Coatings, materials and geometries create innovative combinations, challenges.
No one can accuse cutting tool manufacturers of not trying every possible combination of coating, substrate, material and geometry in their quest to gain a competitive edge for their customers.
Improvements in indexable cutting tools extend to virtually every cutting process. Until the day when it will be sufficient to establish a baseline for comparative and competitive tooling performance through data analytics (a distinct future possibility of digitization and the IIoT), cutting tool manufacturers will rely on tried-and-true processes.
They will mix and match data about chemical makeup, substrates, geometry and machine capability to advance technology the old-fashioned way—by R&D expertise, trial and error, internal testing and validation of new concepts in the field. Here’s how major cutting tool manufacturers are advancing the technology of indexable cutting tools.
A Big Edge in Indexables
“Indexable tooling exists for almost every type of application: milling, turning and grooving, drilling, slotting, boring, and reaming,” explained Luke Pollock, product manager, Walter USA LLC, Waukesha, Wis. “They all use different styles of inserts designed for the needs of the applications. Typically, indexable tooling is considered larger and therefore stronger, capable of taking higher horsepower cuts and higher material removal rates compared to solid tooling. As a result, indexable tools have become more competitive in applications traditionally dominated by round tools.”
Indexable tools can be used in almost every application. “We are seeing more use in high-speed aluminum machining,” he said. “Advances in insert geometry and grades, as well as balanced tools and rigid holding of the insert, allow indexable tools to be used at higher rpm and sfm. Aluminum machining can take advantage of high rpm and machine tool builders have been developing spindles to run at these speeds. Traditionally, solid tools would have to be used in these applications due to balance and rigidity.”
Positive cutting geometry can maintain acceptable, if not increased, tool life and allows for lower horsepower cuts and less torque on the machines, according to Pollock. However, this can create a weak cutting edge.
“Current insert substrates and pressing technology allow for free-cutting positive geometry that doesn’t easily chip,” he said. “Positive geometry can even be added to inserts with negative basic shape or even tangentially mounted inserts.”
Brazed tooling is generally considered to have tighter tolerances since the assembled tool can be finished (ground and polished). These harder materials in brazed form are usually limited in the cutting geometry that can be used in the tool design. Indexable inserts have the opportunity of geometry pressed into the insert so that different machining applications can be handled simply by using a different insert with different geometry or grade.
Pollock said that there are some machines and applica-tions where the machines can push the capability of the tools in aluminum machining. “But I think the more common point is that modern cutting tools allow machines to do more. Carbide substrates and free-cutting geometry increase the capability of smaller machines to process a wider variety of materials and large parts,” he said.
Focus on Indexable Drilling
In recent years, Iscar Metals Inc., Arlington, Texas, has made performance improvements by adjusting the alloying elements in tungsten carbide substrates, using new combinations of various coating layers and applying post-coating treatments. Iscar has also developed different edge prep geometries for a variety of material group applications.
“These features have contributed to increases in operating parameters and tool life and resulted in innovations in indexable tools for holemaking,” said Craig Ewing, national product specialist-drilling for Iscar.
According to Ewing, Iscar now offers indexable head drills from 0.157 -1.575″ (4.0-40.0 mm) dia. Most of that range is offered in 0.004″ (0.10 mm) increments. Drill bodies are offered in 1.5xD, 3xD, 5xD, 8xD and 12xD drilling depths with some bodies offering chamfer collars for combined operations. In addition, standard tooling designs are also being incorporated into special tool applications to increase productivity in medium to large quantity part runs. The special tool is often more expensive than a standard tool, but because it utilizes standard indexable carbide inserts the consumable costs can be greatly reduced.
Iscar continues to expand the line of drilling tools with new cutting geometries. In the Sumo-Cham line there are different edge preps for steel (P), stainless steel (M), cast iron (K) and non-ferrous (N) materials.
For deep-hole applications (>8xD), Iscar has also added double-margin drilling heads as well as inserts designed with self-centering, chip-splitting and flat-bottom geometries. In the DR-Twist line (four cutting edge inserts), there are geometries for general applications (medium to high feeds), soft materials (low to medium feeds) long-chipping materials (added chipbreakers) and aluminum (ground sharp edge, polished face).
