Behind the Carbide Curtain

Carbide-tool grades are not standardized. The ISO system and the “C” system both offer individual manufacturers’ recommendations for applications, but neither of them sets minimum requirements for the carbide’s composition, properties, or performance. Is this good, bad, or irrelevant? It depends on whom you talk to.

Tool producers will tell you that today’s carbide tools—with their vast array of compositions and coatings—are too complex to be covered by an all-encompassing standard. Certainly, the explosion of coatings in recent years (it’s estimated that 80% of carbide tools sold today are coated) has complicated tool classifications. And coatings are no more standardized than substrates.

Tool producers will further tell you that the current grading systems are adequate for most users’ purposes. Some carbide-tool users, however, disagree, arguing that the lack of a carbide standard plays directly into the hands of the carbide-tool producers by making it extremely difficult to switch from one brand’s carbide grade to another brand’s equivalent. A C-5 carbide tool from Producer A may vary drastically from Producer B’s C-5 tool. The systems tell users what inserts of a given classification should be used for, but they fail to describe the criteria for classifying carbide grades. The ISO and C systems leave users dependent upon the producers’ judgments of what grades are suited for a particular application, judgments that may or may not be based on sound analysis of a carbide grade’s properties and cutting characteristics. The end result, these users say, is a costly, time-consuming reliance on trial-and-error to determine the best tool for a given job.

 

Despite official and unofficial “standards,” the true nature of carbide grades—how they’re made and what they’re made of—remains shrouded in mystery.

Some users have called for a descriptive standard that would delineate minimum requirements in terms of compositions and properties a carbide material would require to be given a certain classification. The standard could still be used to prescribe certain uses for certain classifications, but users would be guaranteed that the tools met certain criteria other than the manufacturer’s opinion of how they should be used. Meeting certain physical criteria would also ensure a level of consistency from brand to brand that is currently lacking.

The First Standards
In its early years, carbide was a relatively simple material and, hence, easy to standardize. Sintered tungsten carbides for cutting tools were first introduced by Fried. Krupp of Germany in 1927 under the name Widia (wie Diamant—like diamond). During World War II, sintered-carbide development advanced rapidly in Germany, spurred by a tungsten shortage. Since tungsten in carbide cuts metal more efficiently than tungsten in high-speed steel, the Germans used cemented carbides for metalcutting wherever possible.

After the war, Allied investigators published detailed accounts of Krupp-Widia carbide compositions, production techniques, quality-control methods, and related research projects. This information formed the basis of an ersatz European standard. Continuing efforts to replace tungsten with less expensive materials led to a flood of carbide formulations based on materials such as titanium and tantalum. As a result, the neat, orderly German standard of tungsten-base grades was rendered obsolete. Nevertheless, the Krupp-Widia standard formed the basis for a system adopted by DIN, the German standards organization, based solely on application recommendations. The DIN system eventually was adopted as the ISO coding system we know today.

In the United States, Oscar Strand of the Buick Motor Division of General Motors developed an applications-based classification code for nearly 100 grades in 1942. The grades were arranged into a simple system of only 14 symbols. This code evolved into the familiar “C” code, which became the unofficial American standard. While Buick went on to standardize carbide tools according to testable properties—such as chemical composition, tensile strength, compressive strength, thermal conductivity, density, average grain size, and grain-size distribution—the C code as embraced nationwide was based solely on manufacturers’ application recommendations and had no meaning in terms of testable properties.

Later, the U.S. Department of Defense (DOD) attempted to rectify this situation by pressuring carbide-tool manufacturers to adopt a more descriptive system for government procurement. While the DOD’s earlier attempts to standardize tool steels had at least partially succeeded, its efforts to standardize carbide failed.

“Carbides weren’t standardized the way tool steels were because the DOD didn’t know enough about the subject to push the carbide-tool producers into a corner,” asserts Kenneth Brookes, proprietor of International Carbide Data, East Barnet, England, and author of World Directory and Handbook of Hardmetals and Hard Materials (now in its sixth edition). “The DOD told tool-steel manufacturers that it wanted a standard and wouldn’t buy anything that didn’t meet that standard. They couldn’t do that with the carbide manufacturers, who told them that standardization would stifle carbide research and development.”

