Effect of datum surface roughness on parallelism and perpendicularity tolerances in milling of prismatic parts

Abstract

Surface roughness of the datum face is an important criterion to be considered for the selection of the datum during set-up planning as it can affect the tolerances among features. In this work, an experimental study on the effect of datum surface roughness on parallelism and perpendicularity tolerances in machining of prismatic parts by milling is carried out. A simplified mathematical model is developed to analyse the experimental findings. Statistical analysis of the experimental results has also been carried out. It is observed that sometimes a rough datum can provide better parallelism and perpendicularity than the smooth datum. Thus, the surface roughness of the datum should be decided judiciously considering the prescribed geometric tolerances and machining characteristics on a particular machine tool as well as the required surface integrity.