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Whether Hogging or Finishing, End Mills Are Up to the Task

Jim Lorincz
By Jim Lorincz Contributing Editor, SME Media

There’s a type, geometry and coating for virtually any application or material

NanoFeed high-feed milling line features a 20o lead angle, high-feed single-blade design that utilizes pressed-in coolant channels to precisely deliver air or coolant to the cutting edge. (Provided by Ingersoll Cutting Tools)

End mills are designed to help shops of all sizes maximize tool life and productivity and reduce downtime whether hogging out large amounts of material or producing fine surface finishes on materials as diverse as hardened steel for mold and die, heat-resistant superalloys for aerospace, titanium and Inconel for medical applications.

Machining operations include milling, holemaking, drilling and reaming, profiling, contouring and multifunction processing with combination tools. The best solutions depend on the careful attention to selection of indexable or solid carbide, geometry, cutting tool material, coatings and edge prep among others. Here’s a selection of the product and echnology choices available from leading end mill tooling manufacturers.

Indexables, Solid Carbide Tools

Ingersoll Cutting Tools, Rockford, Ill., offers a wide range of end mill tooling options, including both solid carbide 90o ball nose, bull nose and hi-feed types as well as indexable end mills in modular and integral shank styles. Ingersoll’s broad offering of end mill products allows its customers to select from many tooling geometries engineered for optimal performance in various cutting conditions and applications.

“Our customers face many day-to-day challenges regarding tooling. They include the need to maximize tool life, maximize productivity and reduce downtime,” said William Fiorenza, product manager, mold and die. “We address these three challenges by working closely with customers, learning about their applications and gaining a thorough understanding about cutting conditions, machining capabilities and equipment limitations. The next step is to provide tooling recommendations that align with the application.”

The EMUGE-FRANKEN TiNox Trochoidal end mill is designed for trochoidal milling via the overlapping movement of circular paths, resulting in 30 percent faster roughing and finishing when compared to standard designs. (Provided by Emuge-Franken USA)

Ingersoll has introduced four new end mill families, three indexable and one solid carbide. They include the recently introduced NanoFeed milling line; the HiPosSFeedV 05 inserts series 90o shoulder mill & high feed mills; the GoldSFeed 04 insert series high feed mills; and the new RhinoRounds solid carbide end mill line. The three indexable insert product lines follow the trend toward offering indexable-style tools in smaller diameters, which range from 0.236" (6 mm) to 1.25" (31.75 mm). This is achieved by using smaller IC size inserts (4, 5, 6 and 8 mm). These smaller inserts allow for higher-density indexable cutter options, Fiorenza explained.

The NanoFeed high-feed milling line is available in eight cutter bodies, four steel and four brazed solid carbide versions that offer extra rigidity. NanoFeed features a 20o lead angle, high feed single-blade design that uses pressed-in coolant channels to precisely deliver air or coolant to the cutting edge.

The NanoFeed 20o cutting edge offers a 3× feed rate multiplier. The insert side walls are back drafted slightly to provide extra side wall chip clearance. The maximum DOC is 0.5 mm for the 8 mm insert and 0.3 mm for the 6 mm. NanoFeed is currently available in hard milling grade IN2504.

“Very common fillet radius sizes used by designers when designing parts are 0.125, 0.250 and 0.375" [3.175, 6.35, 9.5 mm.] Indexable insert style mills with smaller IC sizes such as the NanoFeed 6 mm and 8 mm can be extremely helpful. When milling a fillet radius that is in the same axis as the tool, a size-for-size cutting condition can exist if the cutter radii and part fillet radii are the same.

“For example, a 0.375" [9.5-mm] diameter tool milling a 0.1875" [4.76-mm] fillet radius would be size for size. This does not promote a good or optimal cutting condition,” said Fiorenza. “A better solution would be to mill that 0.1875" fillet radius with a smaller diameter tool, such as an 8-mm diameter tool which has a 4-mm radius. Doing this would allow the tool to better drive the corner radius when milling. The cutting action would be more free with less chatter,” Fiorenza explained.

GWS custom, standard and modified standard cutting tools include end mills that range from general purpose to application-specific or material-specific. (Provided by GWS Tool Group)

Ingersoll’s new line of five-, six- and seven-flute solid-carbide variable pitch RhinoRound end mills are designed for semi-finish, finish and high-efficiency machining applications where more flutes provide greater productivity. These tools excel in higher-hardness materials 28 HRc and above, including steels, stainless steels, cast irons and high-temperature alloys.

