When difficult-to-machine materials are drilled, chips are produced, and these chips are difficult to control during the drilling process. Due to the limitations of conventional drilling, materials are drilled by ultrasonic-vibration-assisted technology. In this paper, the kinematics of ultrasonic-vibration-assisted drilling are first analyzed and the relevant equations are established. The characteristic thicknesses of chips are then studied, and the drilling paths for different phases and thicknesses of the chips are analyzed. The condition of complete geometric chipbreaking in the ultrasonic-vibration-assisted drilling process is examined, and a regional map of chipbreaking is presented, which in theory allows chips to be controlled. Chips produced in ultrasonic-vibration-assisted drilling with different parameters are compared in a series of experiments. The chipbreaking condition is studied in more detail, and the chips produced by drilling difficult-to-machine materials are effectively controlled. Furthermore, the results of this study show that a reasonable selection of parametric variables in ultrasonic-vibration-assisted drilling results in thin and smooth chips, less tool wear, and superior surface roughness.

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