What are the standard property classes covered in IS 12431?

The standard covers property classes 8.8, 10.9, and 12.9 (Clause 5, Table 2).

How do I correctly designate a screw for ordering?

Designate by name, IS number, thread size, nominal length, and property class. Example: 'Hexagon socket head cap screw IS 12431 M10 × 50 - 12.9' (Clause 8).

What is the Allen key (socket wrench) size for an M8 screw?

The nominal size across flats (s) is 6 mm, as specified in Table 1.

What is the material for a Class 12.9 screw?

Alloy steel, quenched and tempered, with chemical composition and mechanical properties as specified in IS/ISO 898-1 (Clause 5.1).

IS 12431

: 2018

Hexagon socket head cap screws

CurrentFrequently UsedSpecificationGeneral · Fasteners, Bolts and Anchors

Archive.org BIS Portal Google

This standard specifies the characteristics of hexagon socket head cap screws with metric threads from M1.6 up to and including M64. It defines their dimensions, tolerances, materials, mechanical properties for property classes 8.8, 10.9 and 12.9, and designation system. This standard is the Indian adoption of the international standard ISO 4762:2004.

Specifies characteristics of hexagon socket head cap screws with product grade A and threads from M1.6 up to M64.

Quick Reference Values

Minimum tensile strength (Class 12.9)1220 MPa

Minimum tensile strength (Class 8.8)800 MPa

Hardness Range (Class 12.9)385 to 440 HV

Socket size across flats (s) for M10 screw8 mm

Head diameter (dk) for M10 screw16 mm

Head height (k) for M10 screw10 mm

Practical Notes

Always specify the property class (e.g., 8.8, 10.9, 12.9) on drawings and purchase orders as it is critical for the screw's strength and application suitability.

This standard is technically equivalent to ISO 4762, which allows for interchangeability with globally sourced components.

Check for proper marking on the screw head, which should include the property class and manufacturer's identification mark, to ensure compliance.