BS ISO 2426-1-2020 pdf free 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) cumulative diameters, expressed per square metre of panel surface.
NOTE The diameter of a knot or hole is conventionally defined as the diameter across the general direction of the grain of the veneer.
b) For checks, splits and open joints:
1) individual length;
2) individual width;
3) number per metre of panel width.
5.2.2  Joints
In appearance classes I to IV, the number and the width of veneers which form the outer plies of a panel are not restricted, provided the joints are well made.
The veneers forming the outer plies of class I shall be well matched for colour and have similar grain.
The outer plies shall be laid with the joints approximately parallel to the edges of the panel.
In class E, the outer ply using rotary-cut veneer may be of one or two veneers provided that the joint is well made, approximately at the centre of the panel, approximately parallel to the edges of the panel and that the veneers are well matched for colour and of similar grain.
5.2.3  Inclusions
The inclusion of foreign particles likely to damage the machining equipment is not permitted.
5.2.4  Repairs
Patches and shims used for the repairs shall fit and be properly fixed. The matching for colour and grain shall be in accordance with the requirements for the appropriate appearance class.
Synthetic filling is permitted, subject to the appearance class requirement.BS ISO 2426-1 pdf download.