What is the differences between an ax and a hatchet? Is it the length of the handle? Is it the size of the tools head? No! The differences is actually the shape of the tool. Take a close look at this picture. On the right you see four axes, the smallest has maybe an 18 inch handle and weighs around a pound. Yet its still an ax.
On the left side there is a tomahawk, with the tan wooded handle, which has a very distinctive shape – almost like a flat funnel. On top of the tomahawk with the red handle is the hatchet. Notice how the blade part is wider, then there is the big “V” on top and bottom of the head, also notice the butt of the tool is fatter and wider when compared to the ax.
Hatchets were often used in frontier settings as a tool that could be used for a number of chores around the home. A hatchet is ideal for splitting sections of kindling into smaller sections, as well as cutting through small sections of wood, such as a young tree. In a time when many people hunted and killed game for use at the dinner table, the hatchet was also a great tool to use in cutting through the bone or cartilage of a deer carcass. Even with domestic animals, the hatchet would be just the right size to use in severing the heads from chickens, or as part of the tools that would be used to butcher a hog.
Along with use around the home, a hatchet has also been used as a weapon. Because the tool can be wielded with one hand, it is possible to use the hatchet with the same dexterity of a knife. The hatchet is common part of camping gear, simply because it is compact, and it provides both uses that are utilitarian in nature and also provides an element of protection in the wild.
Taken from http://en.wikipedia.org/wiki/Axe
The axe, or ax, is an implement that has been used for millennia to shape, split and cut wood, harvest timber, as a weapon and a ceremonial or heraldic symbol
So please all do me a favor and stop calling hand axes, hatchets. It is not the size of the tool, but the shape of its head that makes all the differences.