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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 M8×1 to M39×3 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.