It has been already proved that hard turning is capable technology in cutting of hardened steels however, there are few results regarding to bore manufacturing. The replace ability of hard turning against grinding must be defined in high precision bores when the workpiece has different geometry (e.g. bore diameter, length to diameter ratio). As tolerances given for a workpiece are getting stricter, the transition range between hard turning and grinding must be determined. In some cases, it can be also worthy to utilize the advantages of these two processes to create a powerful combined technology. A "set of rules" was developed to assist the selection of proper process at process planning. The research work focussed on manufacturing of high precision bores, like gears and injection nozzles in the field of the automotive industry. The aim of this work was to select the proper process and process conditions in manufacturing high precision bores. The limit of hard turning was studied, and the transition range between hard turning and grinding was defined.