A Survey of Surface Quality Standards and Tolerance Costs Based on 1929-1930 Precision-Grinding Practice

Abstract In an earlier paper presented at a meeting of the Chicago Section of the A.S.M.E. on March 18, 1929, the author reviewed the process of evolution through which the art of precision of cylindrical grinding had passed up to that date. This paper reviews some of the defects which exist in the present-day accepted standards of finish of mechanical components, and represents an endeavor to maintain continuity by carrying the discussion through to the present-day standards of finish attainable by the abrasive process. It is pointed out that it is useless to specify extremely close limits of accuracy unless the measurements are made across basically plane surfaces. Size control and its effect on cost of production, as well as the length of useful life, is discussed, and better finishes are advocated as a means of reducing the ill effects of high initial wear. A scheme for the establishment of definite standards of finish is put forward, and a finish-calibrating instrument is described. Emphasis is laid on the fact that there is no available short-cut method of obtaining ultra-fine-finished surfaces with a minimum of initial wear, and the author points out that standardization of finishes can be attained at low cost with little disruption of present methods; also that the subject of longer useful life to mechanical components is closely interlocked with the provision of a better standard of finish and the attendant benefits derived from close adherence to true limits of accuracy.