The ornamental design for a tool for cleaning the outer surface of a tube, as shown and described.
FIG. 1 is a perspective view of a tool for cleaning the outer surface of a tube showing my new design.
FIG. 2 is a right-side elevational view thereof. The left-side elevational view, the top plan view and the bottom plan view being a mirror images thereof;
FIG. 3 is a cross-sectional view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a rear elevational view thereof; and,
FIG. 6 is a side elevational view showing the tool inserted into an electric drill. The drill is shown in broken lines for illustrative purposes only and forms no part of the claimed design.