Example and table with designation. Material: steel for classes oa and 4d, according to UNI 3740-65, or other material that must be indicated in the designation instead of the class.
UNI 6425-1969 history
1969UNI 6425-1969 Cup square screws and bolts with square nut for manufacture of railway and tramway rolling stock. ISO metric coarse thread. Finish c.