Effects of support misalignments in deep-hole drill shafts on hole straightness

This work investigates the effect of drill shaft support misalignment on hole straightness in relation to the various control factors. Misalignments occur in machine spindles, intermediate supports and pilot bushings. Equations for axial hole straightness deviation are derived herein using the Euler column theory, and experiments are performed using Gundrill and BTA deep-hole drilling systems. Simulation results, Sakuma's method and experimental examinations are also presented. Taguchi methods and statistical techniques are used to formulate the experimental layout, analyze the effect of each control factor on the results, and optimize the setting for each control factor. Further experiments then verify these estimates. Six control factors were used in a modified L8 orthogonal array design. The confirmatory experiments revealed an average straightness deviation within the 95% confidence interval. (C) 2001 Published by Elsevier Science Ltd.