| 摘要 |
An object of the present invention is to provide a drill bit which is simple in design, high in rigidity, and superior in durability and whose drilling function is in no way inferior to that of conventional drilling bits. To this end, in a drill bit comprising a cutting blade tip 2 which is united tightly to a tip end of a bit body 1 and a plurality of cutting blade portions 2a, 2b and 2c which are formed around the cutting blade tip 2, a flat surface portion 3 is formed in a side surface of the drill bit from between adjacent cutting blade portions to a base portion of the bit body 1 so that the bit body 1 is formed into a straight configuration having an approximately polygonal cross section. <IMAGE> |
