRC. But as the hardness goes up, we go to negative tools. We don’t have BUE problems with hard machining.”
Courtesy of Surfware
Constant cutter engagement is critical in hard milling operations.
When hard milling, it’s important to avoid shocking the tool, especially a ceramic one. This can be accomplished by reducing the feed rate on entry and exit, taking a circular toolpath into the workpiece and ramping into pockets and cavities. CAM systems do this automatically, according to Hill.
As proof, he related a story about a WESTEC show where he’d been struggling with tool life during a hard milling demo. “One of the CAM guys came over from a neighboring booth and offered to reprogram our toolpaths,” Hill said. “When he was done, tool life went from 15 to 20 minutes all the way up to an hour.”
Hill attributed this success to better control of tool engagement and adjusting for chip thinning. “You need to maintain a constant average chip thickness, and chip thinning can occur if the radial and axial cutter engagement of the cutter decreases,” he said. “As the chips get thinner, you need to increase the feed rate to compensate. Otherwise, you’ll end up rubbing the cutter to death.”
When cutting steels harder than 65 HRC, coated carbides are used with limited success. Ceramics do a decent job if the DOCs are decreased appropriately. But, according to Gabriel Dontu, global superhard technical leader for Kennametal Inc., Latrobe, Pa., PCBN easily cuts hardened steels up to 68 HRC and can cut materials as hard as 78 HRB. PCBN is twice as hard as any ceramic or carbide material. The trade-off is toughness—the harder the cutter, the less tough it is. This limits the application of PCBN, especially on interrupted cuts.
“PCBN is a composite material, made of cubic boron nitride particles mixed with a binder,” Dontu said. “It is created under volcanic-type temperatures and pressures—imagine a three-story tall press pushing on a tube the size of a tennis ball.” About 90 percent of commercial PCBN is made into disk-shaped wafers, up to 100mm in diameter and 3.2mm thick, which are then sliced into segments and brazed onto a carbide substrate.
Courtesy of Greenleaf
Indexable ceramic cutters suitable for hard milling.
This complex process limits the geometries of PCBN tools to relatively simple shapes while also making them costly. PCBN can cost 10 times as much as comparable ceramics and carbides. However, PCBN tool life is up to five times higher, according to Dontu.
How is 10 times the cost but only five times the life justifiable? “PCBN allows you to hold very tight tolerances with minimal wear,” Dontu said. “This means that, for example, on large molds you can machine the entire cavity with a single PCBN tool and avoid having to blend in the middle of a cut after a tool change.”
Like ceramics, PCBN tools are presented at a negative angle to the workpiece. Edge prep is paramount with PCBN, and a K-land or T-land is ground on the tool, depending on the operation. Unfortunately, PCBN tools also suffer some of the same failure modes as ceramics. They work best under rigid, predictable cutting conditions, and lack toughness compared to carbide. For this reason, they are typically used only for finishing, and are reserved for the most demanding applications, such as extremely hard machining, tight-tolerance requirements and long production runs.
Taking the Right Path
As with other machining operations, even the best cutting tool will fail when hard milling if it’s not programmed correctly. Unlike CAM programming for softer materials, where cutting parameters are typically broad and more forgiving, machining hardened workpieces requires predictable and consistent toolpaths. One company specializing in toolpath generation for hard milling is Surfware Inc., Camarillo, Calif.
“Precisely controlling the engagement angle of the cutter throughout the toolpath is the key to increasing tool life, because the engagement angle determines how long the tool tip is in contact with the material,” said Alan Diehl, CEO of Surfware. “The greater the angle, the longer the tool is engaged and the greater the amount of heat inflicted on the tool.”
According to Diehl, Surfware’s Surfcam controls the engagement angle automatically, thus reducing tool temperature while increasing tool life and the mrr. This becomes even more important when machining hardened materials where, as engagement increases, cutting-edge temperatures increase exponentially.
