meter of surface. Plywood second-class standard, can have knot diameter not exceeding 40 mm, plywood third grade there may be knots maximum diameter of 70 mm. On the plywood of the fourth grade this indicator .Chastichno accreted, unjoint, loose knots, knot holes and wormholes. This kind of defects are totally unacceptable a veneer of elite varieties. Plywood Class I: may be up to three listed defects per 1 sq.m. surface, if their diameter is less than 6 mm or 10 mm if the hole sealed with putty. Plywood second grade: standard allows the presence of no more than 6 such defects per 1 sq.m. diameter of 6 mm, clamped putty – 15 mm.
Plywood third grade: it is assumed the existence of an unlimited number of these defects with a diameter up to 100 mm, plywood fourth grade are allowed any number of defects with a diameter up to 400 mm. Closed splits. Serried edge cracks should be held tightly to each other. Plywood elite class does not admit the existence of these defects. Plywood grades 1.4 allows unlimited number of cracks, provided that they do not impair performance characteristics. Diverged cracks. Standard does not permit the presence of dispersed cracks in the elite grade plywood. In the first plywood varieties may be present 1.2 cracks up to 250 mm and a thickness of 3 mm, if they are sealed with putty. In plywood Class ii 3.1 crack lengths up to 400 mm in diameter and 5 mm. Plywood 3 grades: 1-3 cracked up to 600 mm, a width of 10 mm.