Development of a chip breaker for external threading of modified ABNT 4133 steel

The oil and gas market has increased during the last years due to a higher demand for energy resources. Pre-salt areas require deeper wells, pipes more resistant to internal and external pressures, high temperatures and also to corrosive environment. This scenario requested the development of new steel grades and new designs for threaded connections, thus increasing chips formation and the difficulty to break them. It brought issues for conveyors maintenance and safety risks for machine operators. Despite this period of intensive development in the oil and gas market, only a few studies for chip breakers specifically designed for this application have been conducted. In general, pipe manufacturers buy chip breakers from off-the-shelf, i. e. chip breakers that were not designed for this segment, thus not providing optimum results. This work is concerned with the development of a chip breaker, based on the rake face wear of the threading tool. The approach is to change the distance of the chip breaker from the cutting edge. Four developed chip breakers and a commercial one were tested. During the tests, cutting speed, depth of cut and allowance were varied in order to assess their impact on chip breaking effectiveness and work piece quality. The results show that the closer the chip breaker to the cutting edge, the more efficient they were in breaking the chips, the allowance had not any influence and depth of cut was the most influent factor thread quality. Finally, it was not possible to identify any variation in power consumption of the main spindle when the chip breaker was changed

Chip breaker; threading; oil and gas