This standard establishes the dimensions called key widths of hexagonal products, for example, hex head screws, hex nuts, hex screws and flange nuts, to be used in the relevant product standards. It also establishes a rational relationship between the support area under the head (or under the nut) (which determines the extent of the average compressive stress in the support area on the connected pieces in relation to the clamping force applied to the fastening element ) and the resistant section of the screw (which reacts to the tightening force that can be applied for a given strength class, to the fastener). This technical calculation method was applied to each of the hexagonal series to obtain a rational progression of the support area/resistant sections ratios suitable for industrial applications.
UNI 5625-1986 history
1986UNI 5625-1986 Fixture components. Hexagonal products. Width on wrench
1965UNI 5625-1965 Screws and hexagonal nuts. Wrench width. Nail head height and nut standard height