Plywood

Plywood is a manufactured wood panel from the family of manufactured boards (such as medium-density fibreboard (MDF),particle board (chipboard), etc.) made from thin sheets of wood veneer. Plywood layers (called veneers or plies) are glued together, with adjacent plies having their wood grain rotated relative to adjacent layers up to 90 degrees.

All plywoods bind resin and wood fiber sheets (cellulose cells are long, strong and thin) to form a composite material. This alternation of the grain is called cross-graining and has several important benefits: it reduces the tendency of wood to split when nailed at the edges; it reduces expansion and shrinkage, providing improved dimensional stability; and it makes the strength of the panel consistent across all directions. There is usually an odd number of plies, so that the sheet is balanced—this reduces warping. Because plywood is bonded with grains running against one another and with an odd number of composite parts, it is very hard to bend it perpendicular to the grain direction of the surface ply.

Grades of Plywood

As you have understood from the above paragraph, A, B, C, D are grades of plywood commonly used. When you have a look at the plywood, you will find the letter grades are printed in pairs. These plywood grades explained here, will help you understand their hidden meaning. This means, if one side is printed with A and the other side with C, it indicates that the plywood has a well finished front side and a slightly unfinished back side. Construction grade plywood is graded as C-D and called CDX plywood. The best way to explain grades of plywood is by understanding the types of plywood. Let us have a look at the four basic types of plywood.

Marking of Grades

Plywood is generally available in 4'x8' sheet and is cut into a square board. The thickness of plywood normally used is 1/8", 1/4", 1/2", and 3/4". The 1/8" and 1/4" plywood is used for making hard covered flats. 1/2" plywood is used for building furniture parts, boxes and props. It is lighter as well as cheaper than 3/4" plywood. Lastly, 3/4" plywood is used to make covering platforms as it is very strong type of plywood.