Abstract: In the national standard, GB/T 11336-2004, the results of some groups of datas processed on the pole calculus method for minimum tolerance zone evaluation of the straightness error in a plane are against the principal of minimum tolerance zone method, i.e. high-low-high or low-high-low, that means the pole calculus method exists some incompleteness. To solve this problem, the evaluation method of pole searching in certain direction and iteration is proposed. Theoretical analysis and the processing results of straightness error in a plane have proved that the method of pole searching in certain direction and iteration coincides well with the minimum tolerance zone principal in the straightness error evaluation, i.e. high-low-high or low-high-low. The processing results of data also show that the new method has good completeness and reliable precise evaluating results and the evaluating process of the new method is more efficient and absolutely convergent .Particularly, the new method can overcome the defects of the pole calculation method of the straightness error in a plane existed in the national standard, GB/T 11336-2004.

Key words: Iteration, Minimum tolerance zone, Pole calculate method, Searching in certain direction, Straightness error