Abstract: Cutting with machine tools is an expensive activity, in which even little progress achieved in technology can produce great results. The problem of low stiffness to weight ratio of the rectangular-box-like machine tools has been partially solved with the introduction of Stewart platform. Having six degrees of freedom it executes the positioning of the end-effector in space. The objective of this study is to analyze stiffness of 3-3 Stewart platform using the mathematical model developed based on inverse kinematics for Spiral contours. The set of positions and orientations to be followed by the tool for different contours in terms of the moving platform for maximum stiffness are synthesized. Two planar contours are taken for the purpose of the analysis. The results obtained would serve as a tool in the hands of a design engineer to model the often ignored parameters. This method provides us with set of positions and orientations of the moving platform that should be executed throughout the machining process for a given contour in order to have maximum stiffness of the Stewart platform. The results obtained are to be validated for singularity-free path planning and attempt has to be made to estimate the computational efficiency of the algorithm.