The ornamental design for a coffeegrinder, as shown and described.
FIG. 1 is a front isometric view of a coffee grinder showing the new design.
FIG. 2 is a first side view thereof.
FIG. 3 is a second side view thereof.
FIG. 4 is a rear elevation view thereof.
FIG. 5 is a front elevation view thereof.
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The shade lines in the Figures show contour and not surface ornamentation. The broken lines in the Figures depict portions of the coffee grinder that form no part of the claimed design.