The C code held sway in the United States until the late 1980s, when the American National Standards Institute (ANSI) adopted the ISO coding system—though references to C-code classifications are still used informally and are, for most end users, still more easily recognizable. In practical terms, this move changed only the symbols used to codify carbide grades and the workpiece-material categories, not the basic concept of classifying carbide prescriptively rather than descriptively.

The Current Standard
The ISO code has been given a higher profile by several major carbide-tool producers’ adoption of the ISO color-coding system. The ISO grade for a given material is defined in the document ISO 513-1975E (Table 1). The ISO code is divided into three broad letter-and-color classifications: P (blue) is for highly alloyed grades to cut long-chipping steels; M (yellow) is for lesser alloyed grades to cut ferrous metals with long or short chips and nonferrous metals; and K (red) is for straight tungsten-carbide grades to cut short-chipping gray cast irons, nonferrous metals, and nonmetallic materials. The workpiece categories are arranged according to chip-producing characteristics and certain metallurgical characteristics such as casting condition, hardness, and tensile strength. Under the ISO system, both steels and cast irons can be found in more than one category based on their chip-formation characteristics. Each carbide grade within a classification is given a number to designate its position in a continuum ranging from maximum hardness to maximum toughness. A proposal to add a suffix to indicated a coated grade was dropped; it made no sense, given the fact that the ISO standard describes applications, not tools, and an application can’t be coated.

The first U.S. carbide-tool manufacturer to adopt the ISO color code was Carboloy Inc., a Seco Tools company, Detroit. “We adopted the Secolor system to help simplify grade selection for our customers,” says Debbie Svennevik, Carboloy’s manager of quality manufacturing. “Since then, many of our main competitors have realized the value of this system and have sought to emulate it.”

According to Jim Ther, project engineer with Valenite Inc., Troy, MI, his company modified their use of the ISO color codes to define the three categories more clearly. In Valenite’s system, blue is for free-machining steels, carbon steels, tool steels, and alloy steels; yellow is for stainless steels and high-temperature nickel- and cobalt-base alloys; and red is for gray cast irons, ductile or nodular irons, malleable irons, aluminum and copper alloys, plastics, and nonmetallic materials.

Sandvik Coromant Co., Fair Lawn, NJ, has introduced the CoroKey system, which employs a simplified version of the ISO color designations (blue is for steel, yellow is for stainless steel, and red is for cast iron) but uses a different set of letter prefixes—R for roughing, M for medium machining, and F for finishing.

Kennametal Inc., Latrobe, PA, uses its own classification system. Notes Bernard North, Kennametal’s director, materials and process development, “We are concerned that, by trying to make the coding simple, you can end up misleading the customer. For example, stainless steels are treated as one material under these color codes. But there’s a tremendous variation between different kinds of stainless steels and their machining characteristics. It may well be that some stainless steels are best machined with a tool that would ordinarily be used on cast iron. The actual application ranges of our tools really don’t fit into a nice, neat split between workpiece materials. We have grades that are used successfully on gray cast irons, ductile cast irons, low-carbon steels, and stainless steels. How do you classify those grades according to the ISO system?”

Most carbide-tool manufacturers classify their products by subjecting the carbide material in question to performance tests run under a variety of conditions and parameters. To really understand the meaning behind a carbide-tool manufacturer’s grade determination, one must read the manufacturer’s literature carefully to see what it recommends in terms of machine type, speeds and feeds, workpiece materials, and maximum shock the tool can withstand.

But are these recommendations always trustworthy? “Sometimes the manufacturer isn’t very good at recommending,” asserts Kenneth Brookes. “Also, one manufacturer might make 20 different carbide materials, all of which it assigns to the P-20 category, while another manufacturer might make one grade that it recommends for everything.”

