Horn offers tools capable of turning and drilling - aluminium milling insert
Part of the reason CBN is run dry is because, while it can take the heat, it does not operate as well with temperature fluctuations. “When a CBN insert actually interfaces with the material, heat is created at the tip of the tool,” Economan said. “But because the CBN doesn’t like shifts in temperatures, it is difficult to adequately cool it to where you can maintain a more constant temperature.The hard CBN is very brittle and could crack due to temperature changes.”
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Iscar’s Schmitz also suggests running the cutting tool “upside down.” He explained: “Mounting a tool in a machine so the insert is facing upward during the cut is the machine tool builder’s preferred way to mount tools because the rotation of the part exerts downward pressure on the machine ways or rails, stabilizing the machine tool. But as the insert goes across that material, a chip forms and may remain on top of the insert and the workpiece. If I take that tool and flip it upside down so I no longer see the insert, the chips are flowing away from the working zone and I’m using gravity to my advantage.”
“Each of these devices can be ordered with special options that might pertain to the application being performed. Special ID tolerances, extended nose lengths, extended land surface, over gripping geometry, or special ID shapes are all things that can be modified on a guide bushing or pickoff collet,” says Scott Laprade, marketing manager, Genevieve Swiss Industries, Inc.
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When cutting softer steel, say 45 to 50 HRC, with carbide, ceramic or PCBN, chips should be as short as possible. This effectively removes heat from the material during the cutting process because the heat stays with the chip.
Chip control is not an issue for 58-HRC and harder applications. Dry grooving is the norm, and the chips are more like dust or very small particles, which can be removed with a manual air blast. “If a chip touches anything, it usually just falls apart,” said Sumitomo’s Maton, adding that chips won’t mar parts upon contact. “If you grab a pile of chips, they would just crumble in your hand.”
Modular holders also provide many options. “Iscar’s Modular-Grip system mounts various products. You can use one shank with seven different blades to run seven product lines, or any number of blades for the same product line but with different widths,” Schmitz said.
Machining operation in which material is removed from the workpiece by a powered abrasive wheel, stone, belt, paste, sheet, compound, slurry, etc. Takes various forms: surface grinding (creates flat and/or squared surfaces); cylindrical grinding (for external cylindrical and tapered shapes, fillets, undercuts, etc.); centerless grinding; chamfering; thread and form grinding; tool and cutter grinding; offhand grinding; lapping and polishing (grinding with extremely fine grits to create ultrasmooth surfaces); honing; and disc grinding.
“Modular holders are going to be used where you see a lot of catastrophic failure,” Schmitz said. “Instead of replacing the entire holder, you just replace a less-expensive component.”
“Most Swiss machines just use flood coolant [and have] a little stick out there shooting the oil where you’re cutting. That may or may not be an accurate way of getting [coolant] there. [The reCool system] brings the coolant in through the nut, and now you can go through your cutting tool, something that’s always been hard to do with a Swiss machine,” says David McHenry, engineering and technical manager at Rego-Fix Tool.
Hardness is a measure of the resistance of a material to surface indentation or abrasion. There is no absolute scale for hardness. In order to express hardness quantitatively, each type of test has its own scale, which defines hardness. Indentation hardness obtained through static methods is measured by Brinell, Rockwell, Vickers and Knoop tests. Hardness without indentation is measured by a dynamic method, known as the Scleroscope test.
Rigidity is important for setups and workholders. Because grooving involves significant edge contact, it produces significant tool pressure. When fixturing hardened workpieces, wide clamps can distribute the clamping surface. “You definitely need to support the area being machined,” said Paul Ratzki, marketing manager for Sumitomo Electric Carbide Inc., Mt. Prospect, Ill. “With hard material, you have much greater vibration and tool pressure, which can cause the part to fly out of the machine, or chip or even break the CBN insert.”
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Over the past decade, finish grooving hardened steel parts using polycrystalline cubic boron nitride inserts has increasingly replaced grinding. “Typically, grinding is a more stable process that provides more accurate tolerances than grooving,” said Tyler Economan, proposal engineering manager for INDEX Corp., Noblesville, Ind. “However, people are trying to do more complete machining on workpieces if the turning machine is capable of completing the necessary processes.”
