1.PDC coal mining tools 2.ore mining, many type 3.good price,high quality 4.professional manufacurer 5.export many ... (6, 7, 11, 12 degree taper).Bit diameter: 28mm-57mm.3. Extension drilling toolsButton bit, face design: Flat face, Drop centre ... .8. Blast furnace tap hole drill tools. (Rod, Cross bits, button bits and X-type bits etc). PDC coal mining tools