Drilling of Microholes Using Diamond Grinding Tools

The drilling of microholes in hard and brittle materials by ultrasonic grinding was carried out using polycrystalline diamond (PCD) micropins fabricated by electrical discharge machining. They can be employed as micro-grinding tools because the convex parts of discharge craters formed on the tool surface can serve as cutting edges of abrasive grains in grinding wheels. In the drilling of crown glass, the increase in the grinding force and the generation of cracks and chippings at hole edges were suppressed owing to the high wear resistance of PCD. Under suitable conditions, drilling was also successfully performed in silicon, which is apt to exhibit cracks and chippings at hole edges.