“Manufacturers have really paid attention to the growing market and needs of the Swiss turn industry, so there really is a lot available [that meets] the needs of the Swiss-type turn shops,” he continues. “Considerations in tooling must also be made in relation to the geometry of the part and a possible non-standard program format to create certain part features. Some Swiss machines are limited on stick tool stations. There are many new tools out there that combine several things like face, turn, groove for the O.D. or drill, bore, and thread for the I.D. By using these combinations we can free up tool stations allowing us to machine more complex or tooling intensive parts with the limited stations.”
“Typically PVD coatings or uncoated tools are used for Swiss-type turning operations,” says Ludeking. “These provide the sharpest cutting edges, thereby reducing forces on the small workpieces. Also, these tools have higher edge toughness that helps them withstand the high forces generated when cutting at low speeds often encountered in small diameter components. Because CVD coatings require somewhat larger edge-rounding (hones), they tend to generate higher cutting forces that are detrimental to small components. On the positive side, new CVD coating technology is enabling smaller hones, making them good choices for higher speed operations or very abrasive alloys,” he adds.
Cutting tool material consisting of polycrystalline cubic boron nitride with a metallic or ceramic binder. PCBN is available either as a tip brazed to a carbide insert carrier or as a solid insert. Primarily used for cutting hardened ferrous alloys.
Iscar Metals offers GITM Groove Turn inserts in two PCBN grades: IB10H for medium- to high-speed continuous machining of hardened steel and B20H for interrupted cutting of hardened steel.
Rego-Fix Tool, meanwhile, recently expanded its retrofit reCool coolant through system. Previously matched with live tooling on CNC lathes, the system can be now be used with static toolholders on Swiss automatic machines.
Iscar Metals has advanced its Groove Turn PCBN product line with the newly created IB10H and IB20H grades. IB10H is a fine-grain PCBN intended for continuous cutting, while IB20H, composed of fine- and medium-grain particles, offers a good balance between wear and impact resistance to withstand more severe cutting conditions. The failure mode with any PCBN should be gradual edge wear—not sudden cracking or rupturing.
To provide the rigidity needed for machining hardened steel parts, INDEX’s C100 and C200 turning machines feature the SingleSlide, a slideway with two degrees of freedom in one plane.
Cutting tool material consisting of polycrystalline cubic boron nitride with a metallic or ceramic binder. PCBN is available either as a tip brazed to a carbide insert carrier or as a solid insert. Primarily used for cutting hardened ferrous alloys.
Workpiece is held in a chuck, mounted on a face plate or secured between centers and rotated while a cutting tool, normally a single-point tool, is fed into it along its periphery or across its end or face. Takes the form of straight turning (cutting along the periphery of the workpiece); taper turning (creating a taper); step turning (turning different-size diameters on the same work); chamfering (beveling an edge or shoulder); facing (cutting on an end); turning threads (usually external but can be internal); roughing (high-volume metal removal); and finishing (final light cuts). Performed on lathes, turning centers, chucking machines, automatic screw machines and similar machines.
Machining grooves and shallow channels. Example: grooving ball-bearing raceways. Typically performed by tools that are capable of light cuts at high feed rates. Imparts high-quality finish.
Available in two major types: tungsten high-speed steels (designated by letter T having tungsten as the principal alloying element) and molybdenum high-speed steels (designated by letter M having molybdenum as the principal alloying element). The type T high-speed steels containing cobalt have higher wear resistance and greater red (hot) hardness, withstanding cutting temperature up to 1,100º F (590º C). The type T steels are used to fabricate metalcutting tools (milling cutters, drills, reamers and taps), woodworking tools, various types of punches and dies, ball and roller bearings. The type M steels are used for cutting tools and various types of dies.
GenSwiss’ recently released its Ti-Loc SwissClamp System “for rotary tooling in Swiss machines … it can be used for milling and slitting operations that utilize ER collets for tool holding,” explains Laprade.
“Swiss machines have three work holding devices in them if you don’t include the bar feed collets. The headstock collet, the guide bushing (which is what the stock feeds through during the cutting and is used for support), and the pickoff or sub-spindle collet which takes a parted-off work piece and can hold it for secondary operations on the sub spindle side of the machine.
“At GenSwiss we recommend micro-thin PVD coatings that don’t change the edge conditions of the cutting tools when applied to them,” adds Scott Laprade, marketing manager, Genevieve Swiss Industries, Inc. (GenSwiss). “When working with small diameter parts you want the edges to remain as sharp as possible to prevent pressure build up which can lead to deflection of the work piece. Some coatings and processes deposit a ‘bead’ of coating on the edge of the insert which can round it off by up to a thousandth of an inch.”
