Flashcards in Wood Deck (8)
What is grain formation in timber?
Grain formation in timber is a result of the growth of wood fibres or cells.
The direction of the grain in some sawn timber can be seen by the way the rough surface texture lies. If this is not obvious a finger rubbed firmly along the surface will tend to smooth in one direction and meet resistance in the other
Cutting, length and width of a piece of timber
The length of a piece of timber is measured parallel to the grain, the width across the face and the thickness across the edge. With the grain refers to the better for planing, against the grain gives a rougher finish and across the grain means that working is done at a right angle to the length. End grain is the porous surface exposed after cutting across the grain.
Definition of softwoods
Softwoods have "naked" seeds in the form of cones. Softwood trees are also known as conifers. These trees can be describes as having "needle shaped" leaves. They are referred to as "non-pored" timbers and have a more simple uniform cellular structure.
Definition of hardwoods
Hardwoods come from trees with enclosed seeds, such as the common gum tree or euchalypt. These trees can be described as having broad shaped leaves. Hardwoods are known as “pored” timbers where larger vessles are present.
When do defects in timber occur and what do they affect?
Defects in timber may occur during growth, when the tree is felled, in milling of the timber or when seasoning (removing excess moisture from the timber).
Defects may affect strength, durability and appearance of the timber.
When a tree is cut down, it starts to dry out.
Timber with too much moisture is called 'green' timber. Green timber tends to change shape as it dries, by twisting, warping, bowing, bending or cupping. It can also shrink. Dried timber is more durable, more resistant to fungal attack, and more stable. It's also better to work with and to finish.
There are two methods of drying timber.
Air‐drying is a method where cut timber is stacked in an open pattern so that air can circulate around it. It takes a long time, and is mainly used for rough‐sawn timber.
A more accurate method is 'seasoning', where timber is placed in a kiln and slowly heated to the correct drying temperature. Seasoned timber is more expensive than air‐dried timber, and is used to make furniture, musical instruments and accurate constructions.
Face sides and edge marks
Face sides and edge marks are used to help with marking out and assembly. These signify that the surfaces are flat, straight and square, and that they are the surface from which marking out and testing is done.
The face side mark is like the top of a written "f" andthe face edge mark like an inverted' 'v". The end of the loop on the face side mark points in the direction of the grain.