NEN EN ISO 2320 : 2016

Foreword
1 Scope
2 Normative references
3 Definitions
   3.1 Prevailing torque type nut
   3.2 Prevailing torque developed by a nut
4 Designation system
5 Materials and processes
   5.1 Materials
   5.2 Heat treatment
       5.2.1 Nuts with coarse thread
       5.2.2 Nuts with fine pitch thread
   5.3 Thread
   5.4 Finish
   5.5 Hydrogen embrittlement
6 Mechanical properties
7 Performance requirements
   7.1 Prevailing torque
   7.2 Torque/clamping force
   7.3 Tempering resistance of prevailing torque type nuts
       with non-metallic insert
8 Test methods
   8.1 Proof load test
       8.1.1 Test bolt for proof load test
       8.1.2 Hardened mandrel for proof load tests
   8.2 Hardness test
   8.3 Prevailing torque test
       8.3.1 Test programme
       8.3.2 Torque measuring device
       8.3.3 Clamping force measuring device
       8.3.4 Test bolt for torque testing
       8.3.5 Test washer
9 Marking
Annex A (normative) Recommended testing technique using manual
                    torque wrenches to determine torque
                    performance characteristics of prevailing
                    torque type steel hexagon nuts
Annex B (normative) Tempering resistance test for prevailing
                    torque type nuts with non-metallic insert
Annex C (informative) Torque/clamping force requirements and
                      testing
Annex ZA (normative) Normative references to international
                     publications with their relevant
                     European publications