Nasmyth, NAY smihth, James (1808-1890), a Scottish engineer, invented the steam hammer in 1839. His steam hammer was able to forge large parts for steamships and railroads. He also developed the self-acting principle in machine-tool design, by which a mechanically held tool moves along a track and works on a stationary workpiece. Using this principle, Nasmyth invented a planing mill and a nut-shaping machine.