Deep hole drill with positive taper and principle for elimination of drill deviation using cutting fluid

Abstract

Prevention of deviation during deep hole drilling is a universal problem. This paper proposes a principle for elimination or reduction of deep hole drill deviation using cutting fluid. The principle is based on hydraulic locking, which is caused by fluid pressure. We developed a deep hole drill with a positive taper. The proposed deep hole drill comprises a tip, a shank and a taper, or a self-centering part (SCP) with a taper; existing drills, in contrast, do not contain tapers. On the proposed drill, the taper or SCP is set between and attached to both the tip and the shank. When the taper deviates during deep hole machining, a lateral force F is created in the radial direction. F will eliminate or reduce the deviation or eccentricity value automatically, ensuring that the taper and the deep hole maintain the same axis, keep the taper, tip, and shank moving along the axis of the machined deep hole, and improve the deep hole quality. A formula for calculating the lateral force is provided and is then proven. Experiments showed that the deep hole straightness quality was higher when drilled using the deep hole drill with the taper. We conclude that the deep hole straightness improvement results from the lateral force F produced by the taper. F is found to vary with taper length and diameter, and the taper design is introduced. The proposed technique is easy to implement with low cost and is promising for widespread application.