... , HSS.High Speed Steel Hollow Drilling (of multi-plate drilling, coring drill) Hollow drilling, is a new type of drilling tools, which support Magnetic ... Drill Block, the large steel components can be anywhere drilling, efficiency is Twist Drill-10 times, can be controlled in ... the 0-0.05 mm tolerance, but also a reaming, drilling half hole, ramps, and other unique features of faces.Widely ...