40) "Work piece is to be turned on a lathe machin." What is the spindle speed (RPM) to be set, if the cutting speed is 60 m/min and the diameter of the work is 30 mm?

41) A grinding wheel is marked "51C60M6S23". Here the S indicates

42) Which one of the following time taken is correct to turn a job on lathe machine having length 350 mm, feed 0.05 mm/rev, spindle speed 350 RPM and number of cuts is 1?

43) Standard wheel marking is given as 'A16P5V" on grinding wheel. Where 'A' represents

44) Which of the following formulae is correct to find the helix angle of screw thread?