Climb Up, Slide Down
So far, the screws you have read about spin round and round. But some screws don’t move at all. Yet they make jobs easier―and more fun!
Have you ever seen a spiral staircase? It comes in handy when there is not a lot of space to spread out a flights of stairs. A spiral staircase is shaped like a screw. Now, what if you replace the stairs with a smooth surface? You have a spiral slide!
A spiral staircase is nothing more than a big screw!
Move It Along
Screws are amazing machines. We use them to hold things together, dig holes big and small, and save space. But these simple machines do another very important job. They move things.
Think about the drill bit spinning into the wood. As the bit drills the hole, wood shavings and sawdust come out of the hole. These are the tiny pieces of wood that the bit removes. It’s like digging a hole with a shovel and tossing the soil around the opening. But how does a screw, like a drill bit, move things this way?
As the drill bit turns and carves out the wood, the grooves between the threads carry the removed pieces of wood up along the bit.
This idea that a screw could be used to move things led to an important invention more than 2,000 years ago. A mathematician from ancient Greece figured out how to use a screw to lift water from a river to irrigate crops. His name was Archimedes (sounds like ahr‑kuh-MEE-deez), and the invention is called an Archimedes’ screw. Here’s how it worked:
A large screw was fitted inside a tube. One end of the tube was placed in a river. A worker turned a crank at the other end. The turning threads of the screw pushed the water up the tube and dumped it out at the other end. From there, it flowed along ditches to fields. Archimedes’ invention is still used today. A screw is a simple machine, but our uses for it are anything but simple!