For drilling, along with the SumoCham and DR-Twist lines, Iscar offers the LogIQ-3-Cham, Cham-IQ Drill, Combi-Cham and Modu-Drill, as well as solid-carbide drills. The LogIQ-3-Cham three-flute drill offers higher feed rates due to the extra flute and creates more accurate holes in terms of diameter tolerance and roundness. The Modu-Drill series [1.299-1.575" (33-40 mm)] has interchangeable heads for different sizes and styles (Cham-IQ Drill, Combi-Cham and DR-DH).
For deep-hole applications, Iscar offers a line of BTA drills in single-tube and double-tube variations; indexable gun-drills including the Sumo-Gun and Tri-Deep; and standard gundrills. Indexable reaming tools include the Bayo-T-Ream, Index-H-Ream, and Solid-H-Ream.
“New indexable cutting tools often require faster spindle speeds, increased feed rates and multi-axis capabilities that today’s modern CNC machines are capable of to maximize their performance,” said Ewing. “For example, a 0.157″ [4[4-mm]umoCham drill can run above 11,000 rpm and up to 40 ipm [1[1 m/min]n mild steel. Even at the low end, you need more than 6,000 rpm for this tool. Some machines from 10-15 years ago would not be able to properly run this tool.
“Today’s mill-turn machine offerings make it easy to combine many operations into one setup that often had to be done in multiple setups in the past. Iscar offers indexable tooling solutions that take advantage of these machine capabilities, such as multi-function tools for turning, facing and threading operations.”
Ceramic, Carbide Performance
Greenleaf Corp., Saegertown, Pa., is continually working to develop improvements in geometries to match the capabilities of its ceramic and carbide grades. The following is based on a written assessment of product and technology advances provided by the Greenleaf Applications Engineering Team.
“By pairing our patented Excelerator ball nose insert geometry with our WG-600 and XSYTIN-1 grades, we provide customers with the ability to mill hardened and difficult-to-machine materials with a full-radius ceramic indexable tool. Our Excelerator ball nose inserts with patented geometry offer better performance, longer tool life and superior cutting action across a wide variety of materials.”
Greenleaf’s latest advance and newest offering is the phase-toughened XSYTIN-1 ceramic which has “unprecedented edge strength, transverse rupture strength (the ability to support large forces, i.e. heavy chip flow), thermal shock resistance and toughness. XSYTIN-1 is also the most versatile ceramic in Greenleaf’s portfolio, successfully machining soft mild steel, weld-overlaid cobalt-based alloys and anything in between,” according to the Greenleaf team.
Whisker-reinforced ceramics have sufficient hardness (and more than sufficient toughness) to machine most of the materials where carbide tools lack hardness and CBN lacks toughness. In addition, the tooling costs associated with indexable ceramics are significantly lower per cutting edge than they are for CBN.
Another material that has not been an application area for ceramic indexable tooling is stainless steel. Duplex, 300 series and precipitation hardening steels are now being machined effectively with Greenleaf’s whisker-reinforced ceramics, according to the company.
WG-600, a coated whisker-reinforced ceramic, in particular is showing “outstanding performance in turning. Finally, applications where even large-grain carbide lacks toughness (heavy interruption, impurities, forging scale) can now be addressed with XSYTIN-1 where other ceramic and carbide tools break.”
There is still room to maximize ceramic indexable tooling. “Unless we are running on state-of-the-art, purpose-built, latest generation machines, we are limited by the rigidity, dynamics or power when applying ceramic indexable tools. In an ideal environment we are able to turn Inconel 718 at 1,476 sfm (450 m/min) with WG-300, or at 820 sfm (250 m/min) with XSYTIN-1, but with a very heavy chip,” according to the team.
High speeds or high cutting forces amplify even the smallest instabilities in a machine, leading to deflection and, since the process is inherently cyclic, vibration. No matter how tough a ceramic is, vibration leads to irregular mechanical loads that bring about irregular wear that then translates into poor tool life.
“To be fair, there are other uncertainties that could be contributing to instability—lack of rigidity and vibration dampening in the fixture, for example,” according to the team. “Comparatively few machines are also equipped with high-pressure coolant, which is extremely beneficial in the rough- and medium-turning of heat-resistant superalloys in that it greatly improves chip management (and to some extent also improves the dissipation of heat from the tool).”
