... metal bits and steel-shot could be selected to different layers. (3)The drilling depth which is 100m or 180m must ... up no load max3 m/s Spindle speed as lowering down no load max4 m/s Feeding pressure max.23 KN ... KN Drum speed121,76,36 r/min Drum circumferential velocity (two layers)1.05, 0, 66, 0, 31 m/s Drum dia140 ...