... 3.Water Hole: 2 4.Body: Normal Taper Drill Bits Rock The Advantages Of Taper Drill Bits Rock1. Higher Quality2. With Strict Quality Control3 ... rock hole within diameter of 50mm. The drill tools are used in metallurgy mine, geological exploration, water conservancy construction, electricity, traffic, ... .8,6,7,11,12The diameter for taper:15,19,22,24,25(mm) Drill TypeBit diamater (D)TaperWhter hole(d ...