The ornamental design for a handtoolstem, as shown and described.
FIG. 1 is a perspective view of a hand tool stem, showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a perspective view showing an embodiment of the claimed design, wherein the broken lines are shown for illustrative purposes only and form no part of the claimed design.