The variable pitch design reduces vibration when multiple flutes are engaged in the workpiece and provides a combination of reduced cutting forces and excellent chip evacuation, according to Ingersoll. The RhinoRound RE1 and REB series tools are available with flute length and corner radii options. The five- and six-flute tools are also available as ball nose tools. Each tool features an eccentric grind which performs very well in moderately hard materials, and all are made with a submicron substrate for good toughness and wear resistance. All RhinoRounds are provided in IN2205 grade which is a nano-layered PVD-TiAlCN featuring a unique powder blue color.

Solutions Match Material Challenges

Emuge-Franken USA, with headquarters in West Boylston, Mass., offers end mill applications expertise and solutions, supporting machining difficult materials.

TiNox-Cut End Mills, for example, are designed for high-performance machining of demanding materials such as Inconel/nickel alloys, titanium and stainless steel. The end mills are made from premium ultra-fine micro grain solid carbide with a maximized transverse rupture strength for high-impact applications, producing impressive results compared to conventional end mills, according to Emuge-Franken USA’s Dan Doiron, milling products manager. “Advanced PVD-applied multi-layered coatings withstand excessive heat and provide superb wear resistance for longer tool life. Tool geometry is designed to produce minimal vibration when machining tough materials,” he said.

“We recently worked with a customer to improve tool life and decrease part cycle time when milling 400 stainless steel parts with a hardness of 40 Rc,” said Doiron. “After reviewing their application and current end mills, we recommended TiNox Trochoidal end mills, and were able to cut cycle time in half from two hours to one hour and increase tool life by 5×.” In addition, Doiron reported the new solution saved 88 percent in job costs because even though, for example, the Emuge solution has a higher cost-per-tool, only 16 Emuge-Franken end mills are required as compared with 200 of the original tools.

Emuge-Franken TiNox Trochoidal end mills have a combination of proprietary TiN/ TiALN coating and a chip-breaker edge that reduces stress and vibration when machining difficult materials such as stainless steel and titanium. The chip-breaker edge feature is designed to reduce the length of the chip produced to smaller segments, making chip evacuation easier, specifically in deep-pocket applications. All tools are coolant fed for maximum performance.

Designed for trochoidal milling via the overlapping movement of circular paths, these tools can rough and finish mill over 30 percent faster than standard designs, while increasing tool life significantly, the company said.
Designed for virtually all materials and applications, Emuge-Franken’s TOP-Cut VAR High Performance variable-helix carbide end mills feature geometry and coating that make them equally effective in multiple job shop applications as well as challenging production cutting operations.

According to Emuge-Franken, TOP-Cut VAR end mills feature unique flute and profile geometries optimized for long tool life and superior performance in both roughing and finishing applications. Variable helix angle flutes provide extensive vibration dampening and are precision ground with advanced edge preparation to maximize chip evacuation. A small chamfer feature protects cutting edges to prevent chipping of the face geometry. Bull nose end mills have fully blended corner radii to extend tool life, while providing improved surface finishes.

All TOP-Cut VAR end mills have an advanced ALCR PVD coating for outstanding performance and extended life in higher operating temperatures. A proprietary sub-micro grain carbide provides maximum abrasion resistance and durability.

Doiron said that Emuge customer SB Dezigns, North-East, Md., had encountered long cycle times milling stainless steel shifter parts for the racing industry. Successfully implementing TOP-Cut VAR End Mills together with an Emuge FPC Milling Chuck saved 62 percent in costs. Before this, SB Dezigns was using a couple of different brand end mills and was not optimizing the milling process. Billy Crabtree, owner and CEO of SB Dezigns said, “With the Emuge end mills and holder combination, we are able to save over 30 hours of machining time and more than $5,000 for every 500 shifter parts we manufacture.”

Tools Tailored to Applications, Materials

GWS Tool Group, Tavares, Fla., is a vertically integrated manufacturer of highly engineered custom, standard, and modified standard cutting tools including end mills. End mills range from general purpose to application-specific or material-specific, according to Drew Strauchen, executive vice president. “Often custom tooling solutions result from standard tools that have been tailored and tweaked to the customer’s application. To find the best tooling solution, we drill down into the customer’s application information: what’s the material? The shape of the part? What’s the final objective? Longer tool life? Faster cycle times? What finish is required?”

