Drilling of microholes down to 10 μm in diameter using ultrasonic grinding

Drilling by grinding is useful for fabricating holes in hard and brittle materials with high dimensional accuracy and low machining cost. However, its application to microholes has been limited to those with a diameter on the submillimeter order. The drilling of microholes less than 0.1 mm in diameter by grinding was therefore attempted on crown glass. Cemented tungsten carbide micropins were fabricated by electrical discharge machining and used as micro-grinding tools. They can be employed because the convex parts of discharge craters formed on the tool surfaces serve as cutting edges of abrasive grains of grinding wheels. In order to reduce grinding force and thus prevent tool breakage, ultrasonic grinding was employed with the workpieces ultrasonically oscillated. As a result, microholes down to 10 μm in diameter were successfully drilled. They are the smallest-diameter holes drilled by grinding, to the best of our knowledge. The effect of helical feeding, in which the tool not only rotates around its axis but also moves in planetary motion, on drilling properties was also investigated.