Chainsaw

A **chainsaw** is a tool that cuts wood with a **circular chain** that is driven by a **motor** and made up of many connected **sharp metal teeth**. A chainsaw has two main parts: a **saw blade** built into a chain, wrapped around a long metal **guide bar**, and a **one-cylinder gasoline engine**. The chain is running around sprockets only with about thirty sharp teeth made from steel.



Inside the engine, as the piston moves in and out of the cylinder, it pushes a connecting rod that turns a crankshaft. The **crankshaft turns gears** that are connected to one of the sprockets on which the chain is mounted ‒ and the chain spins around.



The prototype of the chainsaw familiar today in the timber industry was pioneered in the late **18th century** by two Scottish doctors. They used it for an excision of a diseased bone.



Chainsaw use can cause some serious injures. A common accident arises from a kickback, when a chain tooth at the tip of the guide bar catches on wood without cutting through it. This throws the bar (with its moving chain) in an upward arc toward the operator which can cause serious injury or even death.