According to Valenite’s Jim Ther, the phenomenon of a manufacturer giving one carbide grade a range of classifications is due largely to advancements in coating technology. “As coating technology progressed, substrates that were specifically designed to accept a coating were developed. Often these substrates were suitable for machining more than one category of material. Today, there are many types of substrates—beta-free, cobalt-enriched, stratified-layer—and many multilayer coatings that allow even wider applications of a given carbide classification.”

With this lack of a one-to-one correlation between carbide materials and their classifications, combined with the subjectivity of the classification procedure, it’s no wonder that carbide tools of the same grade classification from different manufacturers can vary widely in characteristics and performance. “They can be as different as chalk and cheese,” says Brookes. “The fact that two brands have the same code doesn’t mean anything. They could have completely different compositions and properties. I did an analysis once for a conference and I found that M-20 carbide grades from various manufacturers covered every conceivable type of carbide. The only thing they had in common was that they all contained carbon. Some were based on titanium carbide and some on tungsten carbide. Some had a nickel or nickel-molybdenum binder, while others had a cobalt binder.”

The result can be widely varying performance between brands. “Competitive brands of the same classification may be manufactured differently with different specifications and raw materials made available with different grain sizes, and as a result they may differ dramatically in performance. That’s the weakness of the ISO grading system,” says Steve Abrams, president of Hanita Cutting Tools Inc., Mountainside, NJ, a company that does not sinter its own carbide but rather purchases sintered blanks. However, Henry Scussel, manager of the performance and technical-support group at Valenite, states that uncoated grades of the same designation tend to be chemically and metallurgically alike from manufacturer to manufacturer: “We feel the real differences between uncoated brands lie in the manufacturer’s ability to make its grade with a minimum of variation day in and day out, batch after batch.” With coated grades, the problem becomes more complex. “Performance differences between coated grades are due to the manufacturer’s understanding of applications, insert geometries, substrate metallurgy, coating technology, edge preparation, chipbreaker/top-form configurations, and all the interactions between these factors,” Scussel notes.

 

Symbol Broad Category of material to be machined Distinguishing color Designation Material to be machined P Ferrous metals with long chips BLUE P-01 Steel, steel castings P-10 Steel, steel castings P-20 Steel, steel castings, malleable cast iron with long chips P-30 Steel, steel castings, malleable cast iron with long chips P-40 Steel, steel castings with sand inclusion and cavities P-50 Steel, steel castings of medium or low tensile strength, with sand inclusion and cavities M Ferrous metals with long or short chips and nonferrous metals YELLOW M-10 Steel, steel castings, manganese steel, gray cast iron, alloy cast iron M-20 Steel, steel castings, austenitic or manganese steel, gray cast iron M-30 Steel, steel castings, austenitic steel, gray cast iron, high-temperature-resistant alloys M-40 Mild free-cutting steel, low-tensile steel, nonferrous metals and light alloys K Ferrous metals with short chips, nonferrous metals, and nonmetallic materials RED K-01 Very hard gray cast iron, chilled castings of over 85 shore, high-silicon-aluminum alloys, hardened steel, highly abrasive plastics, hard cardboard, ceramics K-10 Gray cast iron over 220Bhn, malleable cast iron with short chips, hardened steel, silicon-aluminum alloys, copper alloys, plastics, glass, hard rubber, hard cardboard, porcelain, stone K-20 Gray cast iron up to 220Bhn, nonferrous metals: copper, brass, aluminum K-30 Low-hardness gray cast iron, low-tensile steel, compressed wood K-40 Soft or hard wood, nonferrous metals Table 1: ISO 513 classifications of cutting tool material applications.

Making the Grade
Most carbide compositions involve basically four components: tungsten carbide, tantalum/niobium carbide, titanium carbide, and cobalt. Each of these is added to give the cutting tool a specific characteristic: strength, toughness, wear resistance at low temperature, chemical wear resistance at high temperature, or resistance to deformation at high temperature. Unfortunately, each of these raw materials brings several undesirable properties along with the good. All carbide compositions therefore constitute trade-offs of physical or mechanical properties. The more complex the composition, the more variable the percentages of cobalt and additives within that grade.

