Even though wood has been around as a building product for millions of years, it remains one of the most complex building products due to it inherent properties. THe more you learn about wood the more there is know, and when you are a woodworker, understanding your building medium will put you miles ahead in saved time, costs and satisfaction with your projects. Have you ever wondered why some of your woodworking projects buckle, bend or crack? Well, the answer may be the way it was built, or it could have been the "cut" of wood you used. This article will attempt to help explain some of the charcteristics of wood to help you make some better choices in selectinb your building materials and assembling your products. Click below to read more ...
If you are starting off by reading this article, stop and go back and read Part 1 of this article first, it will only take a few minutes and it will make this article much easier to understand and apply.
When we look at the three primary cuts of boards, Flat, Rift and Quarter, it is evident that the growth rings run at different angles. This is critical to understanding how wood behaves. You should first of all know that all wood is constantly moving. The reason it is constantly moving is that wood is always either absorbing or dissipating moisture. Where ever wood is stabilizes itself to the conditions around it, if the air is moist, wood absorbs moisture, if the air is dry the wood sheds moisture until it is stable with its environment.
Another thing to know about wood is that during it expansion and contractions it only moves is certain directions. Wood will not expand in the direction of the grain. To explain this a bit more, it you purchase a simple 8 foot 2" x 4" board, and put it in either a moist or dry environment, the board will not get any longer or shorter, it will always remain (with in mico meters) of its original 8 foot length.
The same 2' x 4" board in placed in moist or dry atmospheres WILL change width and depth. This is because wood absorbs water within it growth ring directions. Predicting how much a board will expand across its width and depth is very difficult because it depends on th type of wood and the cut of the board. For example a quarter-sawn board will expand more across it face than will rift sawn, and a flat-sawn will expand very minimally across its face, but it will expand a lot across its depth.
It is these same reasons, those of expansion and contraction that make Rift-sawn boards the worst culprits for turning out "propellers" (boards that are often twisted beyond use and end up as firewood).
So ... what are the pros and cons of each type of board and where should they be used?
Flat-Sawn boards are often considered the most beautiful of the cuts with the grain displaying the beautiful "cathedrals" up the grain of the board. These boards are ideal for large visual areas like kitchen cabinet doors, drawer fronts or the sides of dressers or other large similar projects. These boards are quite stable dimensionally, across their width. Where you may not want to use them are as treads when building a stair case as these boards will flex and bend under pressure, they would be great for risers on steps with the visual appeal and their strength in that direction. For treads on a stair rift would be better but quarter-sawn would be best for the treads. Flat sawn is also a poor choice for decking or flooring. Besides always tending produce slivers, they will also tend to warp or cup due to the expansion across the depth of the boards.
Rift-sawn boards are probably the least desirable of all the cuts. This is because these cuts can vary quite a bit depending on where in the log they are cut. They also tend to "move" in two directions with makes them poor choices for flooring, table tops and decking. Rift cut is often left for building materials like 2x4, 2x6s, 4x4 and so on. This does not mean that good quality hardwoods are not available in rift-sawn cuts, only that it is often not the ideal cut.
Quarter-sawn is considered by most the ideal cut, and in some ways it is. Quarter-sawn is not as attractive as flat-sawn and is really designed for different building area. Quarter-sawn wood is ideal of table and chair legs, spindles and other long straight pieces. If you are looking for real wooden flooring you will want to lay down quarter sawn (also called edge grain) flooring. It lasts for ever, is quite stable, very strong and does not easily produce slivers.
There is a lot more to learn about wood but this will at least give you a sampling of how woods react and where to use them for more effective and pleasurable projects.
copyright Colin Knecht