tailieunhanh - Dimensioning and Tolerancing Handbook Episode 2 Part 1

Tham khảo tài liệu 'dimensioning and tolerancing handbook episode 2 part 1', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 5-156 Chapter Five the profile tolerance of .010 establishes a discrete profile tolerance zone for each individual feature. As with the Level 2 size limit boundaries for holes in a pattern there is no basic relationship between these Level 2 profile zones. They are all free to float relative to each other and relative to any datums. Note If the Level 2 feature control frame were added as a third segment of the composite control the Level 2 profile zones would be basically related to each other. Of course the Level 2 tolerance must be less than any pattern-controlling tolerances to have any effect. Composite Profile Tolerance for a Single Feature For features of size different characteristic symbols denote the four different levels of control. But for irregularly shaped nonsize features the same profile of a surface symbol is used for each level. In Fig. 5-144 for example we want to refine a bounded feature s orientation within the constraints of its locating tolerance. Simply stacking two single-segment profile feature control frames would be confusing. Many people would question whether the .020 tolerance controls location relative to datum B. Instead we ve borrowed from pattern control the composite feature control frame containing a single entry of the profile of a surface symbol. Though our pattern has only one feature the tolerances mean the same. Figure 5-144 Composite profile tolerance for a single feature In Fig. 5-144 the upper segment establishes a .080 wide profile tolerance zone basically located and oriented relative to the DRF A B C. The lower segment provides a specialized refinement within the constraints of the upper segment. It establishes a .020 wide zone basically oriented but not located relative to the DRF A B. All the rules given in section governing datum references tolerance values and simultaneous requirements apply for a composite profile pattern of one. Symmetry Tolerance Symmetry is the correspondence in size .