Grain size also varies greatly within a given grade. And it’s a variable that has a profound effect on the carbide tool’s performance. As carbide grains get coarser, the material gains toughness and shock resistance while losing hardness. But if grain size is inconsistent, the results can be devastating. An unusually large grain acts as a void in the carbide and makes the tool more likely to break in use, because it concentrates stresses at that point. These large grains develop at the sintering stage. When carbide is sintered, a lot of it dissolves in the cobalt binder at the sintering temperature. Then, as the material cools down, the carbide comes out of solution and precipitates back onto the original grain. However, if the carbide powder consists of varying grain sizes, the finest grains will disappear altogether while the coarsest grains become even coarser during sintering. “If all the grains are the same size, then this won’t occur,” says Kenneth Brookes. “But if you start with irregular grain sizes, then you will wind up with a fairly coarse sintered product having gigantic 20µm to 30µm grains—usually described as ‘footballs.’ A tool made of material containing these large grains can break quickly, so you have to be very conservative with the stresses you put on it.”

Some carbide-tool suppliers are better at maintaining tight control of post-sintering grain size than others, in part because of the various processing techniques employed by the raw-material producers. But the processes that produce the most consistent grain sizes are also the most expensive, and that expense hikes up the cost of the materials. Since most carbide-tool producers use the same basic sintering technology, grain-size control depends mainly on the raw materials. Raw-material-procurement strategies vary: Some companies produce their own raw materials, some have one supplier, and others tap into various suppliers.

Test Grades
Each of the carbide-tool producers interviewed reports that it performs acceptance testing of incoming carbide powders. Typically, tool producers perform tests on raw materials by combining a small sample of grade powder with cobalt, pressing and sintering test bars, and then evaluating the bars’ porosity, microstructure, post-sintering carbon content, and magnetic properties. Sometimes materials are tested in powder form for flow and bulk density. Generally, more advanced materials require more frequent sample analysis of microstructure.

In an effort to ensure quality and reassure end users, carbide-tool manufacturers employ SPC and quality checks throughout tool production. Kennametal, for example, employs SPC in its sintering processes, using in-house standards to make sure that the sintering furnace is operating properly. The standards are designed to be overly sensitive, so that problems can be detected before they begin affecting the end product. Checks are done by sintering samples along with the main production run. There are in-house specifications for composition, hardness, magnetic saturation (a measure of the composition of the intergranular phase, or the cobalt binder), coercive force (which correlates with toughness), and coating thickness.

Carbide-tool producers are beginning to use new tools to make these measurements. “We still do some of the metallographic work with old-fashioned microscopes,” says Carboloy’s manager of metallurgical processes, Vic Bruni. “But we also use optical light-image analysis, X-ray diffraction, and other instruments and technologies that are relatively new to the industry.” Bruni says that these new instruments have played a key role in boosting tool consistency.

But do all carbide-tool producers adequately test incoming raw materials? Some users think not. Says Joe Peluso, manager (retired) with Boeing Co., Seattle, “At Boeing, we found, not surprisingly, that those people who tested their carbide seemed to provide better consistency than those who didn’t. It was like the old coffee advertisement—‘If we don’t buy these coffee beans, someone else will.’ So the people who do not conduct tests are probably getting contaminated carbide that someone else rejected.”

Hanita’s Steve Abrams offers these words of caution regarding tool producers’ incoming raw materials: “It’s easy to buy cheap carbide. Unfortunately, I think there is a lot of that in the market. As a result, you can buy carbide tools that are very inexpensive. And the performance of those tools—sometimes it’s good; sometimes it’s horrendous. That reflects the inconsistency of the raw materials. The top companies are doing their own in-house inspection and they are, in fact, rejecting raw materials.”

What’s the Problem?
Carbide-tool producers argue that improved production techniques and rigorous quality checks ensure a relatively consistent product. Inconsistent carbide-tool performance, they say, often is a reflection of workpiece-material inconsistency or machining parameters rather than of the tool itself. “The carbide insert is always the primary suspect when a performance problem comes up,” says Valenite’s Henry Scussel. “But the chief factor in performance variation in our products is variation in the workpiece material’s machinability.”

