The broadaxe, with a large, heavy head, was never used to fell trees. Often it (like this one) had a head that was beveled on just one side and was flat on the other. The handle was bent or offset. (Sometimes the handle could be inserted from either side to make the axe left- or right-handed.) In use, a log was held down with dogs (iron bars, bent and sharpened like large staples), and a straight line marked out. Then the hewer would stand on the log and "score" the log with a normal ax (like the double-bit shown). Then, standing beside the tree, he'd use the broadaxe to split off the extra wood between the scores, thus, "hewing to the line". After hewing one side, the log was turned and hewed again, and the process repeated until a rectangular timber resulted. Many logging necessities were made this way -- from timbers for diving dams to the "Deacon's seat" that ran the length of logging camps.
Larger broadaxes, often beveled on both sides, were used by the "tie hacks", who would drop a tree with a felling axe, then walk up and down it, hewing as they went. By this method a tie hack could produce 30-60 railroad ties a day.
And even larger broadaxes were used to "square" (actually make polygonal before shipping) the huge old pines that were so important as masts for King George's Navy.