Accuracy of Thread Profile Depends on the Lathe Tool Angle of Inclination. Theoretical Investigation

Abstract

Abstract Among threaded connections of large sizes, tapered thread pipe connections are especially often used, which are a very important part of drill strings. The efficiency of the drill strings largely depends on the accuracy of the tool-joint tapered thread. The production of such joints is implemented on lathes, with the help of tools that have a carbid insert. To ensure high performance, such inserts are recommended to be installed not parallel to the axis of the thread, but at the lead angle of thread. However, the profile of the insert itself is equal to the profile of the thread, and therefore it is important to have a theoretical predictive calculation of the probable influence of the angular setting of the carbide insert on the accuracy of the thread. Based on a detailed consideration of the geometry of the mutual placement of the plate and the tapered thread and the kinematic features of the process, an algorithm for predictive calculation of the accuracy of the thread is created. The result shows that only one of the parameters of the cutting edge really depends on the angle of inclination of the cutting edge - it is its profile. The deviation can reach 7% of the tolerance on the semi-profile angle.