Workpiece variation can occur from one shipment of metal to the next from the same supplier, but it occurs even more frequently when shops change casting suppliers. The new suppliers may have different means of processing the metal, may use different compositions, or may supply metal more prone to nodules and other irregularities.

According to Ed Hermsen, manufacturing engineer, John Deere Engine Division, Dubuque, IA, workpiece variation is a common problem for John Deere. “Even with the tight, detailed specifications we have for our workpiece materials, there can be a lot of chemical variation within a specification,” he says. “A small increase in sulfur content can make something more machinable, while a slightly higher chromium content can cause problems. Within a spec, you can still see variation that causes you grief.

“Our workpiece-material tolerances are much tighter than a lot of our competitors’. Yet even our material classification is wide enough that we can experience a difference of RC 5 within a spec. And the allowable variations in chemical compositions can make carbide behave differently from one batch of parts to another. There’s no way that you can have a tool that performs as well at RC 25 as at RC 30. Your chip-control problems are totally different from one to the other.”

In some cases, neither the tool nor the workpiece is the culprit—a change in machining parameters may be the cause of inconsistent tool life. “Often the problem is something that changed in the end users’ process parameters, and it can only be corrected by the analysis and adjustment of those parameters,” says Carboloy’s Debbie Svennevik.

Producers’ Choice
A descriptive carbide standard that imposes minimum requirements for a given carbide classification might ensure a level of tool consistency and help isolate workpiece-related or machining-parameter problems. Nevertheless, the current ISO-based code and the C code get staunch support from most major carbide-tool producers. Why? According to many of these producers, carbide tools have simply become too complex for true standardization and will become increasingly complex in the future.

“The problem is that if you tried to make the standard sufficiently all-embracing, it would become so complex that it wouldn’t be very helpful,” insists Kennametal’s Bernard North. “Today, the tool is so much more sophisticated. We have cobalt enrichment, magnetic-saturation control, coatings, different edge preparations, and chipbreaker geometries. You can have a tough or a fine chipbreaker geometry, you can have a tough or a fine grade, you can have various coating thicknesses. It’s very difficult to really describe these things adequately with a standard. It’s a complex system with at least four variables—substrate, coating, edge preparation, and macrogeometry—that all contribute to how suited this tool is to fine cutting or rough cutting.”

Dave Watson, director of quality with Sandvik, suggests that continuing development of coated grades to machine newer workpiece materials makes standardization tougher than ever. “As coating technology evolves, new substrates are being designed as well to improve coating performance, such as cobalt-enriched layers. I think if you tried to establish a true standard, it might be too general to be meaningful. And the standard would be constantly changing, because you’d have to keep incorporating the latest developments.”

But there may be other motivations for maintaining the current grading codes. Carbide-tool producers are notoriously secretive, and understandably so—the number of major producers is few and the competition ferocious. There seems to be little motivation to share the information needed to fashion a descriptive carbide-tool standard. As Carboloy’s Vic Bruni puts it, “The highly competitive nature of this business, coupled with the fact that the technology changes rapidly, inhibits the free and open discussion that is essential for creating industry standards. How can you have that kind of discussion when each participant needs to protect his or her company’s most closely held secrets?”

Further decreasing the likelihood of a voluntary, industrywide standard is the carbide-tool producers’ seeming dislike for one another. “They don’t get together at a meeting someplace and sit down to try to make their product line better,” says Joe Peluso. “The idea of working with their competitors is not part of their thinking process.”

Most carbide-tool producers will disclose composition data to an end user, if the end user is important enough to them. For the most part, though, tool producers believe that the end user wouldn’t know what to make of the information if it were provided. Indeed, with no descriptive standard in place, this is probably true in most cases.

“They all want to make sure that their widget is just a little different from everyone else’s, or at least that it’s perceived as being different,” opines Lynn Engelhuber, tool-management leader with General Motors Powertrain Division, Pontiac, MI.

From the end users’ perspective, it seems that motivation to develop a descriptive standard will have to come from outside the carbide-producing community. “At Boeing, we told our suppliers that they’d have to adhere to our standards or we wouldn’t buy from them,” recalls Peluso. “That’s the only thing that’s going to force the issue. If other people take that stand, it might bring this thing to a head.”

