30 Diamond Coated Twist Drill Bits Metalworking Tools 20 Diamond Coated Twist Drill Bits. This is a new set of 20 high speed diamond coated twist drill bits. Great for drilling stone, ceramic, glass and other hard non-metallic materials. These have straight shanks and are made of high quality steel. These bits are sizes #61 to #80 10 Diamond Coated Twist Drill Bits. This is a new set of 10 high speed diamond coated twist drill bits. Great for drilling stone, ceramic, glass and other hard non-metallic materials. These have 1/8" (3 mm) shanks. We work hard to update our descriptions and pictures of our merchandise. As part of a process of ongoing innovation by our suppliers, newer versions of the item shown may be shipped before we are able to complete an update. As a result there may be a slight variation in color and design.