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เนื้อหาย่อ : This is a text about technique, not about hardware. Its objective is to develop dimensional measurement ability for skilled workers, inspectors, technicians and for those going on into engineering and science. Its premise is that these skills can be acquired best when knowledge accompanies practice. There are many books that treat dimensional measurement as an aside to other disciplines from machine operation to quality control. Here the primacy of meas- urement is recognized as the common element without which there could be no crafts, no manufacturing, and no science. This has long been recognized in England, Europe and the Soviet Union. The author has borrowed freely from their experience. Communicative, as well as manipulative, aspects are stressed because the se- inspector, mantic differences separating the production worker, skilled worker, gagemaker, engineer, quality-control person, metrologist, and research worker are now a recognized deterrent to continued progress. Although these subjects are not taught as such in this text, the student will become familiar with the principles, terminology, and instrumentation common to them all. Recognizing that this book will be used in terminal courses, and that its language will carry into employment, the recently adopted decimal-inch terminology has been used wherever possible. The science student need only make a few transpositions, such as "part" to ''object', "inspector" to "observer" to adapt the material for his needs. Metric information is included for the immediate needs of the science student and to prepare the indus- trially oriented student for the possible extension of the metric system in the United States. The relationship between systems and commercial standards is shown. The book begins with the reasons for communication by measurement. The basic considerations are developed first with the lowest-precision instruments. Each following chapter then advances these basic considerations to successively higher levels. The importance of the standard of length, cleanliness, alignment, and recognition of uncertainty is reinforced at each level. Practical applications are included throughout to give relevance to the theoretical aspects. Two devices have been used to adapt the book to the diverse curriculums to which it is directed. The chapters are subdivided into smaller units which are nearly com- plete within themselves. Although this necessitates some duplication, it enables the educator to select as much or as little as suits his needs. Similarly, one instru- The laboratory ment is chosen in each area to best explain the basic considerations. experiment book, however, permits the hardware aspects to be treated as extensively as each curriculum requires. Controversial subjects have neither been avoided nor dispensed with by doctri- naire pronouncements. The student is told of the conflicting views and invited to join in the arguments. A casual style is attempted, including free use of vernacular measurement terms and anecdotes where appropriate. No attempt, however, has been made to write down to the least interested student who will probably make the least use of the material anyway. Previous knowledge of geometry, algebra and trigonometry is very desirable, but not essential.