The development of computer aided resources in automation of generation of manufacturing routings and operations is being mainly accomplished through the search of similarities between existent ones, resulting standard process routings that are grouped by analysis of similarities between parts or routings. This article proposes the development of manufacturing routings and operations detailment using a methodology which steps will define the initial, intermediate and final operations, starting from the rough piece and going up to the final specifications, that must have binunivocal relationship with the part design specifications. Each step will use the so called rules of precedence to link and chain the routing operations. The rules of precedence order and prioritize the knowledge of various manufacturing processes, taking in account the theories of machining, forging, assembly,and heat treatments; also, utilizes the theories of accumulation of tolerances and process capabilities, between others. It is also reinforced the availability of manufacturing databases related to process tolerances, deviations of machine tool- cutting tool- fixturing devices - workpiece,and process capabilities. The statement and application of rules of precedence, linking and joining manufacturing concepts in a logical and structured way, and their application in the methodology steps will make viable the utilization of structured knowledge instead of tacit one currently available in the manufacturing engineering departments, in the generation of manufacturing routing and operations. Consequently, the development of Computer Aided in Process Planning will be facilitated, due to the structured knowledge applied with this methodology.