The production and conversion of wood into workable material underpins the entire craft of woodworking.
First, imagine a tree with a trunk that is 2 feet in diameter. The tree is 40 feet long. This would amount to a volume of timber of 3.5cu m. If you think of a billion trees like this that equates to the worldwide timber consumption each year.
Not all of this prodigious number of trees are converted into useful wood products, though. More than half is burned for fuel. Much of the remainder is converted into wood pulp for the paper and packaging industries.
The way in which trees are being cut down now is starting to have serious effects on the environment. This is not something that can be covered adequately in this article so watch this space for an upcoming post about this distressing side of deforestation.
Timber production is a huge global industry. The route traveled by a piece of wood before it reaches your workbench is varied and complex.
The home woodworker has a vast range of options available when specifying the quality and form of material to get the best results and reduce waste.
From the instant a tree is selected for felling, it’s subjected to a continual process of evaluation to grade its quality and most valuable content. When it gets to the sawmill, it will be allowed to “rest” for a while. This allows the natural tensions within the trunk to normalize. It’s then converted into large slabs for seasoning.
A skilled operator knows how to convert the log into the greatest quantity of usable timber with the minimum amount of waste.
As with most things, the higher the quality of product, the higher the cost. The way in which the log is converted to convenient sizes can affect this dramatically.
Understanding the different methods and terminology will help you to get the correct wood for your needs. It will also assist you to predict its behavior under different conditions.
The appearance of the cut surface, the amount of waste and the way in which the wood shrinks as it loses moisture are all affected by the conversion method.
Timber conversion is the process of turning logs into planks or boards which are ready to use.
When assessing the log, several factors are taken into account. The size of the taper is important. This determines how the log will be cut in order to get the very best out of the timber. Other crucial elements to weigh up are the size of the boards required, cracks or rot in the log as well as its roundness.
The way it is cut differs…
Through and through cutting
The quickest and least wasteful method of converting the log (or baulk) of timber is to make a series of parallel cuts along its length. This process is known as through and through cutting (sometimes abbreviated to T/T).
This style of cutting is normal for most large-scale commercial sawmills. It yields large quantities of boards with a tangential figure, the cuts being made across the growth rings. This produces the familiar cone-shaped pattern on the face of each board.
Such boards are described as plain sawn, flat sawn or slash sawn.
Many species of wood with distinctive or contrasting growth rings are shown to their best advantage when converted in this manner. To maximize the yield of the highly figured boards, the entire baulk can be plain sawn.
In contrast, when a log is cut into quarters and sawn radially – at right-angles to the growth rings – with the cut passing through the center, the figure displayed is quite different.
This method, though, is wasteful of timber and also very time-consuming. This is because the log needs regular repositioning on the saw table.
True quarter-sawn timber, with the cut surface intersecting the growth rings at a right angle, is only produced when the quality or the decorative value of the timber warrants it.
Boards described as quarter sawn from the supplier will have been cut by one of several methods. These are a compromise and accept the rings running at any angle of more than 45 degrees from the face.
Another option is rift sawing boards. This is when the log is split horizontally then sawn through and through vertically. By using this approach, it’s possible to produce boards with a higher proportion of quartered grain. Sometimes this is described as one square edge. It can yield high quality material at a much lower cost.
Although the quarter sawn route is rather expensive, the result is more decorative. It is also less likely to distort. It will contract and expand less than timber sawn using alternative methods.
The plain method, on the other hand, results in quarter sawn material which is pretty close to the center of the log. This creates a pattern in the shape of a flame. When timber is converted with this particular method, it has a tendency to cupping. If handed correctly, it is actually stronger.
Note: before the wood is converted, the first stages are to process it and then season it.
If you are passionate about woodworking then simply buying a few tools is not enough.
In order to work well with wood, it’s a smart idea to think about where it comes from and how it gets from the forest to your workbench.
Next week we will take a look at some handy hints for seasoning wood.
Enjoy your woodworking but take your time to fully understand all aspects of the craft. By taking the time and trouble to learn as much as you can about the material you are working with, you’ll notice that your confidence will grow and the quality of your work will improve.