Author(s)

T.J. Morris

Abstract

For a variety of reasons 'Accuracy' and 'Repeatability' as defined by Standards are often far removed from values obtained in the workshop. This paper sets out to explore some of these reasons. 1 Accuracy Standards Standards from ISO*, along with those from diverse national bodies^'*, show us how to measure the accuracy of our machine tools. They show us specifically how, with accurate measuring equipment such as a laser and a computer, we can attach numbers to a variety of pre-defined arbitrary quantities called 'Accuracy', 'Repeatability', 'Positional Deviation' and so on. Each standard has its own way of testing and calculating such quantities, and while some of these Standards are quite similar in method and may differ only in fine detail, others can show a markedly different approach with, consequently, different results. The parameters referred to,

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