The ornamental design for a frontgrill for tractors, as shown and described.
1. Front grill for tractors
1.1 : Perspective
1.2 : Front
1.3 : Back
1.4 : Top
1.5 : Bottom
1.6 : Right
1.7 : Left
1.8 : Partial Enlarged view
1.9 : Referential view showing state of use
1.10 : Referential view showing state of use
The broken lines shown in the drawings are for illustrative purpose only and form no part of the claimed design; the dash-dot lines show the boundaries between the parts seeking the protection and the other parts; the small circles covering the bottom two-thirds of the article show the part is perforated. The small circles are abbreviated in FIGS. 1.9 and 1.10 using a dotted pattern to show the outline of the article clearly.