Accuracy of machining internal threads with a combined tool

The article considers the operation of a special tool designed at the BMSTU for CNC machining of complex shape threaded holes. The tool combines the functions of a drill and a thread mill. The dependence of the kinematics and such machining parameters as thread diameter and pitch, and a toolhole diameter ratio on the accuracy of the thread profile has been determined. The kinematics of thread milling results in widening of the thread profile and may introduce an error to the base thread diameter. The results of computer simulation of the thread milling process and the experimental data on threads inaccuracies are presented, a good agreement with the predicted calculations is demonstrated.