Plywood is made of three or more thin layers of wood bonded together with an adhesive. Each layer of wood, or ply, is usually oriented with its grain running at right angles to the adjacent layer in order to reduce the shrinkage and improve the strength of the finished piece.
How many layers in plywood?
So before I tell you about plywood material, you should know that a plywood is made of thin layers of wood which are stuck together using a strong adhesive. There are mainly two types of plywoods – construction plywood and industrial plywood, and hardwood and decorative plywood.
I am not going into the technical aspects of grading of veneer but you should know that a common plywood generally has 3 or more layers.
It must be noted that these layers or piles, as we call it, are usually in odd numbers only. The number of piles required will depend on the thickness required in the plywood. Here is a table for your reference:
|Plywood Thickness(mm)||Number of Plies (including face veneers)|
|3.6||3 or 5|
|5.2-6.5||5 or 7|
|9||7 or 9|
|12||9 or 11|
|15||11 or 13|
|18||13 or 15|
|21||15 or 17|
|25||17 or 19|
Sizes and number of layers
|Thickness, mm||Number of layers||Plywood Sanded||Plywood Not Sanded|
|Thickness tolerances, mm||Thickness variance, mm||Thickness tolerances, mm||Thickness variance, mm|
|4||3||+0,3 | -0,5||0,6||+0,8 | -0,4||1,0|
|6,5||5||+0,4 | -0,5||0,6||+0,9 | -0,4||1,0|
|9||7||+0,4 | -0,5||0,6||+0,1 | -0,5||1,0|
|12||9||+0,5 | -0,7||0,6||+1,1 | -0,6||1,0|
|15||11||+0,6 | -0,8||0,6||+1,2 | -0,7||1,5|
|18||13||+0,7 | -0,9||0,6||+1,3 | -0,8||1,5|
|21||15||+0,8 | -1,0||0,6||+1,4 | -0,9||1,5|
|24||17||+0,9 | -1,1||0,6||+1,5 | -1,0||1,5|
|27||19||+1,0 | -1,2||1,0||+1,6 | -1,1||2,0|
|30||21||+1,1 | -1,3||1,0||+1,7 | -1,2||2,0|
Plywood of different thicknesses and number of layers is possible to produce by agreement between customer and producer.
|Length and width of plywood sheets||Size tolerances|
Plywood sheet length is determined along the grain of face veneers.
Plywood sheets must be cut at a right angle.
Slant must not exceed 2 mm per 1 m of a sheet edge length. Deviation from edges straightness must not exceed 2 mm per 1 m of a sheet length.