The ornamental design for a grindingtip for grinder, as shown and described.
FIG. 1 is a bottom view of the grinding tip for grinder;
FIG. 2 is a front view of the grinding tip for grinder;
FIG. 3 is a top view of the grinding tip for grinder;
FIG. 4 is a left side view of the grinding tip for grinder;
FIG. 5 is a perspective view of the grinding tip for grinder;
FIG. 6 is a rear view of the grinding tip for grinder;
FIG. 7 is a reference view of the grinding tip for grinder; and,
FIG. 8 is a right side view of the grinding tip for grinder.
The broken line showing of the grinding tip for grinder; in FIG. 7 is included for the purpose of illustrating environment and forms no part of the claimed design.