In Search of Solutions
Improvement in indexable tooling requires a holistic approach, according to John Winter, product management-East U.S. for toolmaker Sandvik Coromant, Fair Lawn, N.J. “We are pushing every aspect of the process to produce the best cutting tool solution possible, from coating technology to the macro and micro geometries that produce a stronger edge line to the post-treatment processes that give the coatings a harder, smoother surface.”
Indexable cutting tools are being used for innovative applications. “The biggest advancement for indexable tooling is in the application of those tools,” said Winter. “We are getting away from the ISO standard and pushing the limits of both tools and machines with creative designs. PrimeTurning is a perfect example of this. Using multi-directional turning, we see big gains in productivity and tool life. It used to be that ISO milling was the popular choice but now you would be hard pressed to find ISO milling in shops. By looking outside of ISO turning, we can push the tools, machines and the limits of the carbide inserts.”
When it comes to performance of indexable cutting tools compared with brazed PCD, CBN and carbide tip tooling, “it’s a question of cost and application,” Winter said. “Anytime you can use an indexable tool, the cost will be lower. The performance is in the cutting material (PCD, CBN, or carbide) and it’s a matter of if the tool can fit into the application.”
One example is boring a large bore where an indexable boring bar will fit vs. using a small bore where only a brazed tipped bar can fit. The same is true of milling and drilling. “Here you can find advancements with PCD-veined tools versus brazed tools where the PCD is pressed into the tool not brazed,” he said. “This allows us to shape the PCD to the mill or drill tip, giving these tools better performance.”
Winter said that the latest developments for indexable milling, turning and drilling tools are more application-specific tools designed to perform a set operation at the highest level of performance. The processes will be optimized to maximize the machine tool, workholding and the tooling for a set application or component.
“Time is money. By pushing the machines and the machines pushing the tooling, we can meet the needs of our customers and help save time and be more profitable,” Winter explained.
Maximizing indexable cutting tool performance depends on whether or not operators are pushing their machines to their fullest potential for both tooling and process. “We need to educate our customers on best practices to be more aware of their machine utilization,” he said. “Many shop owners or plant managers can only give you an educated guess of their actual machine utilization and that utilization is sometimes much lower than they think. And on-lights, stopwatches and clipboards are being replaced by machines and tooling with sensors that can give thousands of data points.”
Winter pointed to Sandvik Coromant’s CoroPlus digital machining system as an example. “With the use of CoroPlus, you can use machine analytics to see exactly where you can make improvements to maximize your production. CoroPlus is data-driven process control that will push the tools and machines to the highest level of productivity possible with modern tooling,” he said.
Advanced Coatings, Applications
Seco Tools LLC, Troy, Mich., has developed advanced coatings such as a Niobium PVD thin coating for machining titanium and plans further advances in its Duratomic aluminum oxide-based CVD coating for general types of steel and cast-iron machining.
“We’re seeing a split in the market, a split where the indexables are being used for roughing and solid-carbide end mills do the finishing, especially as production components are becoming more near-net shape,” said Todd Miller, product marketing manager. “There is an equal need for indexables today as there is for solid tools.”
Cutting tool improvements range from some actual grades that are being refined with additives in the substrate for better wet or dry machining to product upgrades. Improvements to Seco’s Perfomax indexable insert drill, for example, include an improved, highly polished body with wave pattern technology for chip evacuation, increased hardness for wear resistance and elimination of coating altogether.
“In turning, everybody has the same ISO standard toolholders so it’s technology like our Steadyline anti-vibration holders, Jet Stream tooling holders and second generation Duratomic coating that makes a big difference,” said Miller. “In milling, there have been many technological advancements as well as process improvements. Today, processes like dynamic milling require high-tech tools that take a full axial DOC and a light radial DOC at an extremely high feed rate.”
Within its milling family of products, Seco Tools is launching a double-sided face mill called the Double Quattromill 14, building on the success of its Double Quattromill 22 face mill for roughing and semi-finishing introduced at IMTS 2018 for heavy DOC machining.
“We are integrating the same positive cutting action and effective cutting rake angles of our single-sided insert cutters into our double-sided insert cutters. Incorporating the geometry of the single-side, four-edge square type insert into double-sided inserts allows you to get free cutting action and economy,” he said.