SHAPE

摘要

Usually when we look at a drawing in the home workshop, we mentally accept its surfaces as flat, its corners as right angles, holes as circular and so on. We then make the component without overly much attention to those characteristics, and probably the part turns out to be fit for use. In former times if there were special requirements in regard to particular characteristics (for example concentricity) then these would be stated in a note on the drawing, or in the accompanying text of a magazine article or book. However in the highest classes of work, these and other features may become important and to address this need for precision, geometric tolerancing was devised at around the time of World War II. This article gives a short resume of this concept and how it is depicted on drawings, so that if you encounter such symbols on commercial drawings you will have a basic understanding of what they represent. The article also refers to some examples of the measuring equipment by which some of these characteristics may be checked to different levels of precision.