The answers for GWS’s aerospace customers are usually developed for structural components for commercial and defense aircraft featuring aluminum, titanium and composites, as well as tools for heat-resistant alloys for the hot engine side. Material focus in the automotive industry includes high-silicon aluminum, ductile cast iron and compacted graphite iron (CGI). The materials are fundamental in the auto industries transition to lighter weight materials. The medical sector tooling solutions include stainless steel, titanium and cobalt chrome for implants such as bone screws and knee joints.

GWS offers custom brazed ceramic to carbide end mills for machining heat-resistant superalloys and 5-7FL coated carbide end mills with material-specific geometry and specific edge preps for machining titanium. For non-ferrous applications, Strauchen said that PCD tooling is one of the hottest areas of growth, where brazed PCD inserts and PCD monoblock tools are being utilized for aluminum castings and eight-facet PCD drills for processing aerospace composites for aircraft skins and wing spars.

Ceratizit’s four-flute variable helix end mills with P007 geometry and P556 geometry reduce vibrations, resulting in longer tool life and better finishes. (Provided by Ceratizit)

“There’s also growing demand for products that can do more with one tool,” said Strauchen. “Our HurrimillAT4 four-flute multifunctional end mill is what we call an all-terrain type of tool for drilling and ramping, tool counterboring, high-speed machining and conventional slotting/roughing. Job shops can do more with one tool in the spindle that does several operations and is extremely forgiving. It’s a drill and end mill in one tool with a brand-new FX7 PVD coating that makes it well suited to doing slotting and profiling, ramping, plunging, high-speed milling and roughing and finishing.”

“Our customers are focused on cycle time and throughput. They know that the most costly expense they have is time. We are focused on saving cycle time through faster metal removal rates, reducing cost per part via longer tool life and reducing tool changes by creating custom solutions that combine multiple tools into one—e.g., step drill with countersink does three operations.”

Strauchen said that GWS’s Alumigator ASR5 five-flute coolant-fed super rougher is capable of high-speed roughing and finishing aluminum with high-speed 18,000–20,000 rpm machines. “With a high-speed, high-horsepower CNC we can achieve over 1,000 ipm and over 200 in3 metal removal rate.”

Strauchen said that a lot of GWS standard tools, like those for machining titanium, started out as custom solutions. “A high-feed line of titanium end mills was developed as a custom tool first. We had such a great success with it so that we created a standard tool portfolio,” he said. “We had to work with customers to reprogram toolpaths because that type of tool can be very effective with the right toolpath. The High Feed end mill is designed for Z-level machining in five-axis machining.”

Application Specificity or Versatility?

Iscar USA, Arlington, Texas, provides solid carbide end mills designed to meet its customer’s requirements. For example, customers are concerned with three primary drivers in analyzing the overall cost to produce a part. Machining costs (productivity), tooling costs (cost per edge) and tool change cost (tool life), are prioritized based on the customers goal, according to Matt Clynch, national product specialist—milling. “With the design software and advanced grinding machine and software technology that is available today, we are able to tailor precision end mills for the most complex applications. Miniature facets can be applied to cutting edges for titanium or flutes tailored to ejecting stainless steel chips.”

Iscar’s end mill designs are engineered based upon the environment that the tools are to be used in. “For example, if you are doing job-shop type work, our new FLASHSOLID end mill line offers performance at an economical price point. This new family of end mills are 100 percent made in the USA. There are up to 3,000 possible configurations, including flute count, corner radius, length of cut and overall length that can be used on most common types of materials found in a job shop,” said Clynch.

“For application-specific environments, we offer high-performance Chatter Free end mills for high-production applications or shops that specialize in difficult-to-machine materials like Inconel, titanium or stainless steel. Solid carbide end mills that are designed for stainless steels, heat-resistant super alloys, or hardened materials up to 63 HRc are able to drive the cost per unit down while giving a shop the balance of tool life or productivity needed,” Clynch explained. “In those manufacturing environments, savings of a second and/or minutes can really add up to huge [cost] savings.”

