The ornamental design for a gripdetail for a power tool, as shown and described.
FIG. 1 is a perspective top front view of an embodiment of a grip detail for a power tool with an attached foot plate and tool handle, showing my new design;
FIG. 2 is a front view of an embodiment of the grip detail for a power tool;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof; and,
FIG. 5 is a right side view thereof.
The broken lines in the drawings depict environmental subject matter only and form no part of the claimed design.