Glossary

Bore machining on NF metals and NF alloys

In the manufacture of components made of NF metals and alloys, in particular in fully automatic operation, polycrystalline diamond cutting tools offer great economic advantages. Alternative conventional tool designs are being used less and less frequently in these applications. PCD tools have won through in particular because a change has occurred in the cost calculation for cutting tool materials. Previously, the costs of cutting (e.g. the insert price) were considered and compared independently, but today, with the use of different cutting tool materials, the cutting tool material costs per workpiece, i.e. the machining costs, are compared in relation to each other. The advantages of PCD tools, namely the high material removal rate, long service life and thus far less frequent tool exchange, as well as the high reproducibility of machining results, play a particularly important role here.

Bore machining on NF metals and NF alloys – examples

Fine machining of tappet bores

Fine machining of injection pump bores

Internal turning and facing on hard cast material

In addition to the performance of the cutting inserts used to achieve economical rate of metal removal, the good service life properties of the cutting edges is an important factor in ensuring they do not quickly blunt, which would result in a reduction in cutting force and a greater displacement of the drill spindle, which adversely affects the geometric precision of the bore surfaces to be created. These tasks are often made more difficult by the fact that the bore surfaces have cut interruptions in the form of radial bores or axial grooves, which cause high dynamic loads on the cutting edges as well as vibrations in the system. CBN cutting inserts have also proved their worth in these applications, thanks to their good performance and service life properties.
Internal turning and facing on hard cast material – examples for CBN machining

Bearing seat, cast steel roller sleeve ( 18% Cr )

Cast steel part, raw, with axial groove ( G-X 165 CrMoV 12 )

Particular features

Unlike PCD and diamond, CBN does not react with the carbide-formers present in these materials. The cutting heat generated is similarly not a problem for CBN, as this cutting tool material only reacts with oxygen as of a temperature of approx. 1200° C and thus has unrivalled hot hardness.
"Super-alloys” used in the building of aircraft and reactors with a marked austenitic phase and at the same time high toughnesses are areas in which CBN tools currently reach their limits. A cutting test must be used here on a case-by-case basis to clarify the situation. Typical materials of this kind include high nickel alloy materials such as Inconel 718 or Nimonic.

Basic properties

CBN, which in hardness is only surpassed by diamond, was developed to cut materials that cannot be machined with PCD or monocrystalline diamond. The main application areas here are currently iron materials with a hardness as of approx. 45 HRC, grey cast iron, Cr chilled castings and and alloys for wear parts on a cobalt, nickel or iron basis.

Manufacturing process

Cubic boron nitride ( CBN ) is a high-performance cutting tool material made of a polycrystalline mass of cubit boron nitride grain. With its high-temperature, high-pressure, sinter method, the production of CBN matches that of PCD.

 

CBN technical properties, comparative table

• Typical areas of use and applications
• Iron materials as of 45 HRC
• Cast steels: grey cast iron, nodular cast iron, Cr chilled castings
• Carbides: sintered carbide (different types, trial machining usually required)
• Sintered steels
• Cold- and hot-work steels
• Ball bearing and spring steels
• Surface-hardened parts, welded-on elements and hard-facings
• Wear parts: cobalt, nickel and iron basis

Comparative table of technical properties

CBN usage parameters

Cutting speed Vc (m/min) during turning

Cutting speed Vc (m/min) during milling

Cutting speed Vc (m/min) during milling

Cutting speed Vc (m/min) during millingFeed speed S (mm/u) during turning or Sz (mm/tooth) during milling

Information on standard equipment

Information on laser chip breakers and cutting tool material types

PCD

We use PCD types on a compound basis for equipping the ISO indexable inserts and fullface inserts. An approx. 0.5 mm thick diamond layer of medium grain size is sintered onto a carbide base. These compounds are hard soldered onto the carrier indexable insert or, in the case of fullface inserts, are processed further in their original state. The cutting edge length in PCD standard inserts is 4.0 mm in the reusable version and 2.5 to 3.0 mm in the disposable version. For details, please see the relevant article descriptions. PCD is suitable for both wet and dry machining, and if the tool is configured accordingly, minimal lubrication is required.

