Views: 2 Author: Site Editor Publish Time: 2026-02-04 Origin: Site
In industrial manufacturing, steel structures, flange connections and other industrial engineering systems, a seemingly insignificant bolt is often the key to determining the overall safety and reliability of the project. The JIS B 1180 hexagonal bolt standard occupies an important position in many international standard systems for fasteners.
JIS B 1180 is a specialized product standard for hexagonal bolts in Japanese Industrial Standards. It is not only a size specification table, but also a complete technical system covering materials, mechanical properties, dimensional tolerances, thread accuracy, surface treatment, and inspection methods. This standard matches ISO international standards, ensuring the global universality and interchangeability of products, and is an important standard certification for high-quality and high reliability fasteners.
Hexagonal head bolts, named after their hexagonal heads, are one of the most widely used fasteners. Its design advantage lies in:
Powerful tightening torque: The hexagonal head provides sufficient force surface and can be used with universal tools such as wrenches and sockets to apply high pre tightening force.
Good spatial adaptability: The wrench has flexible operating angles and is suitable for narrow or complex installation spaces.
Reliable anti loosening performance: Combined with washers or hexagonal nuts, it can form a stable and firm connection.
The JIS B 1180 standard provides performance and quality assurance for this universal fastener.
According to design, thread and precision, JIS B 1180 standard scientifically classifies hexagonal bolts to meet different scenario requirements:
Nominal diameter type: the most common type, with a stem diameter that is basically the same as the nominal diameter of the thread, strong load-bearing capacity, and extremely high versatility.
Pitch Diameter type: The shaft diameter is reduced to near the thread pitch diameter, achieving lightweight and material savings, suitable for lightweight structures that are sensitive to weight.
Coarse tooth hexagonal bolt: standard selection, fast rotation speed, high tensile strength, easy disassembly and assembly.
Fine tooth hexagonal bolt: With a small pitch, it has better anti loosening and fine adjustment capabilities, and is suitable for connecting thin-walled parts and bearing dynamic loads.
Grade A (Precision): The most stringent dimensional tolerance standard is suitable for high-precision assembly and equipment. Usually for bolts with a diameter ≤ 24mm and a short length.
B-grade (commercial grade): With a conventional tolerance range, it ensures performance while controlling costs, and is the most common type of hexagonal bolt on the market. Bolts that exceed the size range of Grade A are automatically classified as Grade B.
C-grade (loose grade): With a wide tolerance range and low cost, it is mainly used for ordinary connections with low precision requirements.
| Type | Range of nominal diameter d of thread | Corresponding International Standard (informative) | ||
| Designation | Pitch of thread | Product grade | ||
| Nominal diameter hexagon head bolt | Coarse thread | A | d=1.6 mm to 24 mm [nominal length l is up to and including 10d or 150 mm a] | ISO 4014 |
| B | d=1.6 mm to 24 mm [nominal length l is over 10d or 150 mm a] | |||
| d=27 mm to 64 mm | ||||
| C | d=5 mm to 64 mm | ISO 4016 | ||
| Fine pitch thread | A | d=8mm to 24 mm [nominal length l is up to and including 10d or 150 mm a] | ISO 8765 | |
| B | d=8mm to 24 mm [nominal length lis over 10d or 150 mm a] | |||
| d=27 mm to 64 mm | ||||
| Hexagon head screw bolt | Coarse thread | A | d=1.6mm to 24 mm [nominal length lis up to and including 10d or 150 mm a] | ISO 4017 |
| B | d=1.6 mm to 24 mm [nominal length l is over 10d or 150 mm a] | |||
| d=27 mm to 64 mm | ||||
| C | d=5 mm to 64 mm | ISO 4018 | ||
| Fine pitch thread | A | d=8 mm to 24 mm [nominal length l is up to and including 10d or 150 mm a] | ISO 8676 | |
| B | d=8mm to 24 mm [nominal length lis over 10d or 150 mm a] | |||
| d=27 mm to 64 mm | ||||
| Pitch diameter hexagon head bolt | Coarse thread | B | d=3 mm to 20 mm | ISO 4015 |
| Note a) Whichever is the shorter. | ||||
When selecting JIS B 1180 bolts, the following specifications must be clearly defined, which together constitute the complete product identification:
Standard number: JIS B 1180
Thread specifications: such as M16 (coarse thread) or M16 × 1.5 (fine thread, 1.5 is pitch)
Length: The nominal length of the screw, such as 70L.
Performance level: This is the strength core.
Steel bolts: commonly used 4.8 (low carbon steel, low strength), 8.8 (medium high strength), 9.8 (high strength, coarse tooth characteristic), 10.9 (extremely high strength). The numbers represent the ratio of tensile strength to yield strength.
Stainless steel bolts: such as A2-70 (austenitic stainless steel, tensile strength 700MPa).
Product grade: A, B, or C.
Surface treatment: such as hot-dip galvanizing, electroplating galvanizing, Dacromet, etc., additional clear standards and thickness are required.
Complete example: JIS B 1180 hexagonal bolt M20 x 80L 8.8 B-grade hot-dip galvanized.
Reliable quality and rigorous system: Strictly following JIS standards, there is a complete set of testing specifications (such as JIS B 1099 general requirements) from raw materials to finished products to ensure stable performance of each batch of products.
Clear classification and rich selection: Clear performance level identification allows engineers to accurately calculate and select, with corresponding values for everything from ordinary fixed to critical load-bearing.
Precision grading, economic efficiency: A/B/C three-level tolerance system allows users to find a balance between precision and cost, avoiding excessive or insufficient quality.
Universal standards, strong interchangeability: Corresponding to ISO standards, convenient for equipment export, maintenance, and spare parts replacement.
Strong weather resistance (combined with surface treatment): Through surface treatment such as hot-dip galvanizing, it can provide decades of anti-corrosion protection, especially suitable for outdoor, humid or corrosive environments.
Heavy industry: construction machinery, mining equipment, port cranes, pressure vessels.
Steel structure buildings: factories, bridges, sports venues, transmission towers.
Automotive and Transportation: Commercial Vehicle Chassis, Rail Vehicle Components, Automotive Molds.
High end equipment: semiconductor manufacturing equipment, printing machinery, injection molding machines.
Energy and electricity: wind turbines, thermal power station equipment, transmission and transformation facilities.
Ship ocean: Ship deck machinery, ocean platform modules.
Do not confuse grades: specify whether the requirement is grade A (precision) or grade B (universal), and grade C or medium diameter bolts cannot be used for critical load-bearing structures.
Surface treatment needs to be clear: especially for hot-dip galvanizing, it is necessary to specify the standard (such as JIS H 8641), the minimum local thickness of the coating, and whether dehydrogenation treatment is required in the contract (which is crucial for high-strength bolts above grade 8.8 to prevent hydrogen embrittlement and fracture).
Matching use: JIS B 1181 hex nuts of the same grade and material should be used to ensure that the connection performance matches.
Apply torque correctly: The friction coefficient of coated bolts varies, so it is necessary to tighten them according to the "post plating" torque value and use a torque wrench to ensure accurate pre tightening force.
Legitimate procurement channels: Choose legitimate suppliers who can provide material reports, heat treatment records, and coating testing reports to ensure traceability.
JIS B 1180 hex bolts are not just a product, but also represent a rigorous, reliable, and efficient industrial connection solution. A deep understanding of its standard system and classification can help engineers, procurement personnel, and decision-makers choose suitable products from numerous standard sizes, optimize costs while ensuring structural safety and lifespan, and lay a solid and reliable "foundation" for your projects and products.
