WHAT DOES A SCREW DO?

WHAT DOES A SCREW DO

Screws do one basic thing. They convert a force that goes around and around into a force that goes up and down. This force can be used to push against an object. The up and downforce generated by a screw can also be used to hold things together. Screws can thread into a metal nut and the up and down force holds the two together. One big advantage of screws used as fasteners is that they can be removed and reinserted many times without losing their effectiveness. They have greater holding power than nails and can be easily disassembled and reused. Screws can also be used to lift things. A device called an auger is used for lifting or pumping water or another liquid. As the screw turns in the water, the water is lifted. This is also how a concrete mixer (truck) unloads its load of concrete.

HOW DOES IT GET POWER?

A screw is powered by the movement of the screwdriver. It converts this rotational force (called torque) into up and downforce. A screw's power depends on how close together the threads are and how far away from the center of the screw force is applied. You can get more power by making the threads closer together. If the threads are close together, then with each turn of the screw it travels a shorter distance but exerts more force. With tighter threads, you have to turn the screw more times before it is tight. You can also get more power by using an object that allows you to apply force farther from the center of the screw. This is why it's easier to turn a screw or bolt with a long wrench than a shorter one. But there is a downside to using a longer wrench. With a longer wrench, you have to move the wrench farther in order to turn the screw the same distance.

Certain screws may have different shapes, sizes, etc. to suit different needs. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the internal thread formed into it. Other screw threads are designed to cut a helical groove in a softer material as the screw is inserted. Most screws are tightened by clockwise rotation, which is termed a right-hand thread. Screws with left-hand threads are used in exceptional cases. For example, when the screw will be subject to anticlockwise forces (which would work to undo a right-hand thread), a left-hand-threaded screw would be an appropriate choice.