Turning Inserts Face New Challenges

Originally marketed for their proficiency in heavy metal removal applications while delivering longer tool life and multi-point efficiency, turning inserts have grown more sophisticated in response to advances in materials, machines, methods, and even social factors.

Advances in the materials that need cutting are a crucial factor in the development of turning inserts. A new generation of materials, including heat-resistant alloys and specially developed customized materials, has resulted in the strategic development by toolmakers of substrates and coatings for both “off-the-shelf” inserts and “special,” or customized, inserts. The combination of higher speeds and more exotic materials, such as those with high vanadium content, pose an ongoing challenge for toolmakers as customers seek even further efficiencies, according to Travis Coomer, national key account manager at GWS Tool Group,Tavares, Fla.

“You need grades and coatings that are able to withstand high temperatures while cutting. Also, for a lot of materials, like Inconel or titanium, you need sharp geometries. But sharp geometries and cutting edge preparations are highly affected by high temperatures, so [the insert] needs a sharp/positive geometry and a coating that provides heat resistance to get enough tool life,” said Lothar Unglaub, director marketing portfolio management at Kennametal Inc., Latrobe, Pa.

Edwin Tonne, training and technical specialist at Horn USA Inc., Franklin, Tenn., commented, “The new materials are developed with favorable properties for specific applications and aren’t necessarily designed with cutting tools in mind. This is especially true in areas such as medical devices and implants and results in a need for machinability testing. Inserts developed for these applications require highly homogeneous, finer grade carbides to ensure consistent quality and longer life, as well as coatings deposited through sputtering that result in improved density and better adhesion to the substrate.”

Martin Dillaman, manager, applications engineering at Greenleaf Corp., Saegertown, Pa., noted the problems that occur with proprietary materials. “We have to discover how materials interact with the substrate and coating. Obviously, the temperature can degrade the insert if it is too high,” he said. “The solution is to gain as much information on the material as possible. This is easier with common materials, but proprietary stock supplied by the customer can be extremely difficult in that they often refuse to fully release information about the chemistry and, as a result, we have to depend on trial and error rather than simulation.”

The problem of chip control in newer materials is referenced by John Winter, turning specialist at Sandvik Coromant, Fair Lawn, N.J. “At our Aerospace Tech Center, we are continually doing research on new materials. Chip control is a major problem in low-carbon steels in both aerospace and automotive applications. In fact, we refer to it as ‘the Holy Grail’ in automotive machining. To answer this, we are developing substrates created from powder mixes with high heat resistance and, for steel and stainless applications, we are involving Inveio Technology in crystal alignment in coatings.”

Randy Hudgins, national product manager–turning and threading at Iscar USA, Arlington, Texas, likewise noted the value of manipulating the crystal structure. “New grades that reduce friction and heat for a longer life, including CVD coated inserts, have been instrumental in improving the delamination we encounter in certain steels. This has eased the problems of hard-to-break chips and tool life.”

Difficulty in machining materials developed for specific purposes is cited by Jens Bald, product line manager at Seco Tools, Troy, Mich., “These materials are developed for highly specific uses, often not considering their machinability or ease of production. We see the machine shops struggle to find suitable methods and tools to machine these materials, and we support them with our expertise to find a solution. If so needed, the inserts—both substrate and coating—may be tailored to that specific, new material.”

The sequencing of production operations can also play a major part in turning hard alloys. Jim White, national sales manager, Carmex USA, Richfield, Wis., stated, “Machining after heat treating is a huge time saver, but doing it economically is not so easy. Any interruptions, such as grooves and cross-holes, usually cause breakage, so finding the right balance between substrate hardness and toughness makes a big difference. The latest coatings can handle 25 percent more heat than traditional coatings like AlTiN. Since heat-resistant and hardened materials such as nickel and titanium-based alloys are more difficult to machine, higher heat ranges deliver better tool life.”

