Influence of chip breaker and helix angle on cutting efforts in the internal threading process

Abstract

Tapping process is an important machining process to produce internal threads with accuracy, quickness, and low costs. The constant study of the tapping process is necessary due to the value added to the product when the tapping step occurs. The threading operation is the last manufacturing process used in a component having one or more threaded regions. Thus, because several manufacturing processes were used before the threading process, the value added to the product is significant, and the loss of this component represents severe financial damages to the industrial sector. This work analysed the tapping process with two types of taps considering the torque and thrust force as the main response. Workpieces of SAE 1020 steel with dimensions of 122 × 22 × 20 mm were used due to its broad application in industry and mainly because this steel presents excellent machinability. The torque and thrust forces were monitored using a piezoelectric dynamometer with an acquisition rate of 600 Hz. Taps M8 with the pitch of 1.25 mm with and without chip breaker were applied in experimental tests. The initial hole was the same for all experiments with the value of 6.8 mm. The results demonstrated that torque and thrust force had a different behaviour increasing or decreasing with the change of cutting speed, type of coating, and the use or not of chip breaker. Thus, it can be concluded that taps with higher helix angle, without chip breaker, and coated were the best option for tapping in threaded blind holes.