Branded for Life
The main problem many end users have with the current C and ISO codes is that they seem to promote inconsistencies from one manufacturer to another and, hence, make switching from one brand of a given carbide grade to another brand of the same grade a tricky business. “Users are having a difficult time getting multiple sources to provide them with a given type of a product and have equal performance,” notes Hanita’s Steve Abrams.

That makes it hard to judge whether a switch of brands will actually lead to better, or poorer, productivity. Say you buy a new brand of carbide tool and it works better in its first application. That may happen because it’s a better carbide, or it may happen because it’s more suited for that particular operation. If the latter is true, the new tool may perform more poorly than the old tool once you change parameters. Or you may be working the tool too close to its parameter limits, where a small change can cause breakage, whereas the other tool may have a large safety factor where a small change won’t cause a problem at all. “Unless you know exactly what you’re working with, which means either you do a lot of tests or you’ve got to have some kind of standard, then you’re scuppered,” Brookes insists. “People get hooked into using the products of one manufacturer; it is very difficult to carry out the sort of tests that you need in order to change safely to another supplier.”

This is the situation in which Lynn Engelhuber finds his powertrain department. He says that lack of consistency between different brands of the same grade has often caused GM to stick with one toolmaker to avoid going through a lot of testing to try different brands. “We have systems in place that discourage us from changing tool brands in the middle of a model, so that we don’t introduce variants into the manufacture of a product that could affect the quality. There’s a regular procedure of how we have to qualify a new cutting tool on a surface finish. It’s becoming more difficult to change grades or go to different tools.” This has created a dilemma. “If the engineers had their way, we probably would never change brands. But purchasing would like to see us become more cost-competitive, so they’ve been encouraging us to look at different brands to get better prices.”

Grade Gripes
User complaints to their carbide-tool suppliers often involve inconsistent tool life from batch to batch. A producer sends one batch of tools that works great, but the follow-up batch, for no apparent reason, performs dismally. Sometimes, the problem may be a simple case of the producer shipping the wrong grade of tool. “We’ve gotten carbide sent in here with the right geometries but the wrong grade,” says John Deere’s Ed Hermsen. “Basically, they put the wrong inserts in the right box. We have had tool-life problems where all of a sudden we start a new batch of inserts that have horrendous life, we send them back, and the supplier tells us they screwed up the order.”

At GM, says Lynn Engelhuber, “The only type of inconsistency we can find is gross inconsistency. We have most of our tooling set to be changed after a certain number of pieces. But we don’t go for the ultimate achievable tool life. We leave in probably a 10% to 20% ‘slop insurance’ factor, because we’d rather lose 10% to 20% of the tool life than generate scrap or compromise quality. So the tool-change levels are set with some insurance factor built in. Unless the tool is grossly inaccurate, we probably won’t detect it. We’re not running the things in a laboratory, keeping track of how long they last. We could probably have some inconsistency but not pick it up.”

Inconsistent tool life forces users to play it safe by running tools at conservative, and less than optimal, speeds and feeds. To achieve optimal productivity, tool consistency is much more important than a tool’s peak-performance capability. For example, if Brand A carbide tool can machine an average of 100 pieces, and Brand B averages 10 pieces, you might presume Brand A is 10 times more efficient than Brand B. But if Brand B consistently machines a minimum of nine and a maximum of 11 parts, while Brand A ranges from one to 200 parts, then Brand B is actually nine times better. Because, to be safe, you’ll have to change Brand A tools after every piece, whereas with Brand B you can safely run nine pieces before changing the tool.

All major carbide producers will investigate customer complaints about inconsistent tool performance. Typically, they’ll check returned tools for conformance to manufacturing specifications such as dimensions, edge preparation, metallurgical properties, and coating thickness and integrity. Kennametal’s Bernard North notes that this kind of testing can be a very useful source of information for long-term research and development.

