64) The endurance limit for a mirror polished material will be __________ as compared to unpolished material.

65) A sliding bearing which operates without any lubricant present, is called

66) The material used for brake lining should have __________ coefficient of friction.

67) Screws jacks have multiple threads.

68) In an ordinary bolt, the effect of the impulsive loads applied axially is concentrated on the cross-sectional area at the root of the threads.