Bolt Database & Calculator
ISO metric bolt database (M6–M48) with grades 4.6, 8.8, 10.9, 12.9 — plus tensile, shear, torque and bolt-group calculators.
Calculator Sections
| Size | Grade | Std | d (mm) | Pitch (mm) | As (mm²) | Anom (mm²) | fub (MPa) | fyb (MPa) | Ft,Rd (kN) | Fv,Rd (kN) |
|---|
Ft,Rd = 0.9 × fub × As / γM2 (γM2=1.25, EN 1993-1-8). Fv,Rd = 0.6 × fub × As / γM2 (single shear, threads in shear plane). Reference only — verify against project-specific code requirements.
EN 1993-1-8 Table 3.4 — Design preload Fp,C = 0.7 × fub × As
| Size | Grade 8.8 Fp,C (kN) | Grade 10.9 Fp,C (kN) |
|---|
EN 1993-1-8 Table 3.3 minimum distances
| Dimension | EN 1993-1-8 | For M20 |
|---|---|---|
| End dist. e1 | ≥ 1.2 d0 | ≥ 26.4 mm |
| Edge dist. e2 | ≥ 1.2 d0 | ≥ 26.4 mm |
| Bolt pitch p1 | ≥ 2.2 d0 | ≥ 48.4 mm |
| Bolt spacing p2 | ≥ 2.4 d0 | ≥ 52.8 mm |
| Max pitch (inner) | ≤ min(14t, 200) mm | — |
| Max end dist. | ≤ 4t + 40 mm | — |
d0 = hole diameter = d + 2mm (M12–M14) or d + 3mm (M16+). t = plate thickness.
How Bolt Capacity is Calculated — EN 1993-1-8
Structural bolt design capacities on this platform are calculated in accordance with EN 1993-1-8:2005 (Eurocode 3 — Design of joints) and ASTM bolt standards for American-grade fasteners. The two primary failure modes checked for any bolt in a structural connection are shear (single or double shear) and tension (direct pull-out or combined with shear).
Shear Design Resistance
For a single bolt in shear, the design shear resistance per shear plane is given by:
Fv,Rd = (αv × fub × A) / (γM2)
Where αv is 0.6 for bolt grades 4.6, 8.8 and 10.9 (shear through the shank), fub is the ultimate tensile strength of the bolt (MPa), A is the gross cross-sectional area of the bolt shank (mm²), and γM2 is the partial factor for bolt resistance (typically 1.25 per EN 1993-1-8). For bolts where the shear plane passes through the threaded portion, the tensile stress area As is used in place of the gross area.
Tension Design Resistance
The design tension resistance of a bolt is:
Ft,Rd = (0.9 × fub × As) / γM2
Where As is the tensile stress area of the bolt thread. When a bolt is subject to combined shear and tension, the interaction criterion per EN 1993-1-8 clause 3.7 must be satisfied: (Fv,Ed / Fv,Rd) + (Ft,Ed / 1.4 Ft,Rd) ≤ 1.0.
Bolt Grades and Mechanical Properties
ISO metric bolt grades are designated by two numbers (e.g. 8.8, 10.9) representing yield-to-ultimate ratios and ultimate strength. The commonly used structural grades are:
- Grade 4.6: fy = 240 MPa, fub = 400 MPa — used in light structural connections and secondary members
- Grade 8.8: fy = 640 MPa, fub = 800 MPa — the standard grade for structural steelwork connections per Eurocode 3
- Grade 10.9: fy = 900 MPa, fub = 1000 MPa — high-strength bolts used in preloaded (friction-grip) connections and heavily loaded joints
- Grade 12.9: fy = 1080 MPa, fub = 1200 MPa — very high strength, used in machine-critical connections; not typically used in structural steelwork
- ASTM A325: fub ≈ 830 MPa — equivalent to Grade 8.8 for AISC/LRFD designs
- ASTM A490: fub ≈ 1040 MPa — equivalent to Grade 10.9, used in high-strength preloaded connections per AISC
- ASTM A193 B7 (stud bolts): fub = 862 MPa — used in ARAMCO (SAES-L-109) flange connections and pressure vessel bolting
Bearing Resistance and Edge Distance
In addition to bolt shear and tension capacity, the bearing resistance of the connected plate at each bolt hole must be checked. Per EN 1993-1-8, the design bearing resistance is:
Fb,Rd = (k1 × αb × fu × d × t) / γM2
Where d is the nominal bolt diameter, t is the plate thickness, fu is the ultimate tensile strength of the plate, and k1 and αb are factors that account for edge distance and bolt pitch. Minimum edge distances and spacing requirements (e1, e2, p1, p2) are specified in EN 1993-1-8 Table 3.3. Always check bearing capacity against bolt shear capacity and take the minimum as governing.
GCC Project Notes — SAES and ARAMCO Bolting
For Saudi Aramco projects, bolt specifications are governed by SAES-L-109 for piping flanges and SAES-Q-007 for structural connections. ARAMCO typically specifies ASTM A193 Grade B7 studs with A194 Grade 2H heavy hex nuts for high-temperature and pressure service. Torque values must be applied per ASME PCC-1 guidelines. For structural steelwork in GCC projects under SBC 303, AISC LRFD bolt capacities and edge distance requirements apply.