Cutting the tough stuff

Titanium has long been used in the aerospace industry, but increasingly, other sectors are taking notice of this tough-to-cut, but durable material. That’s because the material offers higher tensile strength, is stronger than steel but approximately 42 per cent lighter, and is highly resistant to corrosion, particularly against oxygen.

Use of titanium is growing in many sectors such as medical (e.g. human implants such as joint replacements, dental implants, surgical instruments), automotive (brake and exhaust systems), optical, sports equipment (e.g. bicycles and golf clubs), architecture and jewellery.

According to Iscar Tools in a recent article, “Titanium Machining Solutions for the Medical Industry,” titanium 6AL-4V “is the most popular material for medical implants due to its light weight, high strength and biocompatibility. Titanium implants are compatible with magnetic resonance imaging and computed tomography imaging procedures, and do not cause any interference with those procedures, should they be required after the implant is made.”

The toughness characteristic of titanium requires higher cutting forces than other typical metals used in manufacturing.

“Think of it as stainless steel but with a tougher, stringier chip, plus a strong tendency for break-out at tool entry and exit points,” notes Iscar. “Carbide tools don’t need to be coated because they don’t react chemically with titanium as they do with steel, but they do need to be very sharp. Also, to protect against overheating at higher machining rates, PVD coated grades are recommended.”

Stephen Jean, milling products manager for Emuge Corp., West Boylston, MA, says more manufacturers are beginning to use titanium and other challenging materials.

“The demand for parts and components machined from these materials is on the rise, but the same special properties, like high heat, chemical and abrasion resistance, that make these materials desirable for use in extreme-service applications, also make them difficult to machine. “Typically, these materials burn up cutting tools.”

David Goulborune, development manager for drilling products at Dormer Precision, Crystal Lake, IL, says high temperature resistant alloys such as titanium are difficult to machine for two reasons.

“Firstly, they generate high cutting forces during machining, leading to high pressure and heat, which in turn tends to result in work hardening. Secondly, because they are able to withstand high temperatures, the heat generated during drilling is retained within the workpiece and transferred to the tool, resulting in premature drill failure.”

Here’s a look at what several cutting tool suppliers offer for titanium cutting.

Emuge

Emuge Corp.’s TiNox-Cut is a new series of end mills that provide what the company claims is exceptional tool life when machining challenging materials such as nickel alloys like Inconel and Stellite, all grades of titanium, and tough stainless steels like Super Duplex, materials used extensively in the aerospace, power generation, medical, chemical and food industries.

The new end mills feature a high heat resistant, lubricious coating and an optimized cutting edge design. This provides long tool life by minimizing friction and evacuating chips efficiently, which is especially important in tough, long-chipping materials. In addition, the tools are made from an extra-tough carbide grade to maximize wear resistance.

For maximum effective cutting lengths, these end mills feature reduced neck diameters. Offering superior machining repeatability and safety, the new end mills combine a tight, h5 shank tolerance with a specially roughened surface finish to maximize toolholder clamping potential.

These cutting tools are well suited for both roughing and finishing operations and consist of three designs: two four-flute variations for both roughing and finishing, and a five-flute extra long finishing tool.

TiNox-Cut roughing/finishing end mills are available with flat ends or with a selection of corner radii. For even more efficient chip evacuation, the four-flute end mills are available with internal coolant/lubricant capability. The roughing/finishing versions are available with a serrated profile for effective chip breaking during roughing operations.

The five-flute finishing end mills are also available with various corner radii, and feature length-to-cutting diameter ratios of three times D and four times D. The five-flute design offers added stability and minimal deflection in long reach applications.

The end mills range in diameter from 6 mm – 20 mm, depending on the design.

www.emuge.com

Ingersoll

Ingersoll has two recent product family introductions for cutting titanium: Finish-BallRush indexable fine milling ball nose end mills, and Hi-PosTrio indexable end mills and face mills.

The new Finish-BallRush tooling line features an ultra stable clamping system with excellent repeatability. A unique coolant delivery system enables coolant (or air blast) to be delivered to the cutting edge for what the company describes as “exceptional performance and productivity” on a wide range of materials from general purpose and die and mould applications to high temperature alloy aerospace applications. A complete range of cutter diameters in both inch and metric sizes are in stock along with standard, extended length and modular style shanks that complement the available grades and geometries.

The new Hi-PosTrio cutting tool line is available in three different insert sizes. Cutter diameters range from .625 in. up to 6 in. (15 to 152 mm). Each high positive three-edged insert incorporates a true helical geometry and each insert I.C. size provides a full range of corner radii from .015 in. up to .125 in. R (3.81 to 3.17 mm). These cutters are well suited to machining steel alloys and high temperature aerospace material with their high shear geometry, premium grades and aggressive ramping capabilities.

www.ingersollcuttingtools.com

Iscar

Machining titanium alloys requires cutting forces comparably higher than those required for machining steels. And titanium alloys present metallurgical characteristics that make machining more difficult than steels of equivalent hardness.