Delcam Inc., Salt Lake City, is another software developer promising better toolpaths for hard milling. Mark Cadogan, vice president of sales for Delcam, said, “We use a patented point-distribution technology that reduces sharp angle changes while still providing constant cutter loads.” The technology allows the programmer to input and automatically distribute as many points as desired, and the software will then drive the cutter through those points in the most accurate way possible, according to Cadogan. “This is great for machines that can handle high amounts of data, and works especially well for detailed 3-D surfaces in hardened steels.”
Although it’s probably best to hang onto that grinder, jig borer or EDM your shop uses for cutting hardened steels just in case, milling those materials instead can provide numerous benefits when the process is understood and proper tools, equipment and software are in place. CTE
About the Author: Kip Hanson is a manufacturing consultant and freelance writer. Contact him by phone at (520) 548-7328 or e-mail at [email protected].
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Hard milling: Bringing it all back home
Hard Milling Solutions Inc., Romeo, Mich., regularly hard mills plastic injection molds, tooling for the can industry, forging dies and other workpieces that can exceed 60 HRC. “We cut as hard as anybody out there,” said owner Corey Greenwald. The shop not only cuts hard, but competitively, and is seeing jobs once lost to China returning.
The process varies depending on the workpiece. “We make some 5 '×5 ' forging dies out of 50-HRC H-13 tool steel. We purchase the raw blanks, send them out for heat treatment, then rough and finish mill, drill and thread mill the holes, all from the hardened state.”
Deciding whether to rough in the hardened state or not depends primarily on the volume of material removed. “If I have a workpiece where I’m removing more than 30 percent of the blank, I’ll usually rough it soft, heat-treat and then finish machine in the hardened state,” Greenwald said. This is especially true on anything above 55 HRC. “It’s almost like trying to cut carbide with carbide. You want to bring it as close to the finished size as possible beforehand to avoid that problem.”
Hard Milling Solutions primarily applies coated carbides, as well as some PCBN tools for finishing work, especially on more abrasive workpiece materials such as hardened tool steels. The shop routinely holds tolerances as tight as +0.0002 '/ -0.0000 '. “We’re doing work that previously would have been done on a jig grinder.”
Sound tough? It gets tougher. Most of a typical job is performed unattended. “Walk out to our shop floor and you’ll see there’s nobody standing in front of the machines. We were one of the first in the country to do this, and when we started out, the knowledge wasn’t available,” Greenwald said. “The key is not just the hard milling—it’s the data. You need to collect the data and save it to a database, so you can cut lights out even on hardened materials.”
The shop has 46 ' Samsung TVs on the wall showing live video from inside the machines. “We run one shift. At night, the machine can text message the operator at home if there’s a problem, and he can then remotely access the machine, take control, go to the alarm screen, correct the program and change tools.
“It’s not rocket science, but it’s a lot closer to it now than it used to be,” Greenwald continued. “As the part materials get harder, all the forgiveness goes away. You have to do everything right—toolpaths, cutters and equipment. You make a mistake, and you’re going to smoke your cutter the instant it hits the part. Worse, you might burn up a $30,000 spindle.”
In addition to the machine, peripherals such as lasers, probes and software are also critical to hard milling. With this technology and highly skilled machinists, Greenwald finds that many jobs previously sent overseas are coming back.
“We’re competitive with China,” he said. “What used to take 20 hours of manual labor can now be done in a little over an hour. It’s not about throwing a bunch of people at it anymore.”
—K. Hanson
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Contributors
Delcam Inc.
(877) DELCAM
www.delcam.com
Greenleaf Corp.
(800) 458-1850
www.greenleafcorporation.com
Hard Milling Solutions Inc.
(586) 336-9737
www.hardmillingsolutions.com
Kennametal Inc.
(800) 446-7738
www.kennametal.com
MC Machinery Systems Inc.
(630) 860-4210
www.mcmachinery.com
Methods Machine Tools Inc.
(877) 668-4262
www.methodsmachine.com
SGS Tool Co.
(330) 688-6667
www.sgstool.com
Surfware Inc.
(818) 991-1960
www.surfware.com
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