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Extremely hard grade for brake disc machining

Cutting tool manufacturer Horn has launched a new product range for machining brake discs economically. It includes solid cubic boron nitride (CBN) ISO inserts, mainly used for cast iron machining, and CBN-tipped full-radius and shaped inserts. The grade has no metallic bonding phase and therefore has the highest hot hardness of all cutting materials. Stable tool carriers are included in the offering.

For machining applications on a brake disc, Horn offers a solid CBN ISO S insert with eight cutting edges. In conjunction with the tool holder, the system is suitable for roughing and finishing. The neutral design of the inserts fully utilises the number of cutting edges. It means that eight cutting edges per ISO insert are available for most turning operations.

Cutting speeds of well over 1,000 m/min, depths of cut of several millimetres and feed rates up to 0.7 mm/rev are typical when machining cast iron brake discs using a solid CBN insert. The tool system must be able to maintain high cutting performance and, above all, exhibit long tool life due to the cost per cutting edge of CBN. Depending on the operation and metal removal rate, well over 1,000 cast iron brake discs can be machined per insert corner.

Horn offers two different tool solutions for machining the heat dissipation grooves in the disc. The CBN-tipped S117 profile grooving insert is ideal in terms of speed and tool longevity for large batch production. During the process, each groove is produced in just under two seconds in a single operation. For greater flexibility, Horn's S229 tipped, full-radius inserts offer the option of copy turning the grooves in around four seconds. Regrinding and re-tipping are possible with both types.

The tool holder combines important criteria. The frictional connection between the carbide thrust pad and the insert occurs via a defined annular surface, preventing compressive stresses on the CBN insert. Engagement of the thrust pad in the bore of the insert pulls it into the seat of the tool holder, preventing clamping errors and increasing precision.