The deep hole boring tool

A great number of parts which are used in in machine building industry contain deep holes. Its production requires a special tool with a large length-to-diameter ratio boring bar. The boring bar significantly changes its length during lengthy blanks processing. Therefore, natural frequency of the tool changes too. Deep hole boring is inevitably accompanied by the appearance of the resonance, when the forced oscillation frequency, dependent on the operating mode, multiples the natural oscillation frequency of the tool. There is another phenomenon accompanying the deep holes’ machining, called chatter. This kind of self-excited vibration can also lead to resonance. It causes various working errors to appear, the one hardest to reduce being the wall thickness variation, which is presented due to the tool axis deviation in relation to the axis of the hole. Authors suggested a boring bar equipped with gyroscopic stabilizer. It contains a frame mounted on the body of stabilizer by the means of cardan suspension, which provides two degrees of freedom for the gyroscope. The third degree of freedom is offered by the boring bars’ body. Gyroscopic stabilizer mounted inside the boring bar and behind the tool. Thus, when the boring bar starts to bend the frame simultaneously starts to swing and it achieves the lateral vibration suppression. The paper covers the proposed method of deep holes manufacturing. A structure of gyroscopic stabilizer for boring bars with a large length-to-diameter ratio is presented. The experimental stand for the study of the process of damping by the proposed method is described. Ninefold reduction of the amplitude of the resonant vibrations is achieved in the forced oscillations frequency range of 152...1100 rad/s for following values of the natural oscillations frequency of the tool model: rad/s, rad/s, rad/s, rad/s. It is established, that achieving lower values of the vibrations amplitude requires the tool to be maintained in a resonant or near-resonant state. It allows minimizing tool axis deviation and its consequences, which reduce the accuracy of the deep hole machining.

deep hole boring tool, gyroscopic stabilizer of the tool