Non metallic materials

Non-metallic materials are used extensively in industry for a wide range of applications, sometimes because metal would be unsuitable and sometimes because mass production is quicker using non-metals.

Wood

When we say “wood” we usually think of joiners and carpenters, but wood has its uses in engineering as well. File handles are made of wood and it can also be used for patterns in foundry work. Wood can also be used for making models of finished products, because it can be machined at high speeds and any mistakes made will result in less tool damage.

When using wood for the purposes mentioned above, a hard wood should be selected -its closer grain structure will prevent cracking and splitting when machining.

Wood can be classified as "soft woods" and "hard woods".

Soft woods are obtained from coniferous trees such as pine, spruce, larch and lime.

They are softer, easier to cut and not as hardwearing as hardwoods. They grow faster and are usually lighter in colour. The grain of the wood is very easy to see, showing as dark lines on a pale background.

Soft woods are cheaper than hardwoods. They are used a lot in the building industry for roofs and window frames. Softwood is often known as “pine” or “deal”, making no distinction between different types.

Two examples of softwood are:

• REDWOOD – is honey-coloured, with very definite grain lines and knots. It is usually straight grained and easy to cut with saws and planes. It is used a lot for house roofs, window frames and skirting boards.
• PARANA PINE – is a pale yellow colour with attractive reddish brown streaks. It is often used for good quality joinery, such as staircases or window boards.

Hard woods are obtained from non-coniferous trees such as oak, teak, ash, beech, mahogany, lignum vitae and elm.

They are harder and heavier than softwoods. They come from many different parts of the world and in many different colours. Hardwoods are generally used in high quality work, such as furniture.

Two examples of hardwood are:

• MAHOGANY – is reddish brown in colour and is both hard and strong. It is often used for top quality furniture.
• BEECH – is pinkish brown in colour with small gold flecks. It is used for mallets, workbenches and wooden kitchen tools. It is also used for a lot of school furniture.

Woods can be seasoned naturally by allowing them a period of time between their cutting down and use, this is to allow the wood to "dry out" and become stable. Nowadays, this is now more often than not obtained by an artificial process such as drying in a kiln. Seasoned wood can then be used without it buckling or shrinking in service.

Wood has the advantage of being readily available, relatively cheap, easily cut to shape, some woods are reasonably hard and strong, light weight, easily protected and coloured and also have a good natural appearance. Disadvantages include a need for protection against rotting, and being inflammable.

Manufacturing Boards

Manufacturing boards are made by cutting up solid timber and sticking it back together again in a different way. Although this sounds strange, it is a good way of making large, flat boards. Large boards cut directly from a tree trunk are quite strong but they will not stay flat.

• Plywood is made by sticking together many thin layers of wood called veneers. Each layer has its grain in the opposite direction to the ones next to it. This keeps the boards flat and makes them very strong compared to a piece of hardwood or softwood of the same thickness. It is used for things like drawer bottoms, toys and interior doors. It is often very thin.

• Blockboard is made by glueing strips of softwood side by side, and then sticking a thin veneer on each side. It is made in thicknesses from 12 mm upwards I and it is very strong. Blockboard is often used for making modern furniture, frequently with a decorative veneer on the surface.

• Chipboard is made by glueing and compressing together thousands of tiny bits of wood. It is not very strong and it is difficult to join. Its great advantage is that it is cheap. It is often used with a facing veneer for modern furniture, such as kitchen cupboards.

• Hardboard is made by glueing and compressing pulped wood. One side is rough and the other smooth. It comes in thin sheets and is used to cover large areas cheaply, such as cupboard backs. It is not very strong.