Different types of wood

Manufactured board



- We use manufactured board rather than wood because the wood may still be moist and could change shape or rot (a lumber is usually around 70% water).

- Another reason is because it is widely available compared to wood.

- Manufactured board comes in sizes every 3mm. This is because it is much easier and more efficient for manufacturers as well as consumers.

- The average size of a piece of manufactured board is 1.24m X 2.44m (8'X4').

- Woods can be made stronger by laminating with the layers' grains facing the other way each layer.



Different woods

- Plywood: laminated from thin veneers. The main reason for using plywood instead of plain wood is its resistance to cracking, shrinkage, twisting/warping, and its general high degree of strength. Also, plywood can be manufactured in sheets far wider than the trees from which it was made.

- MDF (medium density fibreboard): made by wood chippings and adhesive being compressed together. A problem for manufacturers is that is is sometimes too hard to cut.

- HDF (high density fibreboard): made by the same process but compressed more.

- Chipboard: used in kitchens a lot. It's very cheap to make and relatively strong, so usually a coating is applied over it to make it look good cheaply.

- Blockboard: wood sandwitched between two veneers.

- Aeroply: used in the manufacture of aircraft. Most aircraft have wooden internal frames made from aeroply.

- Maplex: new type of wood recently discovered. It's used in furniture and easy to machine.



Methods of veneering



- There are various ways to make veneers of woods, such as:

- Slice veneering: simply sawing off the thin layers of wood.

- Rotary veneer: this is a more commom method. It involves slicing the wood as the log rotates; the diameter gets smaller. I.e. like a toilet roll.



Types of finish



- Products made from wood, especially for outdoor use, need some sort of protection. The different types of finish for woods are:

- Polyurethane finish: the most common type. It protects the surface and gives a smooth, shiny finish.

- Wood stain: changes the colour of the wood. Doesn't actually protect the wood that well, so there is a need to apply a different finish as well.

- Oils: can be rubbed in to the wood to maintain its matural appearence.

- Preservative: usually used on timbers being used outdoors.

- Paint: gives the wood a strong colour as well as protecting it.



- Another way of protecting timbers is to inject a wood with tanaliser into the wood. This is why some woods look green.

It's only injected 5mm into the surface of each edge.

The process is called tanalising, and lengthens the life of the wood by around 4 times.



Metals



- Before woods, metals used to be the most commonly used material.

- Metals can be split into four different sections:

- Ferrous: contain iron & carbon

- Non-ferrous: do not contain iron

- Ferrous alloy: a mixture of 2 or more metals where at least one contains iron & carbon

- Non-ferrous alloy: mixtures of 2 or more metals that do not contain iron