I claim the ornamental design for a drill hammer, as shown and described.
FIG. 1 is a bottom view of the drill hammer.
FIG. 2 is a side perspective view of the drill hammer.
FIG. 3 is a view of a first side of the drill hammer.
FIG. 4 is a front view of the drill hammer.
FIG. 5 is a view of a second side of the drill hammer.
FIG. 6 is a rear view of the drill hammer; and,
FIG. 7 is a top view of the drill hammer. Any broken lines showing the environment in FIGS. 1-7 are for illustrative purposes only and form no part of the claimed design.