A crosscut is a cut made into wood that goes perpendicular to the grain of the tree. This term is in contrast to a rip cut that goes parallel to the grain. Crosscuts are the most common method of cutting down trees, as the grain of nearly every tree is perpendicular to the ground. Crosscut saws are a specialized type of human powered saw that have teeth to allow easier cutting against the grain. While the term most often applies to cutting actual trees, any cut made against wood grain during any point of processing is a crosscut.
Most trees grow in spurts, and it is these spurts that result in growth rings and the long fibrous lines within the tree. These lines help give the tree internal structural stability and allow it to flex rather than break. In nearly every case, the fibers go from the base of the tree up toward the sky. This means the tree is stronger when pushed from the side than it is when pushed from above or below. This allows the wood to withstand high winds and momentary impacts without breaking.
These internal features also define the grain of the tree’s wood. When something is with the grain, it runs parallel to the internal structures of the wood. Something that goes against the grain runs perpendicular to those structures. These terms have a more general meaning stemming from the effort it takes to cut the wood. Cuts made with the grain generally require less effort than cuts made against it.
When a tree is cut down, the cut usually goes against the grain and is called a crosscut. In order to remove some of the effort it takes to cut against the grain, people use crosscut saws. These saws have small teeth that have one sharp edge and one less-sharp edge. These teeth typically bend out slightly from the plane of the saw in alternating directions, making the cut area slightly larger than the width of the saw.
When a crosscut saw bites into a tree, it cuts in one primary direction. On most modern saws, this cut is done as the blade moves away from the user. Since the teeth bend out to both sides of the blade, the grain is severed in two spots. The middle part of the wood totally disconnects and becomes sawdust. When the blade moves toward the user, the teeth scoop out leftover dust and pull it from the cut.