Users Take Action
Some larger users have tried various strategies to address the perceived problem of carbide inconsistency from batch to batch. One of the more intriguing strategies is the effort by some end users to push the quality issue back on the carbide-tool manufacturers.

Each year, Boeing uses millions of indexable carbide and solid-carbide tools in the high-speed machining of a variety of materials. “In the past, we focused on tool life as being the chief measure of success,” recalls Boeing’s Fred Heimann. “But we’ve found that the cost of the cutter accounts for 8% to 10% of the cost of the whole machining process. Machine time makes up a much larger percentage.” Today, Boeing stresses consistency and reliability of carbide tools over tool life to lower machining time.

In an effort to improve the consistency of incoming carbide tools, Boeing has launched a program that puts the burden of quality testing back on the tool suppliers. “We have started to buy our carbide tools solely from manufacturers that actually have labs where they perform acceptance testing on incoming carbide-substrate raw materials,” says Fred Heimann. “We’re leaving it up to them to test the quality of the carbide and provide us with certification of the carbide quality.” Boeing currently does no in-house testing of incoming tools.

In its initial quality tests in 1980, Boeing tested all the brands of carbide tools it used. “After making sure our sources met our specifications, we ran comparative tests of various manufacturers that we were dealing with, and from those tests we picked the ones that removed the largest amount of material before needing reconditioning,” says Joe Peluso. “The main thing is, we put the responsibility for product consistency back on the manufacturers, which is where it belongs.”

GM’s powertrain division is in the process of implementing a tier-management program. First-tier cutting tool suppliers will be responsible for the quantities and quality of the tools and for testing to qualify the tools. The system mirrors that of Saturn Corp., Spring Hill, TN, in which Kennametal manages Saturn’s tooling. Kennametal orders the tools from various producers, handles inventory, and supervises regrinding.

John Deere’s engine division has its carbide-tool suppliers test for porosity, density, and composition of the material. Deere’s Dubuque site no longer

inspects incoming tools. “We had to reduce overhead rates to stay competitive,” Ed Hermsen explains. “We have come to rely on our tooling suppliers to provide the correct applications of the cutting tool. They provide the testing and feed and speed directions, and they have floor observers on site during the testing. For them, new or continued business is at stake. For us, cost reductions, improved productivity, and greater reliability are the benefits.”

Hanita entered the carbide-tool market only four years ago. But before making and selling carbide tools, the company had to educate itself about the often confusing world of carbide. “It took us two years just to evaluate the various sources to determine who could supply us with what we wanted,” recalls Steve Abrams. “That meant visits to the plants and in-depth discussions with their engineering departments and R&D departments about quality control, capacity, and price. We got to know the companies in-depth.”

Compared to their European counterparts, most U.S. end users demand little in the way of documentation of processes from their tool suppliers. Rather, U.S. shops tend to rely more on ISO 9000 certification as a reassurance that their suppliers are pursuing quality.

Those that do request documentation tend to be medium-size customers, according to Carboloy’s Debbie Svennevik. “The small companies typically rely on the judgment of their most experienced personnel, while the large ones place major emphasis on certification that recognized quality systems are in place. It’s primarily the medium-size companies that want us to send the numbers, because they are concerned with supplier quality but often don’t have the manpower to come out and check our process directly.”

Many larger end users would still prefer to test incoming carbide tools themselves. “I do regular seminars for companies that want to do that—usually very big companies,” says Kenneth Brookes. “These are not expensive tests. If you have a lab, you probably have a Vickers or Rockwell hardness tester. I teach people to do metallography and examine the microstructure and density of the carbide. The problem is, acceptance testing is generally done against a specification, so testing carbide with no specification is very difficult. You have to make up your own standard.”

Personal Standards
Some of these large companies have done just that. Boeing, for example, requires certification that the substrate material of the tools it buys meets Boeing’s criteria and that the geometry generated matches the specifications Boeing has established in conjunction with the carbide-tool manufacturer. “We’re starting to use more and more carbide in high-speed machining,” notes Fred Heimann. “Since there is no standard for carbide, we’ve worked with manufacturers to establish geometries and material specs.”

