BS ISO 2426-1:2020 pdf download – Plywood — Classification by surface appearance Part 1: General This document establishes general rules for the classification of plywood by its surface appearance. It concerns plywood made of hardwood including tropical and temperate hardwood, softwood and plywood derived from other lignocellulosic materials. It does not apply to overlaid plywood. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 2426-2, Plywood — Classification by surface appearance — Part 2: Hardwood ISO 2426-3, Plywood — Classification by surface appearance — Part 3: Softwood 3 Terms and definitions No terms and definitions are listed in this document. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https:// www .iso .org/ obp — IEC Electropedia: available at http:// www .electropedia .org/ 4 Classification by surface appearance 4.1 Classes Classification of plywood by surface appearance is made according to the number and the extent of certain natural characteristics of wood and the defects that come from the manufacturing process. Five appearance classes are distinguished, identified with the following codes: E, I, II, III, IV. 4.2 Characteristics and defects taken into consideration 4.2.1 Determination of appearance class Determination of the appearance class, based on the appearance of the panel surfaces, shall take into account the categories of characteristics given in Table 1 and defects given in Table 2. 4.2.2 Characteristics inherent in wood Categories of characteristics inherent in wood are listed in Table 1. 4.3 Classification by appearance of panels The appearance class of plywood is determined by the classes of its surfaces. The class of the plywood first describes the class of the face followed by the class of the back. 5 Rules for classification 5.1 Classification for hardwood and softwood The permissible characteristics and defects for each of these appearance classes of this document are specified in ISO 2426-2 for hardwood and in ISO 2426-3 for softwood. 5.2 Conditions of admissibility for inherent characteristics of wood, and manufacturing defects 5.2.1 General Characteristics and defects which are limited in number, size, or extent are either enumerated or evaluated over the total surface of the panel. This number or extent is expressed par square metre of panel, with the exception of checks, splits and open joints which are related to one metre of panel width. The number and the extent of characteristics and defects shall be defined as follows and rounded off to the nearest unit. a) For knots and holes: 1) individual diameter; 2)...
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