The Screw as a Simple Machine for Middle School Science

May 12

4 min read

A screw is a simple machine that helps hold things together, lift objects, or move materials. At first glance, it may just look like a metal pin with threads wrapped around it, but it’s actually one of the six classical simple machines that help people do work with less effort.

How a Screw Works

A screw is made of an inclined plane wrapped around a central shaft. The ridges, called threads, spiral around the shaft in a regular pattern. When you turn a screw, the threads pull the screw into a material or move objects along the threads, depending on the type of screw and how it's used.

This twisting motion allows the screw to turn a rotational force (called torque) into a straight-line force. That’s why screws can hold objects tightly together or lift things with precision.

Why It’s a Simple Machine

The screw is a simple machine because it changes how force is applied. Instead of pushing something straight in, you can apply a turning motion, which requires less force spread over a longer distance. Just like the inclined plane it’s based on, the screw makes difficult jobs easier by reducing the effort needed.

The History of the Screw

One of the most famous early uses of the screw as a simple machine is the Archimedes’ screw. This device was invented around 250 BCE by the ancient Greek scientist and engineer Archimedes. It was designed not for fastening objects, but for lifting water from a lower level to a higher one.

The Archimedes’ screw consists of a spiral-shaped surface (like a screw thread) inside a hollow tube. As the tube turns, usually by hand, water trapped between the threads moves up the spiral and out the top. This clever design allowed farmers and builders in ancient times to irrigate crops, drain water, or fill containers with much less effort than carrying water by hand.

Although Archimedes is given credit for this invention, some historians believe similar devices may have been used in Egypt before his time. Still, Archimedes was the first to study and describe it in detail.

The Archimedes’ screw became widely used in the Greek and Roman worlds and continued to be important through the Middle Ages and into modern times. Today, updated versions of the Archimedes’ screw are still used in places like wastewater treatment plants, hydroelectric dams, and even in grain elevators to move materials.

Later, in ancient Rome and during the Middle Ages, screws began to be used in tools like wine presses and oil presses. Metal screws for fastening things didn’t become common until the 15th century, when better tools were developed for making the threads more precisely.

Screws in History

During the Middle Ages (roughly 500 to 1500 CE), the screw became an important tool in two major inventions: clocks and presses. These devices helped people keep time and share information—two things that changed everyday life in powerful ways.

In mechanical clocks, which were first developed in Europe in the late 1200s, screws were used to hold tiny parts together and allow precise adjustments. These early clocks had many gears and moving parts, and the screw helped keep everything tightly in place. Without the screw, these complex machines would not have worked correctly. The use of screws allowed clockmakers to build better and more accurate timekeeping devices, helping people measure hours and minutes for the first time.

Screws were also essential in building presses, especially the wine press and later the printing press. In a wine press, a large wooden screw was turned to slowly lower a heavy beam, which crushed grapes and squeezed out the juice. This same idea was later used in the printing press, invented by Johannes Gutenberg in the 1400s. The press used a screw to press inked letters firmly onto paper. This invention made books easier and faster to produce, helping spread knowledge across Europe.

The Industrial Revolution, which began in the late 1700s and continued through the 1800s, was a time of major change in technology, manufacturing, and transportation. During this period, screws became much more common and important because new machines made it easier to produce them quickly and accurately.

One major use of screws during the Industrial Revolution was in machinery and engines. As factories began using steam engines and other machines, screws were used to hold parts together, adjust moving pieces, and make repairs easier. Screws helped make machines more reliable and easier to build and maintain.

Screws were also essential in the textile industry, which was one of the first industries to grow rapidly during the Industrial Revolution. Textile machines like spinning frames and looms used screws to control tension, hold frames together, and adjust parts as cloth was made. These machines allowed factories to produce cloth much faster than ever before.

Another important use of screws was in the railroad industry. As trains and railways spread across Europe and North America, screws were used to secure metal parts, connect rail lines, and build locomotives. The strength and reliability of screws made them ideal for heavy-duty use in transportation.

Finally, screws became more common in everyday items like furniture, tools, and household devices. Thanks to machines that could mass-produce screws, people could now buy items that were easier to assemble, fix, or improve.

How We Use Screws Today

Screws are everywhere in modern life. Some common uses include:

Construction: Holding together wood, metal, and plastic parts in buildings, furniture, and tools.
Machines and electronics: Securing tiny components inside computers, phones, and engines.
Jars and lids: The threads on bottle caps and containers are a form of screw.
Lifting devices: Some jacks and presses still use screw mechanisms to lift or compress objects.
Medicine: Special medical screws are used to help repair bones and joints.

Whether you’re putting together a chair or turning on a faucet, chances are you’re using a screw without even realizing it.

The screw may seem small and simple, but it’s a powerful tool. By turning rotation into force, it helps us build, fix, and move things more easily. Like all simple machines, the screw is proof that smart design can turn a hard job into an easier one—something humans have been doing for centuries.