“We’ve told anyone that wants to sell us carbide tools to bid on quality raw material,” adds Joe Peluso. “No junk, no recycled material—we want the real thing.”

Determining what compositions to specify for particular operations has proven especially challenging for Boeing, given the carbide-tool producers’ propensity to each give the same carbide a different designation while sometimes giving widely different carbides equivalent designations.

“We pulled as much data as we could from the industry to establish what we wanted,” says Heimann. Joe Peluso adds, “About the time I left Boeing, we started putting together some basic ground rules—our interpretation of a given grade. Some people did a real push back on us, saying this would raise the price of the tool. We replied that we expected a tool with good wear and fracture resistance, and we didn’t think that was an unreasonable request. If a manufacturer isn’t checking its grade before it makes that tool, it’s not giving us quality to start with. If you want to put a quality product on your shelf, you have to find out if there are any discrepancies in your product. If you ignore the raw materials, you may be ignoring the heart of the problem.”

Growing in popularity is the National Aerospace Standard (NAS) created in the late 1970s, which has narrow geometry and compositional requirements targeted to very specific workpiece materials. Today some end users employ NAS as a starting point and then add any further specifications they wish. More and more users outside the aerospace industry are becoming aware of NAS. And because most carbide-tool producers sell tools to aerospace companies, they probably have NAS-certified tools in stock.

Other industries have worked to create in-house standards to ensure the consistent performance of tools in given operations. Sandvik’s Dave Watson says Caterpillar Inc., Peoria, IL, has had a profound effect on cutting tool suppliers’ quality systems.

Caterpillar introduced its quality standard in the mid-1980s. To be certified as a Caterpillar supplier, a tool producer had to have specific control procedures for inspection frequency, SPC, data acquisition, and data documentation.

“It was really good to have everyone examine their processes,” Watson remarks. “And then Ford came in with its Q101 and Q-1 programs, which were very strong motivating forces and good systems for developing quality. Eventually, Q-1 took the lead.”

More recently, the Big Three automakers have jointly established the QS-9000 standard. “But in the QS-9000 quality standard, there are about two lines that refer to cutting tools,” notes GM’s Lynn Engelhuber. “It basically says you have to have a system in place to monitor your tooling and be sure it is refurbished properly, and that’s about all it says. It doesn’t say anything about tool quality.”

The new Tooling and Equipment (TE) supplement to QS-9000 comes a bit closer to addressing carbide-tool quality. It is a process-focused standard for tool producers selling to tooling and equipment suppliers, that is, end users that work mainly with one- or two-part runs. The TE supplement interprets the QS-9000 standard for tooling and equipment people. It stipulates that conforming manufacturers have specific plans for controlling reliability and maintainability of their carbide tools. And certain information, if requested by the customer, must be provided. Mary Pathuis, one of the main architects of the TE supplement and quality-assurance manager of Riviera Tool in Grand Rapids, MI, reports that so far cooperation from carbide-tool producers has been quite good, though currently a shortage of registrars has severely slowed down the certification process.

“If required by your customer, you will be expected to produce information on carbide composition,” says Pathuis. “During the contract-review stage the supplier should obtain a purchase order. The supplier also is expected to understand and document the requirements of the tooling prior to quoting and supplying the product.”

These efforts signify a dissatisfaction with the current C and ISO systems. Classifying carbide grades according to the materials they should cut is an inexact science, potentially subject to temptations to oversimplify or to fill application holes in product lines with less-than-optimal grades. At a time when end users desperately need accuracy and consistency from their cutting tools, such subjectivity may not suffice. An informative, descriptive standard based on objective, testable characteristics—while difficult perhaps to assemble—might better serve their needs.

Editor’s Note: Most of the historical background information for this article was gleaned from Kenneth Brookes’ World Directory and Handbook of Hardmetals and Hard Materials, Sixth Edition, available from International Carbide Data, 33 Oakhurst Ave., East Barnet, Hertfordshire EN4 8DN, United Kingdom. (Telephone: 44-181-368-4997.) The book contains exhaustive lists of carbide compositions and properties from hundreds of manufacturers.