This paper .<:hows the results of investigations performed in the brittle materials microcutting at the Faculty of Mechanical Engineering, Belgrade University. The interactions between a single diamond grain and the machined granite are analyzed. The change in the normal cutting force as a function of grain penetration speed and depth was experimentally established in microcutting of two types of granite originating from Serbia. Based on the grain traces on granite and the generated cracks, the critical grain penetration depth for the formation of brittle fracturing was established. The experiments are intended to assist in the optimization of the grinding process as technology dominant in the granite finishing.

This paper offers an experimental study of the microcutting mechanisms in marble grinding to aid the optimization of the marble grinding process. The necessity for investigating these mechanisms is dictated by the increased use of marble in many applications and the fact that grinding and polishing processes are the dominant technologies used to meet surface finish requirements in this natural material. The experiments are aimed at the determination of the normal component of the cutting force and of the grain traces in microcutting with a single diamond grain. The investigations carried out make provisions for establishing critical grain penetration and cutting depths and allow the prediction of the normal cutting force component as a function of grain penetration speed and depth.

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The paper contains an experimental study of microcutting intended to help the optimization of the grinding process of the oxide ceramic CM332 (99.5% Al2O3) grinding. The need for investigating the mechanisms occurring between the abrasive material and the ceramic is imposed by the fact that grinding is the dominant technology used to achieve the required quality of the workpiece surface finish. The microcutting process was performed with a single diamond cone-shaped grain of tip radius of 0.2 mm at varying depths of cut. The investigations were carried out to determine the normal and tangential cutting forces, the critical penetration depth and the specific grinding energy as a function of the grain penetration speed and depth. The critical grain penetration depth separating ductile flow from brittle fracture falls within the 4–6 μm range. The values of the critical penetration depth are also consistent with the results of changes in the cutting forces and the specific grinding energy. The chip formation mechanism is associated with the presence of median/radial and lateral cracks, ductile flow, chipping along the groove, and crushing beneath the diamond grain, all this affecting the quality of the ceramic's machined surface.

The paper presents PCBN-Ciborit cutting tools life and wear test results. The effects of the machining regime when turning amorphous-crystalline Fe 80 B 20 and Fe 79 Cr 16 B 5 coating systems applied to conventional workpiece materials were assessed. It has been shown that the observed tool wear mechanisms are complex in their character and are dominated by abrasive-mechanical, adhesive and chemical effects in the cutting zone. Under changing turning conditions tool life is affected by the structural-phase composition and by the non-homogeneous structure of the coating. Specifically, when turning gas-flame coatings deposited with a Fe 80 B 20 electrode and electro-arc coatings with a Fe 79 Cr 16 B 5 electrode the lowest wear and the highest tool life was achieved at cutting speeds of v = 1.1 to 1.2 m/s and a back rake angle of γ =-10º. It has been demonstrated that a change of the back rake angle from γ = 0 to-10º does not have a great effect on tool life contrary to the case with γ =-20º.