A method for locking a nut with an inner thread, in which the ultimate tensile strength (Rm) and yield strength (Re) of the material constituting the nut are determined according to temperature. An optimal heating temperature is determined, at which a maximum of a relative plastic interval of the material is reached, said relative plastic interval being defined by the formula (Rm−Re)/Rm, and a maximum heating time is determined, above which the nut presents the risk of deterioration of its microstructure and/or of its initial mechanical strength. The nut is heated to a temperature substantially equal to said optimal temperature and for a heating time of less than said maximum time so that the initial microstructure and mechanical strength of the material constituting the nut are preserved, and a body of the nut is deformed locally by bending.