... ): 400 800 1600 2400 3200 4000 48004) Bit diameter(mm):29,30,31,32,33,34,35,36 ... used by a hand held drill machine in Underground mining and for small hole drilling, equipped with small power ... be used for drilling bore hole diameter from 30mm to 41mm usually. Regarding Integral drill steels,the quality of a ... important to get good drilling performance. International Drill Pipe/mining tools in soil