Plywood type and their uses

Plywood is a type of specially processed wood, consisting primarily of an odd number of plies (or thin sheets called veneers) glued together so that the grain of adjacent layers is perpendicular to each other. I am Placing the plies normal to each other increases the longitudinal and transverse strength of the plywood. The layers are held in position using suitable adhesives.

In the simplest form of plywood, the board consists of three layers or three plies arranged in such a manner that

1. One ply lies at the centre and is referred to as the central ply.
2. One ply each lies on the upper and lower surface of the central ply. One of these is referred as ‘face ply’ and the other as ‘back ply’.

Plywood should always contain an odd number of panels and this is essential to obtain a balanced product. The most important properties that make plywood so advantageous over the ordinary wood are as follows:

1. Its better resistance to shrinkage, swelling and warping, which is achieved by making these defects uniform in both the directions.
2. Its almost perfect freedom from splitting.
3. Its increased strength as compared to the same thickness of ordinary wood.

Plywood is used for various purposes such as ceilings, doors, furniture, partitions, panelling walls, packing cases, formwork for concrete, etc. Plywood, however, is not suitable in situations subjected to direct shocks or impacts.

Plywood is available in different commercial forms, such as batten board, laminboard, metal-faced plywood, multi-ply, three-ply and veneered plywood.

The batten board is a solid block with core of sawn thin wood. The thickness of the core is about 20–25mm and the total thickness is about 50 mm. These boards are light and strong. They do not crack or split easily. They are widely used for making partition walls, packing cases, furniture pieces, ceilings, shutters of doors and windows etc.

The laminboard is similar to batten board except that the core is made of multi-ply veneers. The external plies are of thick veneers and they are firmly glued with core to form a solid block. These boards have the same uses as that of batten boards.

In metal-faced plywood, the core is covered by a thin sheet of aluminium, copper, bronze, steel etc. This plywood is rigid.

Plywood prepared from more than three plies are designated as multiply. The number of veneers is odd. The thickness may vary from 6 to 25 mm or more.

Plywood made from three plies only is known as three ply. The thickness may vary from 6 to 25 mm or more.