Research on the mechanism of single-tooth BTA deep hole processing under the condition of a weakly rigid slender drill rod

The BTA deep hole system comprising the workpiece, tool, and drill rod functions as a unified and organic whole with interrelated dynamic characteristics. Despite its significance, this interplay is often overlooked in current research on BTA deep-hole drilling mechanisms. Therefore, this paper accounts for the elastic deformation of the slender drill rod and the nonlinear interactions between the tool and the workpiece. By employing the fundamental principles of nonlinear dynamics and the finite element method, a longitudinal–transverse-torsional vibration FEM dynamic model of the BTA tool is developed specifically under the condition of the weakly rigid slender drill rod. By integrating the FEM model with drilling experiments, the mechanisms of single-tooth BTA deep-hole machining are studied. The research findings reveal that the contact pressure of the first guide bar is greater than that of the second, and it is also more sensitive to the feed rate, which can result in more severe wear compared to the second guide bar. Increasing the feed rate will increase the lateral displacement of the BTA tool. A smaller feed rate can be chosen to improve the machining quality. The degree of chip curl gradually increases from the inner to the outer edge, making the chips less prone to breaking. It is recommended to increase the rake angle or flank angle in the design of the middle and outer cutting edges to facilitate chip breaking. The research provides feasible strategies for optimizing tool structure and process parameters, as well as a foundation for vibration control.