... 108mm/25mm*159mm3) length: 0.4m-10m Different rock formations and rock drills require different taper angles. When drilling with high ... used on modern drill rigs. For low impact rock drills and softer rock formations, a narrow taper angle of seven degrees ... small hole drilling, equipped with small power rock drills, like air leg rock drills, hand held rock drills, etc. It can reduces the expense of ...