What are the property classes covered by this standard?

Property classes 5, 8, 10, and 12 are specified (Clause 5.1 and Table 2).

Is lubrication allowed during the prevailing torque test?

No, the test must be conducted on nuts in the 'as-received' condition without any added lubrication (Clause 7.2.1).

What is the specified thread type?

The nuts use ISO metric coarse pitch screw threads with a tolerance class of 6H as per IS 4218 (Part 2) (Clause 6).

How should these nuts be marked?

Nuts must be marked with the manufacturer's identification and the property class symbol, as per IS 1367 (Part 6) (Clause 9).

IS 12474

: 1994

Hexagon prevailing torque type all-metal nuts

CurrentSpecializedSpecificationMaterials Science · Fasteners, Bolts and Anchors

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This standard specifies the dimensions, material properties, and performance requirements for hexagon prevailing torque type all-metal nuts. It covers property classes 5, 8, 10, and 12, detailing mechanical characteristics like proof load, hardness, and the essential prevailing torque values that provide resistance to loosening under vibration.

Specifies characteristics of hexagon prevailing torque type all-metal nuts with threads from M5 up to M39.

Quick Reference Values

Proof Load Stress (Property Class 8)800 MPa

Proof Load Stress (Property Class 10)1000 MPa

Thread Tolerance Class6H

Maximum Test Temperature for Torque250 °C

Vickers Hardness (Property Class 8)180 to 302 HV

Vickers Hardness (Property Class 10)272 to 353 HV

Practical Notes

The 'all-metal' designation means the locking feature is created by deforming the nut's threads, not by using a non-metallic insert like nylon. This makes them suitable for higher temperature applications.

These nuts are generally intended for single-use, as their prevailing torque performance may degrade upon removal and re-tightening.

Ensure the property class of the nut (e.g., Class 10) is compatible with the property class of the mating bolt (e.g., Class 10.9) to prevent thread stripping.