The ornamental design for a drillchuck, as shown and described.
FIG. 1 is a front view of a drill chuck showing my new design;
FIG. 2 is a right side view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is bottom view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a first perspective view thereof; and,
FIG. 8 is a second perspective view thereof.
The broken line showing of the drill chuck is included for the purpose of illustrating portions of the drill chuck and forms no part of the claimed design.