Affectation of chip formation in single-lip deep hole drilling at small diameters by application of low-frequency vibration support

Abstract

Deep hole drilling processes are relevant for various applications where bore holes with high length-to-diameter-ratios (L/D) and good surface qualities are necessary, carried out mostly at the end of the (machining) process chain. Therefore, the avoidance of tool breakage and the resulting process stability is mandatory. One of the main causes for the failure of single-lip drills in the machining of long-chipping materials is the inadequate chip removal along the tool’s flute. A successful approach to promote active chip breakage is the use of adequate/matching vibration-assistance, either of the tool or the workpiece. The aim of this work is to demonstrate the positive influence of low-frequency and high-amplitude vibration-assistance on the chip formation of age-hardened copper-zirconium, performed by solid carbide single-lip drills with small diameters (down to 0.94 mm, hence a micro-drilling) and L/D-ratios up to 40. The improvements of this deep hole drilling process reflect in significant increases in chip removal rate and thus productivity.