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IS 2155:1982 is the Indian Standard (BIS) for black bolts, nuts and lock nuts (diameter 6 to 39 mm). This standard specifies the dimensions, mechanical properties, and material requirements for black bolts, nuts, and lock nuts in the diameter range of 6 mm to 39 mm. It is widely used in the fabrication and erection of light structural steelwork and general engineering applications.
Specifies requirements for black hexagon head bolts, nuts and lock nuts of diameters 6 to 39 mm.
Overview
Status
Current
Usage level
Frequently Used
Domain
Structural Engineering — Fasteners, Bolts and Anchors
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Black bolts (also known as ordinary or rough bolts) have larger hole clearances and tolerances compared to precision or high-strength bolts.
! They are strictly recommended for static loads and secondary connections, and should be avoided in structures subjected to vibrations, impact, or fatigue.
! Always ensure that the property class of the nut matches or exceeds the property class of the corresponding bolt to prevent thread stripping.
Covers dimensional and tolerance requirements for general-purpose, unfinished (black) hexagon head bolts.
ASTM A307-21ASTM (US)
HighCurrent
Standard Specification for Carbon Steel Bolts, Studs, and Threaded Rod, 60 000 PSI Tensile Strength
Specifies Grade A bolts for general purpose applications, which are the direct US equivalent of 'black bolts'.
ISO 898-1:2013ISO (International)
MediumCurrent
Mechanical properties of fasteners made of carbon steel and alloy steel — Part 1: Bolts, screws and studs with specified property classes
Defines the mechanical property classes (e.g., 4.6) that are referenced by product standards for bolts.
DIN 555DIN (Germany)
HighWithdrawn
Hexagon bolts; product class C
Was the historical German standard for 'black' bolts before harmonization with ISO standards.
Key Differences
≠IS 2155 specifies a single grade of bolt, whereas international systems like ISO 898-1 define a range of property classes (e.g., 4.6, 5.6, 8.8, 10.9) offering greater design flexibility.
≠IS 2155 is an omnibus standard covering bolts, nuts, and lock nuts in one document. Modern international practice separates these into distinct standards (e.g., ISO 4016 for bolts, ISO 4034 for nuts).
≠Dimensional tolerances in IS 2155:1982 are generally wider and based on older manufacturing practices compared to the more refined 'Product Grade C' tolerances in the current ISO 4016.
≠IS 2155 explicitly covers lock nuts, whereas the direct international equivalents for general-purpose bolts (like ASTM A307 or ISO 4016) do not; lock nuts are covered by separate specialized standards (e.g., ISO 7040).
Key Similarities
≈The specified minimum tensile strength of 400 MPa in IS 2155 is directly comparable to ISO Property Class 4.6 bolts (400 MPa) and ASTM A307 Grade A bolts (approx. 414 MPa).
≈All standards are intended for similar applications: general-purpose, non-critical assemblies, and connections not requiring pre-loading or high-strength properties.
≈The fundamental material requirement is for low-to-medium carbon steel, with bolts typically supplied in an 'as-forged' or 'black' finish.
≈The basic geometry of the fasteners (hexagon head for bolts, hexagon shape for nuts) and the use of standard metric threads (as per ISO) are consistent across the standards.
Parameter Comparison
Parameter
IS Value
International
Source
Bolt Tensile Strength
400 - 550 MPa
≥ 400 MPa (Nominal)
ISO 898-1 (Class 4.6)
Bolt Yield Strength (Minimum)
Not explicitly stated for bolts (implied ~240 MPa from material spec)
240 MPa
ISO 898-1 (Class 4.6)
Bolt Tensile Strength Range (Alternate)
400 - 550 MPa
414 - 690 MPa (60 - 100 ksi)
ASTM A307 (Grade A)
Nut Proof Load (M16 Nut)
93.6 kN
99.2 kN
ASTM A563 (Grade A)
Product Tolerance Grade
Corresponds to a coarse grade
Product Grade C
ISO 4016:2000
Governing Thread Standard
IS 4218 (ISO metric screw threads)
ISO 261 / ISO 965 (ISO general purpose metric screw threads)
ISO 4016 / ISO 898-1
Material Specification Basis
Reference to a general structural steel standard (IS 226, now IS 2062)
Specific chemical composition limits within the fastener standard
ASTM A307-21
⚠ Verify details from original standards before use