A clockwise (typically abbreviated as CW) motion is one that proceeds in the same direction as a clock's hands: from the top to the right, then down and then to the left, and back up to the top. The opposite sense of rotation or revolution is (in Commonwealth English) anticlockwise (ACW), or (in North American English) counterclockwise (CCW).
Supination. Rotation of the hand or forearm so that the palmar surface is facing upward
Pronation. Rotation of the hand or forearm so that the surface of the palm is facing downward or toward the back
From the anatomical position, with the arms fully extended to the sides of the trunk and the palms facing forward, pronation is the movement of the hands to turn the palms posteriorly. In other words, pronation involves placing the palms into the prone (face-down) position, like someone would do when looking at the backs of their hands....
The reason for the clockwise orientation of most screws and bolts is that supination of the arm, which is used by a right-handed person to turn a screw clockwise, is generally stronger than pronation. Also, it was wise to adopt a single standard version for most screws and bolts – in order to eliminate endless confusion.
Why do screws tighten clockwise?
This is because the biceps muscle - the strongest muscle in our arm - actually has two functions:
1) flexion of the arm and
2) supination (which is the motion used when screwing in a screw clockwise).
Why do clocks go clockwise?
The clock that we use today was originally developed from the sundial, which used the sun to cast a shadow that would tell what the time was. In fact, before clocks had become popular the term wasn’t “clockwise,” it was “sunwise,” because that’s the way the rotation went.