11. A hole of 12mm and 25 mm depth is to be drilled using an HSS drill for a medium carbon steel. For average metal cutting conditions, determine: (i) suitable speeds (rpm) and feeds (mmrev); (ii) the time to machine the hole. #80 18. Using the data in Table Q6.18 and the drawing in Fig. Q6.18, determine suitable speeds (rev min) and feeds (mm rev) and the total machin- ing time for all operations listed. The raw material billet is 085x250mm and the machining allowance to be used is 5 mm. Process parameters TABLE Q6.18 Operations and cutting conditions Operation description Face end Tooling description Cutting condition HSS turning tool Turn 80mm x 160mm HSS turning tool Turn 70mm x 100mm HSS turning tool Turn 60 x 60 mm Parting off HSS turning tool Finish in one pass One roughing cut, one finishing cut of 0.4 mm One roughing cut, one finishing cut of 0.4 mm One roughing cut, one finishing cut of 0.4 mm HSS parting off tool Finish in one pass P8 160 100 60 P7 P6 P5 P3 P4 P1 P2 #70 060 Figure Q6.18 Brass component 10 90 #50 3. A 40mm HSS face mill is being used to machine grey cast iron. Det- ermine a suitable speed in revmin" for average metal cutting conditions.