Iscar’s Multi-Master solid carbide end-of-tool offers the best of both worlds, according to Clynch. Multi-Master is a solid carbide threaded head or tip that screws into a shank that can be carbide, steel, or heavy metal. “It doesn’t have the length-of-cut of other solid carbide end mills. Its range is limited to 0.75 to 1.5×D on flute length. We can’t achieve the great depth of cut (2×D and greater) of solid carbide end mills, but it allows us to do fast feed end milling, corner rounding tools, spot drilling, center drilling, slotting, grooving cutters, [or] engravers—all being solid carbide. There are as many as 52,000 different combinations of heads and shanks considering all the shank choices to reduce tool change out time.”

Iscar’s solid carbide end mills are available with a combination of substrates and coatings. For example, “A general-purpose end mill with a sub-micron grain structure offers good wear resistance as well as high toughness and some forgiveness with the tool. On the other hand, an ultra-fine grain structure offers more wear resistance for hardened steels or carbon fiber reinforced plastics.”

Iscar offers four different types of coatings that are standard on its end mills. They include 9 series AlTiN (better without coolant); 3 series TiCN (better with coolant); 6 and 7 series (AlTiCrSiN) for more wear resistance to abrasiveness.

V7PlusA end mills feature four and six flutes with a full range of tool lengths and corner radii for high-performance machining of stainless and titanium. (Provided by YG-1)

Solid Carbide Round Tools

According to Yair Bruhis, YG-1 Tool Co. is one of the world’s largest consumers of high-speed steel (HSS) and one of the top three consumers of cemented carbide raw materials. YG-1, with U.S. headquarters in Vernon Hills, Ill., produces around 3 million to 4 million solid carbide end mills per month in 10 grades of carbide in its manufacturing facilities which are spread out in South Korea, U.S., Mexico, Turkey and Germany.

“Most of the end mills that we manufacture are standard products from catalog, but we also manufacture special tools for specific applications and materials,” said Bruhis. YG-1 uses various types of tooling materials, carbide, ceramic and High Speed (HSS) and powder metal (PM).

“Tooling choices range from special solid-carbide grades for taking lighter cuts on hardened steel for mold and die parts to geometries, coatings, edge prep and surface prep that are more suitable for softer materials like titanium. Everything depends on the customer’s application,” said Bruhis, who develops tools for aerospace, power generation and medical industry as well as automotive. “Most of the round tools that you see in the market today are carbide tools because of the introduction of new machine technology which can run so much faster and is steady. However, YG-1 is one of the very few companies left manufacturing HSS cobalt tools. These are required for older machines and for large diameters, inch and-a-quarter and larger tools,” Bruhis said.

“High-speed machining allows end-users to take very light cuts that can eliminate heat and edge chipping of the tool. As a result, tools last longer and the workpiece doesn’t suffer from heat damage or distortion. Sometimes, you can’t do that because you don’t have the right machine or the right part or the right program. My challenge is to constantly fit the tool to the machine technology,” said Bruhis.

“When you are talking about Tier One companies like Boeing and Airbus or GE Aviation for engines, products need to be certified through a lengthy process of testing. For one tool for a specific engine, it took two years to approve the tool. It involved a lot of testing, at various cutting conditions and tool life. Once the tool is certified for that part, it will not be changed easily. There would have to be some quality issue or failure of the part or some pricing change to justify new testing. For medical certification with the FDA, the same is true. It’s almost impossible to change tooling,” said Bruhis.

Among its recent product offerings, YG-1 has started manufacturing ceramic end mills for Inconel and Waspaloy aerospace engine applications. YG also manufactures a high-performance solid carbide end mill, its V7PlusA end mill with four and six flutes and with a wide choice of flute lengths and corner radii. It is designed for high-performance machining of stainless and titanium. YG-1 has designed a new solid carbide end mill called the TitaNox-Power HPC, with five flutes for titanium alloys, stainless steels and Inconel machining.

The Alu-Power family of aluminum machining end mills includes the Alu-Power HPC for high-speed machining, the Alu-Power two- and three-flute end mills for general machining of aluminum and the Alu-Power HPC chip breaker roughers for roughing aluminum and nonferrous materials.

Carbide Consistency from Powder to Product

Ceratizit USA Inc., Warren, Mich., is a fully integrated manufacturer of carbide tools that controls consistency of its products from the ground up to fully finished tooling, according to Steve Kuhnle, regional sales manager. “We manage the entire production process of cemented carbide and cemented carbide components from powder preparation to forming, sintering, finishing and surface treatment,” said Kuhnle.

