Based on the idea that the dynamic performance of a machine-tool should be evaluated in terms of its machining accuracy, a new test method is proposed which uses the machined surface as a measure of performance evaluation. The cross sectional profile of the machined test piece surface is measured in the direction orthogonal to feed direction, and nine different indexes which characterize the profile are extracted. These indexes are then checked based on the concept of SN ratio to select "straightness error of the profile" as the best one. Finally eight different machining centers are tested by using the performance index thus determined to confirm the validity of the method.
