Multifunctional nut

The utility model discloses a multifunctional nut which comprises a head part, a screw rod part and a convex navel part which are integrally formed in sequence, wherein the head part is provided with an upper counter bore, and the upper counter bore is a polygonal counter bore; the lower end surface of the head part is also convexly provided with a sealing convex part; the screw rod part is provided with an internal thread hole and is also provided with an external thread; a sinking hole is formed in the convex navel part; the peripheral wall of the lower sinking hole is bent inwards, and a gasket mounting groove is formed in the lower sinking hole, so that the sealing gasket is tightly pressed in the gasket mounting groove; or the peripheral wall of the sunken hole is bent outwards to form a buckling part outside the sunken hole so as to buckle the metal plate. The multifunctional nut can bear large tightening force, is not prone to being damaged by screwing and is easy to machine. The self-tapping screw is