The importance of “thinking outside the box” and knowing the customer’s capabilities are extremely important, according to Mike Trimble, product manager at Vargus USA, Janesville, Wis. “We’ve encountered situations where the stock the customer was using had a high abrasive content that resulted in having to run at lower surface footage. Our applications engineer is sometimes able to suggest an alternative material that performs as well in the application and results in better performance and less cycle time. It’s also critical to know the capabilities of the customer’s machines to ensure that the insert will perform properly. Further, the toolholder must be taken into account, especially in difficult chip control situations.”

As both machine speeds and the prevalence of automated systems have increased, chip control has become a primary consideration. “The customer needs process security, and a large part of that can involve chip control, especially where multiple machines are involved,” said Winter of Sandvik Coromant.

Iscar’s Hudgins added, “High production operations are especially concerned with chip control. For instance, the aerospace industry is under tremendous pressure due to the number of aircraft that require replacement now. Their use of new, high-temperature materials demands efficient chip control at the tool, as well as in handling throughout the system.”

Dillaman from Greenleaf referenced the influence of better machine capabilities. “Just as materials have evolved, machines today are much more advanced and offer a greater degree of control.” Trimble of Vargus USA agreed. “Today’s equipment is much faster, and customers can maximize tool performance while cutting cycle times.”

When it comes to features and properties desired by customers, longer tool life is always cited, although it becomes a greater priority in more difficult economic times. “Last year, the emphasis was on productivity,” said Dillaman. “This year, for economic reasons tool life seems to be the lead priority.”

Hudgins observed that the customer definition of tool life is highly related to dependability. “Price is one thing. Cost is another. In order to deliver greater value to the customers, we’re heavily involved in insert wear training to prevent premature replacement.”

While tool life is a given, Kennametal’s Unglaub noted the value of “highest possible indexing accuracy and more precise finishing geometries. Obviously, the longer tool life must be characterized by consistent and repeatable performance.”

In general, longer life and the ability to achieve faster cycle times are key factors, according to White of Carmex. “Both contribute to lowering cost by increasing machine utilization or efficiency. If your shop is 50 percent efficient, that would be an extremely impressive number. Most are somewhere around 25 percent.”

Predictability and performance are cited by Abhay Chaubal, turning, threading and grooving product manager at Seco Tools. “Depending on what the customer is manufacturing, tool life can vary. The important considerations are predictable processes and consistency of tool life,” he said.

It’s important to look at what the customer is doing, not just what tool they are using, according to Trimble. “In an automated system, when one machine goes down, you lose the whole line, so in some cases, chip breaking is a primary consideration. In others, it might be the consistency of finish.”

Tonne of Horn USA added, “Features desired by the customer vary by market. For instance, we deal with high stock removal in aerospace. In medical applications, the chief requirements are precision and finish.”

As near-net shape forgings and castings have become more common, better finish quality is desired, observed Winter. “Likewise, the variety of materials used in inserts is expanding,” he said. Whiskered ceramics are becoming more common in roughing operations in the aerospace industry.”

Coomer of GWS noted that, in high finishing applications, more toolmakers are using ground surfaces as opposed to molded. “It’s the combination of the material and the geometry that makes for a successful turning insert.”

As parts have become more complex, and multi-function machines (such as turn/mill) increase in number, toolmakers’ responses have included both special customized inserts and multi-function tools. “We see higher demand for custom solution combination tools with multiple insert pockets, different diameters, different chamfers, and different contours that can be generated with just one cut per tool,” said Unglaub. “We also see an increase in demand for inserts with complex shapes and profiles. As for multiple applications, there are unique cases, but we do not yet see a general trend.”

Seco Tool’s Bald sees an increase in custom tooling, especially at the highest level of optimization and noted that many former specials are now “off-the-shelf” items. Chaubal of Seco commented, “Tools designed for multiple applications include turning and boring tools, as well as our MDT (multi-directional turning) inserts for grooving and parting off. In many cases, specialty tooling involves the development of combination tools that marry several tools into one, e.g. tools for both ID and OD machining. This is especially true in mass production as it relates to any situation where the customer doesn’t want to move the part to another machine for secondary operations because of a possible loss of time and precision.

