Can ISO GPS and ASME Tolerancing Systems Define the Same Functional Requirements?

Geometrical tolerances are defined in the ISO Geometrical Product Specification system that is used worldwide, but on the other hand, the ASME Y14.5 standard is used in American companies to define how far actual parts may be away from their nominal geometry. This paper aimed to investigate whether specifications defining acceptable geometrical deviations in one system can be transformed to specifications in the other system. Twelve selected cases are discussed in the paper. Particularly, two cases of size tolerance, three cases of form tolerances, one case of orientation tolerance, four cases of position tolerance (including position tolerance with MMR for the pattern of five holes) and, finally, two cases of surface profile tolerance (unequally disposed tolerance zone and dynamic profile tolerance). The issue is not only in the several different symbols and a set of different defaults, but also in the different meanings and different application contexts of some symbols that have the same graphical form. The answer to the question raised in the paper title is yes for the majority of indications specified according to ASME Y14.5 when new tools from the 2017 edition of ISO 1101 are applied.

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COMPLEMENTING AND ENHANCING DEFINITIONS OF LINE PROFILE COMPOSITE TOLERANCE IMPOSED BY ISO GEOMETRICAL PRODUCT SPECIFICATION

Journal of Machine Engineering ◽

10.5604/01.3001.0012.0934 ◽

2018 ◽

Vol 18 (2) ◽

pp. 75-85

Author(s):

Yiqing YAN ◽

Martin BOHN

Keyword(s):

Line Profile ◽

Geometric Feature ◽

Theoretical Level ◽

Tolerance Zone ◽

New Approach ◽

Physical Behaviour ◽

And Function ◽

Product Specifications ◽

Geometrical Product Specification ◽

Product Specification

According to the ISO Geometrical Product Specifications (GPS), if two or more specifications of the same characteristic are to be indicated, they may be combined as a composite tolerance. Therefore there are no definition differences between the single separate tolerance indicators and their composite tolerance, which is different from the ASME standards. Hereby, the definitions of the combined tolerance which specifies the additional location, orientation and form of tolerance zone are not explicitly defined in the current ISO. It restricts the required definitions of tolerance specifications of a component which are often utilized in practice. However, the required definitions cannot be notated in the technical drawings by using the ISO semantics, because the ISO definitions are insufficient. It causes definition gaps and misinterpretations. This paper focuses on developing the definitions of line profile composite tolerance and suggests a new approach for explicitly defined and function-oriented systematology of line profile composite tolerance. This research is based on the analysis of physical behaviour of geometric feature of a component on a theoretical level. Completed and enhanced definitions in an improved systematology for line profile composite tolerance is formulated which fills the definition gaps and eliminates the deficits in ISO GPS.

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