Number of axes along which a robot, and thus the object it is holding, can be manipulated. Most robots are capable of maneuvering along the three basic Cartesian axes (X, Y, Z). More sophisticated models may move in six or more axes. See axis.
Various work materials that are through-hardened include HSS, die steels, bearing steels and alloy steels. Only ferrous metals are casehardened and that process is typically reserved for low-carbon steel. Casehardening produces a hard, wear-resistant exterior over a tough core. Parts made from hardened steels include arbors, axles, link components, driving pinions, camshafts, gears, bushings, transmission shafts and bearings.
Exsys Tool places its expertise with tooling for Swiss-type machines front and center. The company highlights its Decoflex tooling system for interchangeable tools.
Some common groove features for hardened steel parts are simple square, profile and plunge grooves. Typically, grooved parts require a fine surface finish because there is a mating part or an O-ring or snap-ring groove. “The applications are split between internal and external operations, but the majority of applications require finishing passes,” said Mark Menconi, product specialist for Mitsubishi Materials, Schaumburg, Ill. “The finishing passes range from a slight touch-up with a low DOC near 0.010 " to a full finishing pass near a 0.020 " DOC.”
Insert shape also plays a big role in Swiss-type turning “since we normally do not rough and finish turn parts. Parts that have undercuts, larger grooves, angles into smaller diameters, and other features like that, are studied to see if a different tool can provide the entire profile in one turn. If not then we have to look at segmenting the part into sections to process,” says Paoletta.
“PVD coatings are most common due to the reduced heat factor in small part machining—small contact diameter, lighter feeds and good cooling. The required sharper cutting edges also dictate that PVD be used,” echoes Burton.
Mitsubishi Materials USA Corp.’s GY series Tri-Lock modular system reportedly offers rigidity equal to that of an integral insert holder. The system secures the grooving blade to the holder in three directions: the periphery and front and top sides. Two features decrease insert movement during grooving. The convex “V” formation eliminates side-to-side movement, and the safety keys eliminate forward movement caused by cutting forces when plunging.
There’s a general consensus that when it comes to designing tooling for Swiss-type turning, coolant through is preferable to flood coolant. Coolant through tools utilize high pressure (H.P.) for delivery.
“In Swiss applications where the parts and work envelope are generally smaller, through coolant when and where available is always a better option than relying on flood coolant,” says Garfield.
Casehardening is a simple method of hardening low-carbon steel whereby carbon is added to the outer surface of the steel to a specific depth. Problems can arise when the groove depth exceeds the thickness of the casehardening because the grooving insert transitions from a harder material to a softer one. Therefore, toolmakers have developed several grades for various types of materials.
Main body of a tool; the portion of a drill or similar end-held tool that fits into a collet, chuck or similar mounting device.
Sumitomo’s holder for CGA-style inserts has a top clamp and a side screw to enhance stability and tool life when grooving hardened steel.
No matter what kind of groove they are making, shops that previously relied on grinding for finishing hardened steel parts can improve productivity by transitioning to grooving with PCBN tools. They achieve comparable tolerances while dramatically reducing machining time. CTE
“You can cut 45- to 50-HRC material effectively with CBN, but you have to adjust the geometry,” Drape continued. “Typical CBN is manufactured with a negative land on the cutting edge. On softer materials with that negative land, the CBN is going to get pulled out of the material and then you lose tool life. If I use a softer CBN and adjust the geometry, I can have very good success cutting 45- to 50-HRC material.”
PCBN grades are evolving to cover a wider application range. Harder grades allow for elevated speeds while tougher grades can run in more unstable environments. Different grades of PCBN are also available for continuous or interrupted cutting. Because PCBN is brittle, a sharp cutting edge would start to chip when machining hardened steel, according to Sumitomo’s Maton. “We have to protect the edge, especially when interrupted cutting where the edge prep is much larger and at a greater angle than when continuous cutting.”
Sumitomo has introduced BNC30G, a coated PCBN grade for parts with interruptions. For continuous grooving, the toolmaker recommends its general-purpose BN250 grade. “With the continuous cut, you’re in the cut for a long time, generating a great amount of heat, so you need a high wear-resistance grade,” Maton said. “With interrupted cutting, you are coming in and out of the cut, banging the corner of the insert. Therefore, you need a very tough grade to withstand the interruption, and a coating helps the tool last longer.”
