Center drill is used for parts such as side surface of the shaft center hole processing. The product is cutting light, good chip. There are two types of center diamond: A type: non-care center cone drill, B-: with care center cone drill, machining diameter d = 1 ~ 10mm center hole, usually without a care center cone drill ( Type A); process is longer, high precision parts, in order to avoid the 60-centering cone is damaged, the general center of the cone with a cone care (B)