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เนื้อหาย่อ : PREFACE TO THIRD EDITION Ix this revised edition, a number of additions have been made, and revisions introduced where appropriate. Perhaps the most important addition is the inclusion of full data on the new I.S.O tolerance system which has finally replaced its I.S.A. forerunner. The section on ball bearing tolerances was revised in the 2nd edition, in view of the progress made by bearing makers to improve standards in this field progress still, however, considered by many to be inadequate. far as possible all other data and tables have been checked through and revised to latest practice. Acknowledgments are gratefully paid to the British Standards Institution for permission to reproduce from some of its standards; to the Newall Company for assistance with information on its limit system and for the supply of illustrations; to Messrs. Chesterman, J. E. Baty, Ltd Alfred Herbert, Solex, Coventry Gauge and Tool Co., and Sigma Instruments for similar assistance with other illustrations. Other sources of information, particularly on special processes, are indicated at the appropriate place. PREFACE TO FIRST EDITION THE use of tolerances, limits, and fits in engineering design is an essential factor in modern manufacture, whether by mass, batch, or even job production. It is surprising, therefore, that there appears to be no publication which explains the scope of the various pub- lished limit systems, and endeavours to instruct the designer in the proper use of such systems. The gulf between designer and shop man--a gulf into which many platitudes have been cast-is not made less by the ignorance f the average designer of the meaning and significance of tolerances and its, nor of the practical man of interchangeability requirements. This book, therefore, is an attempt at a clarification of the position, the prime object being to persuade the designer to use tolerances and limits with sincerity and genuine intention, both shop man and inspector then being in a position to treat the designer's drawings with more respect than is current in most production shops to-day.