A STUDY ON THE TOOL EIGENPROPERTIES OF A BTA DEEP HOLE DRILL - THEORY AND EXPERIMENTS

Abstract

The dynamics of a tool shaft are usually simplified to that of a second order lumped mass system for cutting process. This approach does not apply for deep hole drilling because of its extraordinary shaft length. This paper established the equations for lateral and longitudinal shaft motion of a BTA drill based on the Euler beam theory. Free-free boundary conditions are used in order to solve the eigenproperties of the shaft. Experiments to determine properties of the shaft, the shaft with internal static fluid and the shaft with cutting head were performed. The agreements between the theoretical and experimental natural frequencies and mode shapes confirmed the proposed equations. Some effects, including those of static fluid and the cutting head were clarified. This study has shown the existence and importance of the BTA tool shaft dynamics which were often overlooked or oversimplified in the past.