Serrated flange nuts are hex nuts with non-spinning washers attached at the bottom. Underneath the washers are serrations which allow the nuts to securely fasten when vibrations are present and prevent them from being used with washers or on surfaces that can be scratched.
We carry serrated flange nuts in metric and inch. We also offer them case harden, grade 5, grade 8, and large flange diameter. KD Fasteners carries them stock in zinc, zinc/yellow, black phosphate, and also in 18-8 stainless steel. We can also supply them in different styles of plating.