We claim the ornamental design for a brush axe, as shown and described.
FIG. 1 is a front top perspective view of the claimed design;
FIG. 2 is a rear bottom perspective view of the claimed design of FIG. 1;
FIG. 3 is a front elevation view of the claimed design of FIG. 1;
FIG. 4 is a rear elevation view of the claimed design of FIG. 1;
FIG. 5 is a right side view of the claimed design of FIG. 1;
FIG. 6 is a left side view of the claimed design of FIG. 1; and,
FIG. 7 is a top view of the claimed design of FIG. 1.
The ornamental design which is claimed is shown in solid lines in the drawings. The broken lines in the drawings are for illustrative purposes only and form no part of the claimed design.