Woodworker's Encyclopaedia

The Woodworker|December 2019

Woodworker's Encyclopaedia
There are a number of things that cause defects in this section of the directory. As he moves from the Cs to the Ds, Peter Bishop has a few more descriptions that he hopes you’ll find interesting
Peter Bishop

Crown

In relationship to trees, the crown is the top part that includes all the branches and foliage.

Crown cut

This is an alternative name for through and through cut logs. It literally means that the log is cut through from one side right through to the other, slice after slice. It’s a simple method that produces a variety of different qualities, including a few quartersawn boards.

Cubic measure

Most lumber is bought and sold in some form of cubic measure be it imperial, cubic feet, or metric cubic metres. A cubic foot is the equivalent of a block 1ft, or 12in square. A cubic metre is a metre cube. Historically, hardwoods were sold in cubic feet and softwoods in cubic metres, but this has blurred over time. A cubic metre, abbreviated as m3, contains 35.3147 cubic feet, abbreviated as cu ft. If you only want small quantities, it’s probably easier to work with cubic feet than metres.

Cupping

This is a defect in timber and can be quite wasteful. The word is used to describe boards that have cupped, or dished if you wish, across the grain. When lumber is cut from the log there are specific boards that will have a tendency to cup more than others. When crown cut/through and through cut, as above, those boards towards the outside will be most likely to cup. If dried slowly and carefully, this can be minimal. It’s all related to the cellular structure of wood, how the planks are cut from the log and the tensions that are created when it dries. The result of cupping can be costly. If you can imagine trying to produce flat surfaces from cupped boards you will understand that a lot of waste is generated before the flatness is achieved. It also means that you’ll need to start out with something thicker than the final size you require. We’ll cover the techniques required to flatten stuff later on in the series.

Diagram illustrating the difference between ring and cup shakes

Cup & ring shakes

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December 2019