Machine Design
Basic shaft is one

Whose upper deviation is zero
Does not exist
Whose lower deviation is zero
Whose lower as well as upper deviations are zero

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Machine Design
Machine screws are

Similar to small size tap bolts except that a greater variety of shapes of heads are available
Used to prevent relative motion between two parts
Similar to stud
Slotted for a screw driver and generally used with a nut

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