ISO 2320:2008 specifies the mechanical and performance properties for prevailing torque type steel nuts when tested at an ambient temperature range of +10 °C to +35 °C. It includes a single test to determine the prevailing torque properties (performance properties) and/or the torque/clamp force properties.ISO 2320:2008 applies to prevailing torque all metal type nuts and prevailing torque non-metallic insert type nuts: a) with triangular ISO thread according to ISO 68-1; b) with diameter/pitch combination according to ISO 261 and ISO 262; c) with coarse pitch thread M3 to M39 and mechanical properties according to ISO 898-2; d) with fine pitch thread M8x1 to M39x3 and mechanical properties according to ISO 898-6; e) within the temperature range of -50 °C to +150 °C for prevailing torque all metal type nuts; f) within the temperature range of -50 °C to +120 °C for prevailing torque non-metallic insert type nuts.ISO 2320:2008 does not apply: 1) to nuts of type e), outside the range -50 °C to +150 °C for prevailing torque all metal type nuts, when it is necessary to consult an experienced fastener materials expert to determine appropriate choices for a given application; 2) to nuts of type f), when use at or near the temperature limits can reduce the prevailing torque capability of prevailing torque non-metallic insert type nuts and can require the use of an adequate non-metallic material — it is necessary to consult an experienced fastener materials expert for temperatures outside the range -50 °C to +120 °C for prevailing torque non-metallic insert type nuts to determine appropriate choices for a given application.