PCD with lasered chip breakers

3 different lasered chip breakers are possible with PCD reusable inserts.
LWLS-01 F for finishing
LWLS-02 M for medium machining
LWLS-03 R for roughing

CBN

For the standard equipping of CBN cutting inserts, we use four different qualities, which differ in their application range.
Type 1: LWC – 100 This type is best suited for the roughing and medium machining of grey cast iron, nodular cast iron, singered steels, CrNi alloys and coating alloys. It is also still the first choice for all milling operations.

Type 2: LWC – 200 The first choice for fine and ultrafine machining of hardened steels, but also all other iron materials as of a hardness of approx. 45 HRC. Turning operations with a smooth cut and slightly interrupted cut.

Type 3: LWC – 250 The first choice for fine and medium machining of hardened steels, but also all other iron materials as of a hardness of approx. 45 HRC. Turning operations with slightly or averagely interrupted cut.

Type 4: LWC – 350 The first choice for fine and medium machining of hardened steels, but also all other iron materials as of a hardness of approx. 45 HRC. Turning operations with averagely or severely interrupted cut.

The cutting edge length in CBN standard inserts is 4.0 mm in the reusable version and 2.5 to 3.0 mm in the disposable version. For details, please see the relevant article descriptions.

The size of the cutting edge chamfer is 0.20 x 20° for reusable inserts and 0.15 x 15° for disposable inserts.

For both CBN types, dry machining should be aimed for to avoid heat interactions on the inserts and chemical effects from water or oil on the cutting edges.

PCD – machining examples

Machining of composite materials

Composite materials based on wood, plastics or fibre-reinforced materials and alloys are increasingly being used. Higher performance and quality requirements mean that tool design must also be continuously improved. These criteria are met through the more widespread use of polycrystalline diamond cutters.
The materials, fibres and fillers added during surface treatment and coating naturally result in properties that make the machining of these materials more difficult. The careful selection of the cutting tool material is an absolute prerequisite for creating an effective tool.

Machining of composite materials – examples

Milling of chamfered grooves

Turning of GRP workpieces

Particular features

The hardness of the PCD layer is practically the same as that of monocrystalline diamond and is coupled with toughness, excellent mechanical wear resistance and high thermal conductivity. In addition, PCD is an isotropic solid with orientation-independent hardness and a wear property without cleavage planes.

Basic properties

The combination of the excellent hardness and wear properties of the diamond with the strength properties of the carbide makes PCD a cutting tool material that permits metal cutting performance up to the very limits of today's the machine tools and metal cutting systems.

Manufacturing process

Polycrystalline diamond (PCD) is a synthetically produced, extremely strong, coalesced mass of randomly oriented diamond crystals produced through the sintering of carefully selected diamond grain at very high temperatures and extremely high pressures. The sintering process, strictly controlled within the diamond-stable range, produces an extremely hard isotropic structure. PCD cutting inserts have a carbide base onto which the polycrystalline diamond layer is bonded during the sintering process.

Typical areas of use and applications

• Al and Al alloys
• Non-ferrous metals: copper, brass, bronze, zink, magnesium alloys, silver, Carbide: presintered (green) carbide
• Cast steels: grey cast iron, nodular cast iron, Cr chilled castingsPlastics and rubber
• Plastics and rubber
• Ceramic
• GRP/glass fibre composite materials
• CRP / carbon fibre composite materials

Comparative table of technical properties

PCD usage parameters

Cutting speed Vc (m/min) during turning

Cutting speed Vc (m/min) during milling

Cutting speed Vc (m/min) during milling

Feed speed S (mm/u) during turning

Feed speed Sz (mm/tooth) during milling