Material removal processes are operations that remove excess material from the starting workpiece so that the resulting shape is the desired geometry. The most important processes in this category are machining operations such as turning, drilling, and milling. These cutting operations are most commonly applied to solid metals, performed using cutting tools that are harder and stronger than the work metal. Grinding is another common process in this category. Other material removal processes are known as nontraditional processes because they use lasers, electron beams, chemical erosion, electric discharge, and electrochemical energy to remove material rather than cutting or grinding tools.