Tham khảo tài liệu 'geometric dimensioning and tolerancing for mechanical design part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Source Geometric Dimensioning and Tolerancing for Mechanical Design Chapter 10 Concentricity and Symmetry Both concentricity and symmetry controls are reserved for a few unique tol-erancing applications. The controls employ the same tolerancing concept but apply to different geometries. Concentricity controls features constructed about an axis and symmetry controls features constructed about a center plane. Concentricity and symmetry both locate features by controlling their center points within a specified tolerance zone. They are typically used when it is important to accurately balance the mass of a part about its axis or center plane. Chapter Objectives After completing this chapter you will be able to Define concentricity and symmetry Specify concentricity and symmetry on drawings Describe the inspection process of concentricity and symmetry Explain applications of concentricity and symmetry Concentricity Definition Concentricity is that condition where the median points of all diametrically opposed points of a surface of revolution are congruent with the axis or center point of a datum feature. Concentricity applies to correspondingly located points of two or more radically disposed features such as the flats on a regular hexagon or opposing lobes on features such as an ellipse. Specifying concentricity Concentricity is a location control. It has a cylindrical-shaped tolerance zone that is coaxial with the datum axis. Concentricity tolerance applies only on a 167 Downloaded from Digital Engineering Library @ McGraw-Hill Copyright 2006 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Concentricity and Symmetry 168 Chapter Ten Figure 10-1 Concentricity has a cylindrical tolerance zone and applies at RFS. regardless of feature size RFS basis it must have at least one datum that also applies only at RFS. The feature control frame is usually placed beneath the size .