“Customers don’t always want to change the insert when going from harder to softer, so we have to find the next best tool for the operation,” said Duane Drape, national sales manager for HORN USA Inc., Franklin, Tenn. “If they use carbide, they have problems with the insert wearing too quickly on the harder outer casing. If they are cutting the softer area with CBN that was made for cutting very hard material, it would be destroyed. So we work on a compromise. We may work with a very hard carbide with a super lubricated coating or a soft CBN grade with an edge prep that is suitable for cutting rather than for hard machining.
The new Walter Cut G1011-P grooving tool from Walter USA, which can be used in Swiss-type turning, is internally cooled. “The G1011-P is designed so the coolant stream is released very close to the cutting edge, guaranteeing the best possible effect of the coolant, no matter what the supply pressure is,” says Kurt Ludeking, product manager of turning at Walter USA. “Compared to an external coolant supply, this ensures coolant at the cutting edge throughout the cut, especially important in deep, narrow grooves and parting operations
To sum up, Laprade cites an old retail truism. “Swiss tooling is a very ‘get what you pay for’ type of product. When you’re trying to continuously ‘split tenths’ you want something that is high quality and more importantly, repeats each time a job is set up or when a tool is changed. A good tool or tooling system will eliminate the need for an operator to chase a tolerance because the tooling wasn’t intended for it or is poor quality,” notes Laprade.
“Maximizing the envelope is crucial given the tooling requirement to complete a part versus space provided,” adds Jim Garfield, regional sales manager, at Horn USA. “Swiss type multi-function tools can reduce the number of tools/holders required as well as reduce cycle times. Quick-change Swiss holders can reduce downtime when changeover is necessary due to tool wear or new part set up. Repeatability of center height when changing insert/tools is of utmost importance,” he adds.
“Decoflex is a modular tooling system specifically designed for Swiss turning head stock machines…we have introduced a multi-headed collet chuck that will work in both directions of the spindle simultaneously,” says Scott Leitch, marketing manager with Exsys.
Crystal manufactured from boron nitride under high pressure and temperature. Used to cut hard-to-machine ferrous and nickel-base materials up to 70 HRC. Second hardest material after diamond. See superabrasive tools.
Metal-removing edge on the face of a cutter that travels in a plane perpendicular to the axis. It is the edge that sweeps the machined surface. The flat should be as wide as the feed per revolution of the cutter. This allows any given insert to wipe the entire workpiece surface and impart a fine surface finish at a high feed rate.
Sumitomo’s holders for CGA-style inserts have a top clamp that pulls an insert back into the pocket, and the holders also use a side screw to help enhance stability and tool life. “We only offer it for hard grooving,” said Rich Maton, assistant manager, engineering department for Sumitomo. “If you have an insert that is moving in the pocket, over time the insert will wear and tool life will vary, which is especially significant for the high-productivity requirements of the automotive industry, where going from 50 to 100 or 150 pieces per edge makes a huge impact.”
Industry experts were also asked about grades and geometries for Swiss-type turning tools. “A grade specifically for use in Swiss-type turning is WSM21, a mono-layer PVD coating that is designed to withstand the low cutting speeds often encountered with small diameter components. Grades with thinner PVD coatings and sharp edges are generally best,” says Ludeking. “Although there aren’t any specific Swiss-turning geometries, those with aggressive chip control for light feed rates and depth-of-cut are often best for Swiss-type operations.”
Process of increasing the surface hardness of a part. It is accomplished by heating a piece of steel to a temperature within or above its critical range and then cooling (or quenching) it rapidly. In any heat-treatment operation, the rate of heating is important. Heat flows from the exterior to the interior of steel at a definite rate. If the steel is heated too quickly, the outside becomes hotter than the inside and the desired uniform structure cannot be obtained. If a piece is irregular in shape, a slow heating rate is essential to prevent warping and cracking. The heavier the section, the longer the heating time must be to achieve uniform results. Even after the correct temperature has been reached, the piece should be held at the temperature for a sufficient period of time to permit its thickest section to attain a uniform temperature. See workhardening.
“Hard,” however, is a moving target. Some consider materials from 40 to 55 HRC to be hard, while, for others, hard is 58 to 60 HRC and harder, which is where PCBN comes in.
Crystal manufactured from boron nitride under high pressure and temperature. Used to cut hard-to-machine ferrous and nickel-base materials up to 70 HRC. Second hardest material after diamond. See superabrasive tools.
“When turning the O.D. of a part, H.P. coolant pays big dividends on gummy/hard materials or long cuts where stringy chips are a problem,” says Paoletta.
