8.25 - WOOD: Revision Sheet

Advantages of wood • Wood is easy to work . • It glues easily. • It is warm to the touch. • It has an attractive appearance. • It is easy to obtain. • It is reasonably cheap. • Wood is electric and heat insulating.

Disadvantages • Protection is usually needed against insect and fungal attack. • It can warp and shrink as it dries. • Wood easily splits along the grain. • It cannot be cast like metal. • It's size is limited by the tree size.

There are two main types of wood - hardwoods and softwoods.

SOFTWOODS
Softwoods come from conifer trees. They are generally softer than hardwoods, hence their name. The wood is commonly called pine in the shops. The building trade uses softwoods for most of its construction work because of its cheapness and availability.

Some softwoods
Scots pine (brown or yellowish) It is used for joinery work.
Cedar (reddish brown) A very useful outdoor wood, e.g. for cedar greenhouses, window frames. It is a fairly soft wood.
Spruce (white to yellowish brown) It is used for construction work, oars and gliders etc. It is strong for its weight.
Yew (orange to dark brown) It is fairly expensive and is used for veneers and wood turning.

HARDWOODS
Hardwoods come from deciduous trees (most of which are hard, hence the name of this group). Deciduous trees have broad leaves which are 'shed' in the winter. There is a great range of hardwoods, from the quite soft 'hardwoods', e.g. balsa wood, to the very hard hardwoods such as ebony.

Some hardwoods
Oak (light brown) A very hard wood, often used for furniture and decorative veneers and general high quality work. (Steel screws rust in oak; brass screws must be used instead.)
Beech (light brown or pinkish) A tough close-grained wood making it suitable for tool handles, unpainted toys, rolling pins, furniture and work benches.
Ash (whitish) A hard tough wood used for sports equipment, handles and internal joinery.
Mahogany (reddish brown) It is used a great deal for veneers on chipboard. A very decorative wood used for high-class furniture. (Many varieties of mahogany are available.)
Teak (light brown) It is used for high-class furniture, tables, boats etc. It is resistant to decay.
Balsa (white) Although it is very soft, it is in fact still in the hardwood category because it is a deciduous wood. It is used for model making.
Obeche Light coloured and soft to work.

Manufactured boards
Manufactured boards are processed timber. They have new and useful properties.

MDF (medium density fibreboard) is now widely used.
Plywood made up from alternating layers of thin sheets of wood is strong in all directions.
Chipboard made from softwood chips and sawdust is cheap but only attractive when coated with melamine – used for kitchen cupboards (carcases).