6 Simple Machines

The Screw

The screw is an inclined plane that is wrapped around a cylinder or tube.

Examples: drills, jar lids, screw caps, nuts and bolts

The screw transforms rotational force (and rotational motion)
        into linear force (and linear motion).

Screws are almost always tightened by a clockwise motion
        and loosened by a counter-clockwise rotation.
Such a screw is said to have a right-handed thread.

Screws can also be double-threaded, triple-threaded, and so on.
Such screws are called double start, triple start, etc.

Although screws come in many different types, you can be quite sure that the vast majority of screws, nuts, bolts, etc. that you will encounter will have single, right-handed threads.

If we look carefully at the graphic, all 4 of those screws have single, right-handed threads. Did you notice that the threads on the left side side of each screw are lower than the threads on the right side? That is true of all right-handed threads.

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