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BECKER Diamantwerkzeuge GmbH

Diamond cutting tools

PcBN - Scout

At a temperature of approx. 600°C the steel grade 1.2379 still has a hardness of about 58 HRc, the steel grade 1.7131 about 48 HRc, and the steel grade 1.3505 only achieves about 36 HRc. The original hardness of each steel grade had been about 62 HRc.

In order for all users to exploit the full potential of our extremely high performance PcBN cutting materials, the following explanations and hints are of importance.

As shown in our previous catalogue supplement we offer our 6 coated PcBN-grades in up to 8 different chamfer geometries per cutting material as well as in various tipping options (see here). This large standard range enables us to meet basically all imaginable application profi les ex stock.

Hard machining with PcBN

The cutting of hardened steel is generally referred to as hard machining. This cutting mechanism is a selfinduced hot cutting process. This requires a defi ned and high temperature of about 550 to 750°C on the cutting zone. This necessary temperature is being produced by the transformation of existing energies into heat. This energy is released in the form of cutting speed Vc, feed rate fn, depth of cut ap as well as the chamfer geometries A-H of the PcBN cutting edges. Cooling is generally not required. Below we have illustrated 3 diagrams of hardness values. You can make out the decreasing hardness with the rising of the temperature. However significant differences are shown.

During the self-induced hot cutting process with our PcBN-grades the ideal hardness in the shear zone is at 40 to 45 HRc. This means that in such a case different cutting temperatures between 550°C up to 750°C are necessary.

In order to produce and maintain the ideal cutting temperature in the shear zone, it is obligatory to strictly stick to three particularities:

  • the thermal conductivity of the PcBN-grade used (55% - 65% CBN)
  • the applied chamfer geometry A-H, and also the positive top rake geometry (see here)
  • as well as the hardness diagrams (hardness diagram with rising temperature)

In order to give you professional advice on our standard range for the intended application, the following checklist has to be strictly respected:

  • precise specifi cation of the steel grade and its hard ness HRc
  • the required surface fi nish Ra has to be determined as well as the depth of cut
  • please decide if your cut is continuous to slightly-interrupted or medium to heavily-interrupted

Please select the PcBN grade as described on Page PcBN-cutting materials.

Now please choose the according chamfer geometry for the required surface fi nish, as shown in our diagrams on page cutting data Application range.

100Cr6 – HRc 62
ap= 0.25, fn = 0,1 mm
interrupted cut
required Ra = 0.6
PcBN grade = PBC-40S
chamfer “D” at Vc 160 m/min
insert: CNGA 120408-D-40S-4SC

Soft machining with PcBN

Soft machining encompasses the cutting of all materials in their natural hardness without any hardening process or similar applied. Thus the result means not any microstructural transformation has occurred. How ever it is absolutely necessary to keep materials in mind (super alloys, titanium etc.) that require a very high cutting temperature of 700 to 1,110°C, which can only be generated with the cutting material grade PcBN.:

On page cutting data Application range we have listed different application examples each explained by a simple diagram. On the left-hand side we have indicated the recommended cutting speed, and on the lower lines the according feed rate and depth of cut.