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woodoworking

 

Changes in temperature and relative humidity cause wood to expand or contract, explaining why wood expands in winter and contracts in summer. Most timber shrinkage or expansion occurs across the grain (ie across a plank).

So a basic rule of woodwork is to avoid gluing timber components with end grain to long grain. An example is a solid wooden table top with mitred edges. As the timber tries to expand or contract, the mitred ends prevent it from moving, causing glue joints to fail and the top buckling or cracking. Finishes can decrease the level of movement, but are unable to completely prevent it from occurring.

The ability to allow for timber movement and a critical understanding of the properties of each type of timber ensures precise, handcrafted furniture that will last a lifetime. 

For those interested in exploring timber movement in more detail, the Wood Movement Calculator 3.1 (an Excel spreadsheet), provides a quick and simple way of estimating the amount of timber movement based on weather patters in moisture content. There are separate estimates for Australian and other timbers. You can download the calculator here.