Ceramics, PCBN, PCD, CBN, cermetscan provide genuine machining

advantages over conventional carbidegrades, provided they are appliedcorrectly (see box item, page 40).

So what’s hot and what’s not? Ofcourse everyone has their own opinionson this, with cutting tool suppliersfocusing on those areas where mostgains can be made.

CERAMIC NICHEFor instance, according to WNT, ceramiccutting materials will remain as nicheproducts with a relatively narrowapplication area such as automotive.“We are finding that the development ofcarbides is diminishing the advantagesthat ceramics once had,” says thecompany’s business developmentmanager, Adrian Fitts. “This iscompounded by the time required todevelop the practical functionality ofceramic materials, an area that depends,to a much greater extent than carbide,on detailed knowledge.”

However, WNT predicts that PCBNand CBN will have a bigger role to play inmetalcutting due to their sandwichmethod of manufacture. This allowsinserts to be pressed on both sides,simplifying the manufacturing processconsiderably. That said, as withceramics, the major problem withboron nitride is the correct

application of the insert. Finally, the development of PCD has

seen WNT introduce PCD inserts withchipbreakers for use in non-ferrous anddifficult-to-machine materialapplications. The design of the newchipbreakers ensures high levels of chipcontrol, particularly on the neweraluminium materials – for example, verysoft, low quality, difficult-to-machinealuminium such as HE30. However, thisdevelopment is not to the detriment ofthe conventionaladvantages of PCDtooling, such as“no burr” andlong tool life.

Confirming the predictions of WNT,Jacob Harpaz, president of the IMCGroup (which includes Iscar, Ingersolland TaeguTec) also says that the globaluse of cutting tools is changing in termsof tooling materials. “Between 2000 and2005, the global market for PCD usageincreased from $230 to $460 million,prompted by overwhelming growth inthe automotive sector and the use of castiron and hard ferrous materials in thisindustry,” he says. “This growth is alsoreflected by CBN usage rising from $190to $380 million.”

THE PCBN FACTORSince the mid-1980s, PCBN cutting

tools have gained rapidacceptance in the automotive

industry. Having long tool life andthe capability of operating at high

cutting speeds, PCBN cutting toolshave helped automotive companies

increase capacity on existing equipmentwhile improving workpiece quality.

The cubic boron nitride crystal’s highhardness, thermal stability and chemicalinertness provide an extremely efficientcutting tool. Generally speaking, PCBNmachining operations should be run dry.PCBN is hard enough to resistdeformation from the heat generated in

machining, but it is also brittleenough to crack from the

thermal shock ofcoolant. That is

especially true inthe case ofinterruptedcuts – never

use

TOOLING

Exotic substratesCeramics, PCBN, PCD, CBN and cermets. Steed Webzell examines

the world of exotic cutting tool substrate materials

39

www.machinery.co.uk ● March 2007

Right – ITC’s 2111 two-flute PCDendmill is targeted at abrasive non-ferrous materials used in themotorsport sector. Above – Seco’sCBN050C, claimed as the world’s first multi-format PCBN grade

Tooling_2.qxd 22/2/07 12:22 pm Page 39

coolant in PCBN operations where thecut will be interrupted.

One all-new PCBN grade isCBN050C, which Seco is declaring to bethe world’s first multi-format PCBNgrade – available in solid, full-faced,multi-tipped and single-tipped formats.Seco has also introduced CBN400C,another new PCBN grade for machininggrey cast iron and abrasive steelcomponents used extensively in theautomotive sector, such as engine blocks,cylinder heads, valve seats, valve stems,fuel injector nozzles, fuel pump barrels,crankshafts, camshafts, transmissioncasings, gears and shafts, as well as brakediscs, brake drums, clutch plates, clutchsleeves, axle casings, CV joints and otherpowertrain components.

Seco says that its PCBN tooling offersa 10-fold increase in cutting speed and a100 per cent increase in feed rate whenface milling grey cast iron engine blocksin comparison with tungsten carbidetools. Surface finish and flatness are alsoimproved – essential in relation to thehead gasket sealing surface.

But exotics are not all about theautomotive sector, as proved by NTKCutting Tools, which has many years’experience in delivering various cuttingtool solutions, and now offers a selectionof exotic tooling substrates for theaerospace industry. The company’s newWA1, for example, is a whisker-reinforced ceramic grade developed byadding silicon carbide to alumina. Itoffers extreme fracture toughness andnotch resistance for applicationsrequired typically in the aerospace sector.

NTK has also just launched its newSX1 silicone nitride ceramic grade forcast iron machining (pictured, left). Ithas been developed to reduce the notchwear of ceramic in heavy roughingoperations and can function at highoperating speeds under dry cuttingconditions. This is enabled by the

reduction of a binder element in thesubstrate – effectively a change from aninter-granular phase of silicon nitrideparticles to a higher melting pointcompound.

ABRASIVE TARGETSClosely allied to aerospace is the UK’sbuoyant motorsport sector and it is herethat ITC has enjoyed considerable recentsuccess. Its new 2111, 2102 and the 4081series of endmills are targeted at themachining of graphite, metal matrixcomposites, Kevlar, carbon fibre andother abrasive materials used commonlyin the motorsport industry.

The 2111 series is a high performancetwo-flute PCD endmill with a solidcarbide shank and necking for extrareach. Similar to the 2111, the 2102 serieshas a solid carbide shank with PCDbrazed tips for enhanced tool life andproductivity when machining carbonfibre parts.■■

� Enter 120 atwww.machinery.co.uk/enquiry

TOOLING

40

March 2007 ● www.machinery.co.uk

Ceramics – Typical applications include general machining ofcast iron, heat resistant alloys and hard materials up to 65 HRc, as well as semi-finish and finish machining of ductilecast iron and high speed machining of cast iron. Ceramics canachieve high metal removal rates and so are well suited tolarge components such as cast iron truck hubs, turbine shaftsand steel mill processing rolls.PCBN (polycrystalline cubic boron nitride) – Most associatePCBN with the machining of hardened steel parts (above 45 HRc) or superalloy components in the automotive industry,such as the rough boring of cylinder liners or theturning of engine parts such as gears, shaftsand bearings. However, it is alsoeconomical to use this substratematerial to machine cobalt or iron-based powdered metals, as well asdifficult cast iron alloys previouslyprocessed exclusively by grinding.PCD (polycrystalline diamond) –Typical uses include face milling ofaluminium alloys and other non-

ferrous materials where high chip resistance is required. It isalso used for medium-high silicon-aluminium alloys wheretools need to display abrasion resistance. Many automotivecomponents benefit from this grade of cutting tool includingcylinder heads, rocker shafts, transfer cases, intake manifoldsand oil pump bodies. Optimised cutting conditions wouldtypically be in the region of 12,500 rpm spindle speed at 0.1 mmper tooth feed.CBN (cubic boron nitride) – Suited to high depths of cut in castiron machining, high speed machining of cast iron, hard

machining of roll forms, as well as milling and turningof hardened steel and sintered hard materials.

Cermets (hybrid ceramic and metalcarbides) – Typical applications include

finish and semi-finish machining ofsteels, ductile iron and sintered alloys,

bearing race machining, and highspeed finish machining of ductilesteels. It is also well suited togrooving stainless steels andnodular irons.

Which for what?

Tooling_2.qxd 22/2/07 12:23 pm Page 40