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The main problems during cutting with circular saw blade are inaccurate cut, low quality of surface, high level of noise. These adverse eff ects are related to oscillation of circular saw blade. This oscillation cause adverse eff ects not only on workpiece but also on tool. In some case the circular saw blade reaches the value of critical rotational speed which leads to its instability and cause the oscillation of blade which may leads to destruction of tool. So the reduction of the amplitude of oscillation is essential for removing the adverse eff ects. This paper deals about infl uence of shapes of teeth as a type of modifi cation that has positive eff ect oncritical rotational speed of circular saw blade. The parameters of studied models of circular saw blade were 42 number of teeth and the height of teeth with slice from sintered carbide was 14 mm. The variable parameter was the ratio between surface of teeth and surface of teeth gap. In this study was used computer so ware Creo Parametric 1.0 for obtaining natural frequencies of studied models. This so ware uses in analysis fi nite element method (FEM). There were done some steps to idealize the models. For calculating static and dynamics natural frequencies of modelswere used modal analysis. The critical rotational speed was calculated from obtained results by Creo Parametric 1.0 and compared on 5 models of tool.

The cutting power value, the surface quality of the machined surfaces, and the cutting edge wear were determined in the planar milling of oak wood (Quercus robur L.). The experimental tool was a milling head with two interchangeable blades. The basic material of the three milling cutters was HS 18-0-2-5 high-speed steel (ISO 4957 2018). Two milling blades were treated with different coatings: a multilayer AlTiCrN coating of thickness 1 μm to 4 μm (knife B) and a multilayer MoC coating of thickness 1 μm (knife C). Parameters for the experiment were as follows: tool angular geometry: α = 30°, β = 45°, γ = 15°, and δ = 75°; spindle speed: 3000 min-1, 4000 min-1, and 5000 min-1; feed rate: 6 m/min, 8 m/min, 10 m/min, 12 m/min, and 14 m/min; cutting depth: 1 mm and 2 mm. The results showed that the cutting power for face milling increased with milling length for all three blades. The greatest power was measured at milling using the knife C (mean value of 209.3 W). The wedge wear parameter WBW increased with milling length; knife C reached the greatest value (WBW = 54.0 μm at length of 270 m). The surface quality parameter (Ra) of the machined surfaces was almost unchanged with increasing milling length beyond 90 m for all knives.

Cutting, as the most widely used machining process, is applied in both primary and secondary wood processing. Optimum cutting conditions that result in the high quality of the machined surface and low energy consumption are crucial for wood processing. The effects of the feed speed, cutting speed and average chip thickness on the energy consumption and surface temperature of a circular saw blade during the cutting process of two types of plywood with a thickness of h = 14 mm is described in this paper. In experimental measurements, two circular saw blades with cutting tungsten carbide inserts for wood were used as tools. One circular saw blade was standard, and was not surface treated (CSB1), and second circular saw blade (CSB2) differed by the powder coating surface and the length of the cutting edge. In the experiment, the energy consumption and the surface temperature of the circular saw blade was measured in order to find the optimal cutting conditions for the most energy-efficient cutting process. The results show that the cutting power and the surface temperature of the circular saw blade increased when the feed speed increased. The investigated values of the surface-treated circular saw blade were lower compared to the values of the standard circular saw blade. When comparing the lightweight plywood with the classic plywood, experimentally obtained cutting power values of the circular saw were made 19% lower on average by using the circular saw blade CSB1. When using the CSB2 circular saw blade, these values of the cutting power of the circular saw were 22% lower on average. The surface temperature of the circular saw blade is the highest on the outer edge (tooth root area 31.7 °C) and decreases towards the center of the circular saw blade. There must be a reasonable compromise between machine productivity and energy consumption.

• In most cases high cutting speed is used when cutting wood by circular saw. This results in oscillat-