The most common method of sawing logs into lumber is what is called plain sawing, or slash sawing. This is really a matter of slicing the log into the required sizes, as shown in the following illustration:

Plain Sawing

Effect Of Warping

This is the most economical way of sawing logs, for it gives the greatest possible amount of lumber with the least waste. There are, however, some disadvantages in this method of sawing, particularly if the lumber is to be used for fine cabinet work. Plain sawed lumber usually warps very badly. If you are to understand why this is true, you will need to know something about the cause and effect of warping of lumber.

In a living tree there is always considerable moisture in the form of sap. When the tree is cut down the sap, of course, ceases to circulate, and the moisture in the log begins to evaporate. As the log dries, all of the concentric rings, representing the annual growths, become a little shorter and thus cause the log to crack. If it has been sawed into boards it will, of course, dry even more rapidly, causing the portion of the rings in each board to shorten considerably, and thus bend or warp the board, as shown in the illustration. You will observe that the edges of the board warp from the heart of the log, and you can readily understand why this is true if you will stop to consider the cause of the warping. You will notice that the plank in the central portion of the log does not bend, but the shortening of the rings causes it to become thinner on each edge.