ISO 8785 pdf download.Geometrical Product Specification (GPS) — Surface imperfections — Terms, definitions and parameters
1 Scope
This International Standard defines terms relating to surface imperfections in order to establish a common vocabulary to be used in technical documents, technical drawings， scientific publications, etc. to specify to what extent surface imperfections are allowed and to aid in the specification of methods of measuring surface imperfections. The surface imperfections defined in this International Standard are not related to surface roughness1) or surface waviness. It does not specifty the desirability or undesirability of surface imperfections， which depend on the application or function of the surface. For specific applications and manufacturing processes, additional terms and definitions may be necessary. Such terms and definitions will be specified in relevant International Standards. Some types of specific surface imperfections are defined in other International Standards as well.
2 General
2.1 reference surface surface, having the form of a geometrical surface, from which the parameters of surface imperfections are assessed NOTES 1 The reference surface passes through the highest peak of the real surface excluding the imperfections, and is equidistant from the mean surface determined by the least- squares method. 2 The reference surface is determined over a specified surface area, or over a limited part of the surface area related to the size (dimensions) of a single imperfection, the size of the area being sufficient to assess the imperfection while suppressing the influence of form deviation on the assessment. 3 The reference surface coincides in practice with the surface of the area adjacent to the imperfection. 2.2 surface imperfection evaluation area A portion of the real surface or the whole real surface of a workpiece on which surface imperfections are specified and inspected 2.3 surface texture repetitive or random deviations from the geometrical surface which form the three-dimensional topography of the surface NOTE – Surface texture includes roughness, waviness, lay，imperfections and form deviations over a limited surface area. 2.4 surface imperfection SIM element, irregularity or group of elements and irregularities of the real surface unintentionally or accidentally caused during manufacture, storage or use of the surface NOTES 1 It is recommended not to use the term “surface defect” for the meaning defined here (see definition of “defect” in ISO 8402) 2 Such types of elements or irregularities differ considerably from those constituting a rough surface. 3 The presence of imperfection on the real surface does not necessarily mean that the given surface is unsuitable for use. The acceptability of an imperfection is dependent on the application or function of the surface and is specified in appropriate terms, e.g. length, depth, width, height, number per unit area, etc.
4 Specific types of surface imperfections
4.1 recession inwardly directed surface imperfection 4.1.1 groove surface imperfection which is a longitudinal recession with a rounded or flat bottom See figure 1 .4.1.2 scratch surface imperfection which is a recession of irregular shape and unspecified direction See figure 2.4.1.3 crack linear recession with a sharp bottom resulting from a disturbance of the integrity of the surface, and of the parent material of the workpiece See figure 3.4.1.4 pore cavity of very small size with steeply sloping walls and, normally, sharp edges, where the upper edges of the cavity are not higher than the tangential reference surface See figure 4.4.1.5 blowhole surface imperfection in the form of a single recession resulting from the loss of foreign particles, from etching or from the effect of gas See figure 5.4.1.10 dent hollow with no raised portion, often caused by plastic deformation resulting from an impression or blow See figure 1 0.