Products include solid carbide standard milling cutters and HPC milling cutters for applications in a broad customer base including aerospace, automotive, medical and the firearms industry. “Material-specific tools are designed for difficult-to-machine materials, high-temperature alloys, nickel-based alloys and pH stainless steel, along with a lot of 17-4, 13-8, 15-5,” said Kuhnle.

Ceratizit’s products include rods and preforms for solid carbide tools as well as carbide components for applications such as the medical industry. Products not covered by the standard range are developed by Ceratizit’s carbide experts on an individual basis and in close collaboration with the tool manufacturers.

Kuhnle credits Ceratizit’s new Dragonskin coating process and the way the company preps its end mills with producing an extremely hard and durable coating. “What we do prior to coating and after coating makes the difference. We prep the end mill before coating and after by polishing the end mills to produce better adhesion and durability.”

“Ceratizit’s multi-application grade AlTiN-based coating is applied to tools that are used for difficult-to-machine materials like hardened steels, alloy steel and superalloys. The Dragonskin DPB60S coating technology makes the surface particularly smooth, which improves chip removal and reduces adhesion for cutting hardened steels, alloy steels and superalloys. The Dragonskin DPB72S is designed more for difficult-to-machine stainless and heat-resistant alloys,” said Kuhnle.

He noted that coated end mills are especially effective for aerospace applications where tool life, tool cost and reducing the number of tool changes are the manufacturer’s main challenges. “With our P007 geometry and P556 geometry, our four-flute variable helix end mill reduces vibrations, resulting in longer tool life and better finishes,” he said.

Emphasizing the importance of coatings, Kuhnle said that about 95 percent of the carbide tool cutting edges are coated these days. “The increase in surface hardness boosts the wear resistance of the tool and reduces slide resistance during chip removal. Ultra-smooth surfaces limit the propensity for weld buildup and built-up edge formation, and the insulating effect of the layer increases the elevated-temperature hardness. Significantly longer tool lives are achieved as a result,” Kunhle said.

Ceratizit is a supplier of tools to the demanding firearms industry, where improved geometry and coatings have produced 30 percent increase in feeds and speeds in machining stainless, according to Kuhnle. “For an aerospace application, we recently improved 3D machining of a 416 stainless impeller blade by 25 percent, and reduced costs by 17 percent,” he said.

Ceratizit’s $10 million investment in its Sacramento, Calif., end mill manufacturing plant with 111 CNC machines has made it one of the largest end mill manufacturers in the U.S. “Products made in the plant include solid carbide tools ranging from 0.005" [0.127 mm] ball nose end mills to inch and a quarter solid carbide end mills 8" [203.2 mm] long, as well as specials,” Kuhnle said.

An Alphabet Soup of Coatings for End Mills

Titanium Nitride (TiN) is a general-purpose coating that provides high lubricity and increases chip flow in softer materials. The heat and hardness resistance allows the tool to run at higher speeds of 25 percent to 30 percent in machining speeds vs. uncoated tools.

Titanium Carbonitride (TiCN) is harder and more wear resistant than Titanium Nitride (TiN). It is commonly used on stainless steel, cast iron and aluminum alloys. TiCN can provide the ability to run applications at higher spindle speeds. Use caution on nonferrous materials because of a tendency to gall. It requires an increase of 75–100 percent in machining speeds vs. uncoated tools.

Titanium Aluminum Nitride (TiAlN) has a higher hardness and oxidation temperature versus Titanium Nitride (TiN) and Titanium Carbonitride (TiCN). Ideal for stainless steel, high alloy carbon steels, nickel-based high-temperature alloys and titanium alloys. Again, use caution in nonferrous material because of a tendency to gall. It also requires an increase of 75 to 100 percent in machining speeds vs. uncoated tools.

Aluminum Titanium Nitride (AlTiN) is one of the most abrasive-resistant and hardest coatings. It is commonly used for machining aircraft and aerospace materials, nickel alloy, stainless steel, titanium, cast iron and carbon steel.
Zirconium Nitride (ZrN) is similar to Titanium Nitride (TiN ), but has a higher oxidation temperature and resists sticking and prevents edge build up. It is commonly used on nonferrous materials including aluminum, brass, copper and titanium.

Uncoated tools do not feature supportive treatments on the cutting edge. They are used at reduced speeds for general applications on nonferrous metals.

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