Carbide tools don’t need to be coated because they don’t react chemically with titanium as they do with steel, but they do need to be very sharp. Also, to protect against overheating at higher machining rates, a PVD coated grades such as IC908 -IC907- IC1008  are recommended.

Iscar has developed a broad line of miniature inserts specifically designed for titanium work.

The main characteristics these cutting tools have in common are very sharp edges, and honed or ground surfaces to produce a fine finish and deny a foothold for built-up edge. Virtually all are available in carbide grade 908, for decades the preferred grade for titanium work in the aerospace industry.

The company’s family of miniature titanium tooling now includes an endmill with extremely sharp edges, a bowl shape and honed surfaces; solid carbide drills as small as 0.8 mm with P geometry, and reamers with S geometry, four types of turning inserts with aggressive WF or MD chipbreakers and titanium versions of Jetcut parting tools. In the pipeline is a titanium version of the Tang-Grip heavy duty tangential parting tool.

The company has also designed specific lines of tools, inserts and chipbreakers for machining Ti6Al4V to achieve the precise tolerances required by the industry.

Milling operations: Solid carbide endmills with sharp cutting edges for bowl-shaped parts as well as deburring. These endmills can provide a 0.01 maximum honing for semi-finishing and finish operations. Iscar has also developed tools for machining both titanium and stainless steel, using a submicron base with a PVD coating. This allows the machines to run at high speeds and feeds.

Drilling: New solid carbide drills for diameters as small as 0.8 mm with sharp cutting edges and a P geometry. These tools are produced with Iscar’s submicron grade 908.

Reaming: New solid carbide reamers, from 1 mm diameter, are produced with sharp cutting edges and utilize an S geometry. They are available in the company’s advanced submicron grade 908.

Turning: Includes ground inserts, such as the VCET, DCET and the CCET, all with Iscar’s WF chipbreaker. For certain applications Iscar can offer the fine VCGT inserts with its MD chipbreaker for high surface quality.

Parting: The Jet-Cut system with 3 and 4 mm inserts is available in the submicron grade 908, providing high quality surfaces and extended tool life. The company says it’s in the development stage of a new HP system for its Tang-Grip tools.

www.iscar.ca

MAG IAS

New Cyclo Cut Max-Flute high performance end mills from MAG innovate titanium roughing with a 16-flute design capable of high removal rates at low torque. The high density end mills run at 2037 rpm and 231 ipm to achieve removal rates of up to 8 in.3/min with only 25 ft lb of torque and 9 hp.

When cutting titanium, 60 to 70 per cent of the heat generated is normally transferred to the tool, dramatically reducing tool life. Max-Flute tools use shallow, radial widths of cut, which transfers less heat to the cutting tool and allows higher surface speeds for roughing titanium, Inconel and other high temperature alloys that have traditionally required high torque at low rpm to achieve desired removal rates.

Used in conjunction with TrueMill software, Max-Flute end mills maintain a constant angle of engagement, making the radial cuts more consistent throughout the cutter path, increasing material removal rates and decreasing cycle times, while extending tool life. “The current approach to high speed machining involves taking very light cuts,” says Dan Cooper, product manager for MAG Regional Services. “The Max-Flute/TrueMill approach enables the machine to make heavier cuts at high speeds, and by using the maximum flute density available, maximum feed rates are achievable.”

Max-Flute tools are designed with a differential pitch on the tool flutes to break up harmonics and reduce chatter. “Titanium is very prone to chatter, which affects part quality, and can cause unpredictable tool failure,” adds Cooper. “By using extremely high feed rates and light radial cuts, we can remove a lot of material with very little risk of scrapping parts.”

mag-ias.com

OSG Canada

Aerospace manufacturing is a market that is constantly evolving due to increased performance demands and rising fuel costs. Exotic materials such as titanium alloys are being engineered into new designs to increase strength while reducing weight at the same time, thus lowering fuel consumption.

Tapping is often one of the last machining processes performed on these complex parts so tap failure can be an extremely costly event on a nearly completed part. Titanium alloys have historically been difficult to cut due to poor heat conductivity, strong alloying properties and work hardening tendencies.

With this in mind OSG Corp.’s tap engineers have developed a series of taps specifically for titanium alloy applications.

OSG Exotap VC10 Ti taps feature a proprietary Powdered Metal (HSS) substrate, TiCN coating, slow flute helix and strong cutting edge geometry for exceptional

wear and heat resistance, tap strength and effective swarf evacuation, claims the company. Eccentric radial relief reduces tap contact while threading, greatly reducing heat and eliminating “work hardening” of the work piece, a common problem with titanium alloys.

OSG VC10 Ti taps are available in Spiral Point (thru-hole applications) as well

as Spiral Flute (blind hole applications) in both inch sizes (2-56 to 1 in. UNC, UNF) and metric (M3-M12).

www.osgcanada.com

Precision Dormer

The Elect S drill range represent the first products launched by Dormer for the machining of materials known collectively as Heat Resistant Super Alloys (HRSA).