Grooving hardened steel requires harder and more wear-resistant cutting tools with appropriate tool geometry. The trick is to know whether to apply carbide, ceramic or PCBN inserts. “For an application less than 50 HRC, I almost always choose carbide,” Schmitz said. “Ceramics are a very economical choice for applications from 50 to 58 HRC. CBN should not typically be considered until the hardness reaches 58 HRC. This is where it performs best.”
CBN works well in such hard materials because instead of cutting the material, CBN molts the material at the tool/workpiece interface.
About the Author: Susan Woods is a contributing editor for CTE. Contact her by phone at (847) 973-2271, or by e-mail at susan@jwr.com.
Another option is changing the cutting parameters. “Once you cut through that casehardening, you can be more aggressive,” said Index’s Economan. “If the case depth only goes down to 0.005" or 0.0010", then after that you should increase the cutting parameters to appropriate levels with either the same tool or a different one.”
For induction-hardened, or casehardened, parts, the outer, hardened surface, can be as much as 1.5mm thick, and up to 58 to 60 HRC, while the undersurface is typically much softer. In situations like this, it is important to ensure the majority of the cut happens below the hardened, outer surface.
Steel containing specified quantities of alloying elements (other than carbon and the commonly accepted amounts of manganese, sulfur and phosphorus) added to cause changes in the metal’s mechanical and/or physical properties. Principal alloying elements are nickel, chromium, molybdenum and silicon. Some grades of alloy steels contain one or more of these elements: vanadium, boron, lead and copper.
Generic term covering several processes applicable to steel that change the chemical composition of the surface layer by absorption of carbon, nitrogen or a mixture of the two and, by diffusion, create a concentration gradient. Processes commonly used are carburizing, quench hardening, cyaniding, nitriding and carbonitriding.
As Swiss-type turning edges towards the mainstream, cutting tool companies continue to provide a steady stream of appropriate tools. Such tools have to be able to function in the confined work envelope characteristic of Swiss-type machines.
Horn, among other cutting tool companies, has new offerings for the Swiss-type turning sector. “Although Horn has traditionally been oriented towards small part Swiss type machining, we have introduced new tooling dedicated to Swiss-type turning grooving and milling applications. A recent introduction to our existing 274 line was the System 274 ‘µ’ finish for micro turning, grooving and back turning. In addition, our Graf line of Swiss tooling offer numerous options for holding with round shank holders and height adjustable quick change holders for most Swiss type machines, i.e. Star, Miyano and Citizen,” says Garfield.
“Coolant delivery can be the key to success and direct delivery via coolant nozzles built into the tools can have benefits of better chip control and cooling of the component and chips,” says Kevin Burton, product specialist at Sandvik Coromant in Mississauga, Ontario.
Rigid machine tools with adequate power are a must for hard grooving. “The more rigid and powerful machine you have, the more aggressively you can cut hardened material,” Economan said. “For applications involving machining materials harder than 50 HRC, many light-duty machine tools won’t hold up to the demanding cutting conditions. This holds true when the machining requirements exceed what the machine is capable of, as far as horsepower, torque and especially rigidity.”
Toolholders for grooving inserts should be as short as possible to minimize overhang, which increases rigidity. And while solid, or integral, holders are typically better suited for hard grooving, according to Matthew Schmitz, national product manager—GRIP Products for Iscar Metals Inc., Arlington, Texas, Iscar offers modular systems as well.
“On the I.D, using coolant-through drills for instance, can gain you a 2x feedrate over a standard carbide drill or 3x to 4x a cobalt drill, while you can also increase your SFM for the tool,” he explains.
“There are many tools that were designed with the Swiss machine in mind, due to the limited tooling space and stations,” says Douglas Paoletta, president and owner, Encompass Swiss Consulting in Richmond Heights, Ohio. “Iscar’s Pentacut insert, which is a five-sided indexable tool, is one. One of the first ‘back turning’ tools, and still one of the best, is the Kyocera ABS/ABW series tool. Kennametal has one of the best ‘quick change series’ tools called the KM Micro,” adds Paoletta, whose company offers on-site training for shops and manufacturers interested in Swiss-type machining.
A type-S117 HORN PCBN-tipped insert finishes the width of the groove on this gear. Stock removal is approximately 0.15mm to 0.2mm. To obtain a fine surface finish, the insert has a wiper flat on both side-cutting edges.