For cutting soft materials, the most suitable pitch of the hacksaw blade is

39) Clogging of metal chips in a file is known as

40) Which of the following file is commonly used for die sinking, engraving and in silversmith's work?

41) Calculate the number of cutting stroke per minute in a shaping machine having a speed ratio of 2:3. (cutting speed = 20 m/min, length of stroke = 180mm)

42) In a slotting work, the length of the stroke is 300mm, number of double stroke per minute is 40, and the ratio of return time to cutting time is 2:3, find the cutting speed.