... and lubricating effect, larger range of drilling depth. 2.New shallow drill . New shallow drills:1.Pre-treated drill with high torsion ... chip pocket, good angle of chip flow, unobstructed chip removal.3. Perfect insert assembling angle, low vibration during cutting, higher ... lubricating effect, larger range of drilling depth.l ZCC.CT New shallow drills with 3/4D, Double helical inner coolant hole