37) The thread which is combination of triangular and the square thread is

38) Caulking or Fullering is done on rivet joint to

39) The following is one of the taper key

40) When the solid is inclined to HP and VP, how many principal positions are required to obtain orthographic view of solid?

41) For spur gear of pressure angle 20 degree module as 100 mm and having 36 teeth will be having and addendum circle Da as