Circular saw

Invented in England in 1780, the circular saw is a metal disc (or blade) with saw teeth on the edge as well as the machine that causes the disk to spin. It is a tool for cutting wood or other materials and may be hand-held or table-mounted. Today they are usually powered by electricity, but large ones in "saw mills" (where whole trees are sawed into lumber) were traditionally powered by water turning a large paddlewheel.