Edge finishing and deburring of back surfaces of microholes using micro-cutting tools

The edge finishing and deburring of the back surfaces of micro-through holes, such as those with a diameter smaller than 1 mm, from the front surfaces by cutting are difficult and in some cases impossible with currently available tools. We have therefore fabricated micro-cutting tools by electrical discharge machining and used them for processing the back surfaces of microholes using helical tool feeding with the assistance of ultrasonic oscillation. As a result, a hole drilled using a 0.15-mm-diameter drill in a 0.2-mm-thick plate was successfully deburred and edge-finished. This is the hole with the smallest diameter whose back surface was processed from the front surface by cutting, to the best of our knowledge. The effects of ultrasonic oscillation, namely, cutting force is reduced and the generation of secondary burrs is restrained, were also observed in this study. Moreover, cutting force was further reduced with an improved geometry of the toolʹs cutting part.