Before the middle of the 18th century WOOD:the main material used in engineering structure LATHES:the machine tools mainly used to cut these material Exceptions:boring of cannon,production of metal screws and small instrument parts.Before the middle of the 18th century WOOD: the main material used in engineering structure LATHES: the machine tools mainly used to cut these material Exceptions: boring of cannon, production of metal screws and small instrument parts