Since recent studies have demonstrated the benefits of hard turning over other abrasive machining processes as a finishing process in terms of surface integrity, a strong need has existed to improve the performance of chucking. It is because the poor repeatability and accuracy in the positioning of chucked workpieces became the major bottleneck in the implementation of finish hard turning for precision mechanical components. However, the understanding of chucking has not been adequate, nor has any systematic method been reported for improving chucking accuracy. In this paper, all the major factors that affect the positioning accuracy and repeatability of a chucked workpiece have been identified by error budgeting and systematic measurements. In addition, the characteristics of these factors, as well as their effect on chucking accuracy, were investigated. From the results, a chucking error map that summarizes the relations between these factors and the positioning error of a chucked workpiece was developed. Then, a series of experiments were carried out, based on the results of the earlier works to test the effectiveness of the error budget. The results demonstrated that the knowledge on these factors was accurate and it could be effectively used to improve the positioning accuracy and repeatability of a range of cylindrical workpieces chucked for machining. It was also shown that hard turning alone, without any extra machining process, could satisfy the same level of concentricity which is currently achieved by finish grinding in the machining of different types of cylindrical workpieces. Even if this study was originally intended for the implementation of finish hard turning that can replace finish grinding, the methods developed can be used to improve the final form accuracy of cylindrical workpieces in other finishing processes including grinding if any workholding devices similar to chucks are used to hold the workpieces. The methodology and the procedures for improving chucking accuracy are covered in a pending patent by the authors.

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