A drawing of a shaft specifies to turn the outer diameter to 20h6. What is the maximum permissible size of the shaft in mm

55) Datum is required to measure

56) You have to file an aluminium block to smooth finish. Which one of the following cut of file is most suitable

57) Least count of engineer's steel rule is

58) The outer dia of the blank for cutting external thread of M8 x 1 is approximately