39) Saw tooth thread is a form of

40) A hole is to be reamed on Mild Steel with a 8mm reamer. If the u ndersize is 0.2mm and oversize is 0.05mm, diameter of the drill for drilling the hole before reaming, ideally should be

41) Predominant alloying element in stainless steel is

42) The carbon content is high carbon steel is

43) Density of aluminium is