This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
The arrangement of the fibers which go to make up a piece of timber give to it certain characteristics which are described as different conditions of the "grain" of the wood, the word "grain" being used as a substitute for the word fiber. Thus "across the grain," means at right angles to the general direction of the fibers; "along the grain," means parallel to the direction of the fibers. In like manner woods are said to be "fine grained," "coarse grained," "cross grained," or "straight grained," these terms being used to indicate the relation of the fibers to each other and to the general direction of the growth of the tree. The wood is said to be fine grained when the annual rings are relatively narrow so as to show a large number of fine lines on a cross section of the log, and it is said to be coarse grained when the rings are wider so as to show a smaller number of coarser lines on the cross section of the log. Woods which are fine grained are generally harder and denser than those which are coarse grained and they can be made to take a high polish, while with the others, as a rule, this is not possible. Fine-grained woods arc also said to be close grained. When the fibers are straight and parallel to the direction of the trunk of the tree, the wood is said to be straight grained, but if they are twisted so as to be spiral in form, not growing straight but following around the trunk of the tree, the wood is said to be cross grained. In Fig. 3, are shown three pieces of timber of which A is absolutely cross grained, B is partially cross grained, and C is straight grained. As examples, it may be mentioned that hemlock is coarse grained and usually cross grained, while white pine is close grained, although soft, and is usually straight grained. Most of the hard woods are fine grained.
Fig. 2. Diagram of Pine Wood Fibers Magnified.