A quadrangular indexable drill insert comprising: a substantially flat top surface and bottom surface, a side surface adjoining the top and bottom surfaces (101, 201) to form four sides of the drill insert, the bottom surface is smaller than the top surface to provide positive cutting geometry; four identical cutting edges formed at intersection of the side surface and the top surface, each cutting edge comprising, a first part edge connected to a curved part edge through a nose portion of predetermined radius making a convex curve; a second part edge connected to the first part edge through a transitional edge, said second part edge being tangentially oriented to an imaginary inscribed circle of the insert, wherein said transitional edge makes a concave curve with the first and second part edges (106, 108); a third part edge connected to the second part edge through a transitional edge, wherein said transitional edge is making a convex curve with said second and third part edges (108, 110); and a nose portion of predetermined radius adjoining the third part edge with curved part edge of succeeding cutting edge; a through hole at center of the drill insert extending between the top surface and the bottom surface (101, 201) of the drill insert for mounting the insert with the drill body; and a chamfer provided at bottom edge of the drill insert, characterized in that the curved part edge is a concave curved part edge of predetermined radius and is provided as a corner of the insert. a substantially flat top surface and bottom surface, a side surface adjoining the top and bottom surfaces (101, 201) to form four sides of the drill insert, the bottom surface is smaller than the top surface to provide positive cutting geometry; four identical cutting edges formed at intersection of the side surface and the top surface, each cutting edge comprising, a first part edge connected to a curved part edge through a nose portion of predetermined radius making a convex curve; a second part edge connected to the first part edge through a transitional edge, said second part edge being tangentially oriented to an imaginary inscribed circle of the insert, wherein said transitional edge makes a concave curve with the first and second part edges (106, 108); a third part edge connected to the second part edge through a transitional edge, wherein said transitional edge is making a convex curve with said second and third part edges (108, 110); and a nose portion of predetermined radius adjoining the third part edge with curved part edge of succeeding cutting edge; a first part edge connected to a curved part edge through a nose portion of predetermined radius making a convex curve; a second part edge connected to the first part edge through a transitional edge, said second part edge being tangentially oriented to an imaginary inscribed circle of the insert, wherein said transitional edge makes a concave curve with the first and second part edges (106, 108); a third part edge connected to the second part edge through a transitional edge, wherein said transitional edge is making a convex curve with said second and third part edges (108, 110); and a nose portion of predetermined radius adjoining the third part edge with curved part edge of succeeding cutting edge; a through hole at center of the drill insert extending between the top surface and the bottom surface (101, 201) of the drill insert for mounting the insert with the drill body; and a chamfer provided at bottom edge of the drill insert, characterized in that the curved part edge is a concave curved part edge of predetermined radius and is provided as a corner of the insert.