BS EN ISO 8785:1999 pdf – 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 roughness 1) or surface waviness. It does not specify 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 NOTE 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. NOTE 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. NOTE 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 NOTE 1 It is recommended not to use the term “surface defect” for the meaning defined here (see definition of “defect” in ISO 8402) NOTE 2 Such types of elements or irregularities differ considerably from those constituting a rough surface. NOTE 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.
3 Characteristics and parameters of surface imperfections NOTE The maximum value of parameters and characteristics of surface imperfections allowed on a surface is that value applied for specification, i.e. the limit beyond which the component containing the imperfection is rejected. EXAMPLES SIM n = 60 where SIM n is the surface imperfection number as defined in 3.7 SIM n /A = 60/1 m –2 SIM n /A = 10/50 mm –2 where A is the surface imperfection evaluation area as defined in 2.2 3.1 surface imperfection length SIM e greatest dimension of the surface imperfection, measured parallel to the reference surface 3.2 surface imperfection width SIM w greatest dimension of the surface imperfection, measured normal to the surface imperfection length and parallel to the reference surface 3.3 single surface imperfection depth SIM sd greatest depth of the surface imperfection, measured from and perpendicular to the reference surface 3.3.1 combined surface imperfection depth SIM cd distance between the reference surface and the lowermost point of the surface imperfection, measured from and perpendicular to the reference surface 3.4 single surface imperfection height SIM sh greatest height of the surface imperfection, measured from and perpendicular to the reference surface 3.4.1 combined surface imperfection height SIM ch distance between the reference surface and the uppermost point of the surface imperfection, measured from and perpendicular to the reference surface