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IS 12431:2018 is the Indian Standard (BIS) for hexagon socket head cap screws. 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.
! 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.
ISO 4762:2004International Organization for Standardization (ISO), Switzerland
HighCurrent
Hexagon socket head cap screws
IS 12431:2018 is a technical equivalent of this standard, covering identical dimensions, materials, and properties.
DIN EN ISO 4762:2004Deutsches Institut für Normung (DIN), Germany
HighCurrent
Hexagon socket head cap screws (ISO 4762:2004)
The German national adoption of ISO 4762, making it identical in technical content to the IS code.
ASME B18.3-2018American Society of Mechanical Engineers (ASME), USA
MediumCurrent
Socket Cap, Shoulder, Set Screws, and Hex Keys (Inch and Metric Series)
Covers metric hexagon socket head cap screws but with some different dimensional tolerances, material callouts, and a wider size range.
JIS B 1176:2017Japanese Industrial Standards (JIS), Japan
HighCurrent
Hexagon socket head cap screws
Specifies the same product type with dimensions and properties that are largely harmonized with ISO 4762.
Key Differences
≠While IS 12431 specifies property classes (e.g., 8.8, 10.9, 12.9) per IS 1367-3/ISO 898-1, the equivalent ASME B18.3 standard references US-specific ASTM material standards like ASTM A574 for alloy steel screws.
≠IS 12431 specifies a default thread tolerance class of 6g. ASME B18.3 specifies 4g6g as its standard for metric screws, which offers a tighter fit, although 6g is also permissible.
≠There are minor differences in dimensional tolerances for features like head diameter (dk), head height (k), and socket depth (t) between the IS/ISO standards and ASME B18.3.
≠The standard size range covered by IS 12431 (and ISO 4762) is from M1.6 to M64, whereas the metric series in ASME B18.3 extends to M100.
Key Similarities
≈The fundamental geometry of a cylindrical head with an internal hexagonal drive and a threaded shank is consistent across all equivalent standards.
≈All major international standards for metric screws, including IS 12431, utilize the standard ISO metric thread profile (as per ISO 68-1), ensuring thread interchangeability.
≈The use of numerical Property Classes (e.g., 12.9) to denote mechanical strength (tensile strength, hardness, etc.) is a harmonized concept between IS 12431 and ISO 4762.
≈The marking of high-strength screws with the manufacturer's identification and the property class on the head is a common requirement for traceability and safety.
Parameter Comparison
Parameter
IS Value
International
Source
Governing standard for Mechanical Properties
IS 1367 (Part 3) / ISO 898-1
ASTM A574/A574M
ASME B18.3-2018
Standard Thread Tolerance
6g
4g6g
ASME B18.3-2018
Head Diameter (dk) for M10 screw
15.67 mm (min) / 16.00 mm (max)
15.73 mm (min) / 16.00 mm (max)
ASME B18.3-2018
Head Height (k) for M10 screw
9.82 mm (min) / 10.18 mm (max)
9.78 mm (min) / 10.00 mm (max)
ASME B18.3-2018
Socket Size Across Flats (s) for M10
8.025 mm (min) / 8.175 mm (max)
8.020 mm (min) / 8.120 mm (max)
ASME B18.3-2018
Minimum Socket Depth (t) for M10
5.0 mm
5.0 mm
ASME B18.3-2018
Thread Length (b) for M10 x 80 screw
32 mm (nominal)
32 mm (nominal)
ASME B18.3-2018
⚠ Verify details from original standards before use
Key Values6
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
Tables & Referenced Sections
Key Tables
Table 1 - Dimensions of hexagon socket head cap screws
Table 2 - Mechanical properties of hexagon socket head cap screws
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).