INFLUENCE OF CUTTING MODES ON WEAR RESISTANCE OF CUTTERS AND ACCURACY OF FINE BORING OF STEELS

This paper is devoted to experimental study of fine boring of steels, which improves performance and parameters of processing accuracy. The conditions that ensure high wear resistance of cutting blades and improvement of accuracy parameters and processing quality were determined by changing cutting conditions and special geometry of carbide cutters with chip-curving chamfers. In the experiments, single-cutter boring was used, as well as double-cutter according to the feed division method. On the basis of the method of planning an experiment in the presence of a large number of variable input parameters, rational values of speed, feed, depth of cut, as well as parameters of roughness, taper and deviations from the roundness of the machined holes are established. The effect of fine boring modes on wear and tool life of cutting edges has been clarified. The influence of the compliance of cantilever boring bars on the level of oscillation of the cutter was also studied. It was found that intense vibrations occur for boring bars of small diameter 0.1 mm, resulting in intensive wear of the cutters. In preliminary experiments, it was found that boring of soft parts (type 20X and steel 30) is significantly different from machining harder steels and requires the use of other cutting conditions. Although the groups of structural carbon, high-quality and alloy steels may differ insignificantly in terms of processing conditions and the results achieved in the process of fine boring, however, for processing steels with special properties, a distinctive feature arises, namely increase in the level of vibrations with increasing cutting speed within the range usually used for other steels. This paper shows results of an experimental study of the process of thin boring of 35L steel with cutters made of TЗ0K4 hard alloy and chip-curving chamfers along the cutting blades.