ISO 2320:2015

ISO 2320:2015 specifies the functional properties for prevailing torque steel nuts when tested at an ambient temperature range of +10 °C to +35 °C. It includes a combined test method to determine the prevailing torque properties and the torque/clamp force properties at the same time.
It applies to prevailing torque all metal type nuts and prevailing torque non-metallic insert type nuts:
-      with triangular ISO thread in accordance with ISO 68-1;
-      with diameter/pitch combination in accordance with ISO 261 and ISO 262;
-      with coarse pitch thread M5 to M39 or with fine pitch thread M8 × 1 to M39 × 3;
-      with thread tolerances in accordance with ISO 965-2;
-      with mechanical properties in accordance with ISO 898-2;
Prevailing torque values specified in this standard are based on laboratory test conditions.
NOTE 1       Actual prevailing torques in practical application can vary.
NOTE 2       All metal type nuts conforming to the requirements of this International Standard are used in applications ranging from -50 °C to +150 °C.
NOTE 3       Non-metallic insert type nuts conforming to the requirements of this International Standard are used in applications ranging from -50 °C to +120 °C.
WARNING - Temperatures outside the ambient temperature range can influence the functional properties (torque/clamp force and prevailing torque properties), see Annex A.