EXERIMENTAL ESTIMATION OF HARD TURNING CONTACT CHARACTERISTICS

Abstract

When processing hardened steel with a PcBN cutting tool in conditions close to orthogonal cutting, the cutting forces are determined depending on the amount of feed and cutting speed. The value of contact stresses, friction coefficient and the length of contact of the chip with the front surface of the cutter for a cutting speed of 100 m/min were determined, and the sections of the chip were obtained, which demonstrate the morphology of the chip. It was experimentally established that when processing hardened bearing steel, the magnitude of the tangential and radial components of the cutting force acting on the front surface of the tool at a feed of 0.05 mm/rev and a cutting speed of 100 m/min is 125 N/mm and 42 N/mm, respectively. The average coefficient of friction is 0.33. It is shown that to measure the contact length of the chip with the front surface of the cutter, it is advisable to use thin metal PVD coatings with a thickness of ~ 0.1 μm, which allows to increase the accuracy of determining this parameter. Chip samples obtained in the investigated range of processing conditions indicate a segmental type of chip formation. Chip thickness measurements obtained at a feed of 0.05 mm/rev and a cutting speed of 100 m/min range from 40 to 80 µm in thickness.