SBAC TS 149 Issue 2 (2004) Technical Specification For All Metal Self Locking Nuts (unj Threads), 1550 Mpa (225,000 Lbf/in[2]) Minimum Tensile Strength At Ambient Temperature Gives the requirements for all metal self-locking nuts, plate nuts and shank nuts made of heat resisting nickel base alloy which will develop a minimum tensile strength of 1550 MPa (225,000 lbf/in[2])