“Specials have always been a primary offering with us,” stated Tonne. “More customers are open to specials to eliminate offsets and reduce cycle time. They are also used to create complex forms with minimal programming. For instance, the Horn Super Mini HP can turn, face, drill and bore, thereby conserving tool stations and change times. Also, multiple application inserts deliver more features at one shot.”

Hudgins emphasized the importance of the toolholder in both specialty and multi-function applications. “Toolholders not only determine length and reach but can offer multiple pockets on the same tool.” Dillaman added, “A specially designed [toolholder], though it may have higher expense, can be key in both specialty applications and finding ways to double the uses for inserts. With the right holder, we can sometimes use standard inserts that result in much less cost over time.”

White cited the need for caution in multiple-application tooling. “You can end up sacrificing efficiency for convenience,” he said. “Multi-tasking tools do several operations but often do none of them well. For example, a particular tool can have the capability to drill, chamfer, and thread mill. While it only uses one tool station instead of three, all of the processes take more time than if three separate tools were used.”

Trimble presented a particularly unique reason for incorporating special tooling. “In the oil and gas industry, certain customers demand special tooling to make parts that are unique and cannot mate with competitive parts that use Acme threads,” he said. “I think you would call this the ‘proprietary approach’ to customized inserts.”

Turning insert development in the near-term future will continue to center on “newer coatings and substrates for speed and tool life,” said Dillaman. Unglaub added that “The balance between toughness and wear resistance will remain one of the biggest challenges for coatings, as well as for substrates and for insert edge preparations.”

Coomer sees the ongoing need for optimization of the combined substrate and coating, while White observed that “recently, I’ve seen more innovation in grooving for lathe work than in turning. The latest innovations usually require proprietary holders.”

According to Winter, the newest ideas involve both ISO pockets and proprietary pockets that are cutter specific. “In the future, processes will be more refined and will affect both the holder and the insert.” Trimble foresees “new ways of getting high-pressure coolant to the cutting edge, and there will be growth in the press-to-size market.”

Hudgins agreed, noting that “1,000 psi coolant is now the standard. The growing use of 3D printing for many components will result in the development of more inserts for finishing and semi-finishing operations in both rotational and prismatic parts. Inserts aimed at niche markets and ancillary equipment for automated systems will also increase.”

Chaubal anticipated the continuing requirement to “deliver more complete solutions to customers, including educational programs, new materials, finishing tooling for near-net shape and additive manufacturing, and a greater emphasis on sustainability and recycling throughout the turning and machining process.”

Turning insert manufacturers have also been called on to assist in answering some of the social challenges currently impacting the manufacturing industry. Tonne sees manpower as one of the primary factors impacting change. “Frankly speaking, the workforce is not as skilled as it once was due to the decline in trades education. As a result, insert wear identification and ease of use have become considerations in the design of turning inserts, as well as toolholders.”

Bald concurred. “It has gotten harder to attract talent in the manufacturing area. In response, we’ve developed ‘Seco Technical Education Programs’ for application and machining knowledge as well as digital support on our website and the Seco Assistant app.” Chaubal also noted, “We have to design products that assist the machine operator, who may well be less experienced, in finding the right tool.”

Other “social” considerations cited by Bald include increased use of recycled material. “At present, our products include a good amount of recycled carbide. The trend toward recycling and sustainability is growing throughout industry.”

What is clear is that the turning process—thanks to technological advances in materials, machines, and part complexity, as well as external factors such as operator skills and sustainability—continues to evolve. Toolmakers serving the market will have to balance customer demands for comprehensive and often unique solutions against competitive pressures, the emphasis on lower prices, and the high cost associated with research and development. This will, of necessity, result in the need to partner with key customers, to improve and streamline information flows regarding new developments and, where possible, to establish relationships with colleagues who may actually be competitors in other product lines.

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