Including high temperature resistant alloys such as titanium, Inconel and Waspalloy, these materials can be difficult to machine, says David Goulbourne, Dormer’s development manager for drilling products. High cutting forces during machining leads to high pressure and heat and work hardening. This heat can result in premature drill failure.

In addition to internal coolant holes, several features of the Elect S drills combine to lower the occurrence of work hardening. These include a body back taper that promotes a free, continuous cutting action as well as high quality, accurate holes. A self centering 140° point angle, cylindrical margin and positive cutting edge geometry also work to minimize frictional cutting forces, leading to consistent tool performance and minimal work hardening.

Another key attribute of the Elect S drills is a Smooth-Flow coating that acts as a thermal barrier, protecting the substrate from the extreme heat generated at the cutting edge. This also has a low coefficient of friction, resulting in smooth and efficient chip evacuation and, in turn, extended tool life.

Available in two lengths to support drilling to 3 x diameter (R507) and 5 x diameter (R503), the drills will be of particular interest to anyone involved in the production of high value components or requiring a high degree of precision, such as aerospace subcontracting, oil and gas and nuclear industries.

www.precisiondormer.com

Sandvik Coromant

Sandvik Coromant has introduced two new grades for titanium milling as part of its CoroMill 690 cutter family. Together these grades amount to a new level of reliable long lasting performance, claims the company. Grades S30T and S40T are available for a variety of CoroMill cutters for face, shoulder, long-edge and high feed milling, plunging, profiling and slot milling.

S30T has been developed for productive titanium milling. It combines the properties of micro-grain carbide and a wear resistant PVD coating. This enables very sharp cutting edges that resist fatigue and micro-chipping and result in cutting edges that are preserved for longer times in cut at higher cutting speeds.

S40T is developed for difficult conditions. It combines high toughness cemented carbide with a thin CVD coating. The result is a grade that withstands vibrations and other difficult cutting conditions for longer times in cut. The wear is predictable, making the cutting edge gradually duller without breaking.

www.coromant.sandvik.com

Seco

Seco Tools has announced a new line of Super Turbo chamfer mills designed to provide high metal removal rates while reducing production costs. The new cutters use the same inserts and hardware as standard Super Turbo square shoulder mills, allowing manufacturers to increase the versatility of their operations without additional spare parts.

The new chamfer mills feature a high positive cutting rake angle and positive helix angle to reduce power consumption, resulting in freer cutting and reduced harmonics. The design increases tool life as compared to standard APxx style cutters, helping to reduce cost per part.

They use the same strong insert pocket design found in the rest of the Super Turbo family of products. The strong insert screws and thick, robust inserts offer increased reliability for fewer tooling changes.

Super Turbo chamfer mills are available in setting angles of 30°, 45°, 60° and 75°, with a depth of cut capability of 0.197 in. – 1.653 in. (5 mm - 42 mm), for production of the most common open or close to shoulder chamfers.

The new tools are available in Seco-Capto and Combimaster back-end options, with standard shell mill mounting styles in either inch or metric arbor holes. All versions include internal coolant channels.

As part of the Super Turbo mill family, the chamfer mills utilize the full range of Super Turbo insert grades, including Duratomic coatings, and geometries. This ensures that the tools apply across a wide range of materials and applications.

Seco Tools’ Turbo Mill offering is a comprehensive and versatile square shoulder milling product line that provides solutions for slotting, ramping, contouring, plunging, pocket milling and both circular and helical interpolation.

The family of cutting tools includes a choice of 13 carbide grades, three PCD-tipped grades and five geometries suited for a variety of materials, including steel, stainless steel, cast iron, hardened materials, high-temperature alloys and non-ferrous materials. Super Turbo’s unique inserts feature an optimized edge, advanced helix angle, large wiper flat and strong, highly positive rake angle to allow high productivity.

www.secotools.com

Walter USA

Walter Valenite has introduced three new geometries in the Sky·tec family to make turning titanium alloys (e.g. Ti6Al4V and others) much more cost effective and more reliable. Customer results have yielded tool life improvements of more than 150 per cent, claims the company.

The Sky·tec program has an optimized combination of substrate, coating and geometry working together to minimize crater wear and provide excellent chip control. The geometries include NFT for high cutting speeds, available in periphery ground or as-sintered versions. NMT is for medium machining with low cutting forces due to the curved cutting edge. This geometry handles unstable components and internal machining, and is available with as-sintered periphery. NRT for roughing offers a rigid geometry for high metal removal rates and is offered as-sintered periphery.

The inserts are available in the C, D, S and V styles with negative edge geometry. Two cutting tool grades include an uncoated grade WS10, and the PVD aluminum oxide coating (“PVD-Tiger”) WSM20. For the majority of applications, the uncoated WS10 is the first choice for machining titanium alloys.

For CNMG (80° corner angle) inserts in the NFT geometry, Walter offers a special feature: the 80° corner has the NFT finishing geometry, and the 100° corner has the NRT roughing geometry. Essentially, the user has the added benefit of two inserts in one, further reducing tooling costs.

www.walter-tools.com/us