[Sax. hamer."] A well-known tool used for driving nails, beating metals, etc. Hammers are of various sorts, but nearly all consist of an iron head fixed crosswise to a handle of wood. Almost every kind of trade has a hammer of its own. Power hammers are those which are worked by machinery. Among them are forge-hammers, used for hammering into shape heavy masses of red-hot iron; and tilt-hammers, used for lighter work, such as forging bars of steel. The steam forge-hammer was invented by James Nasmyth in 1839.