SYZ ENGINEERING PRELIMINARY DESIGN TOOL · REFERENCE-BASED ESTIMATE
Bolt Double-Shear Load Capacity Calculator
Estimate the shear failure load of a bolt in double shear — the standard clevis configuration where a bolt passes through a rod end bore between two bracket ears.
FASTENER SHEAR STRENGTH · ASME B18.2.1 DIMENSIONS
Bolt Double-Shear Load Capacity
Estimates the shear failure load of a bolt in double shear — the standard clevis configuration where a bolt passes through a rod end bore between two bracket ears.
[Inches]
Assumes the unthreaded shank spans both shear planes — good clevis design practice keeps threads out of the shear plane.
τ ≈ 0.6 × UTS
[lbf]
SYZ Guideline
Estimated Double-Shear Capacity
35,343 lbf
Single-shear capacity (one plane): 17,671 lbf
✔
Sf = 2.01 : 1 — adequate margin by SYZ guideline (Sf ≥ 2.0).
Engineering Model (approximation, not a certified shear rating)
Standard Reference
Bolt nominal diameters follow ASME B18.2.1. Shear strength ≈ 0.6 × ultimate tensile strength is a widely used engineering approximation, not a codified single value — for certified shear strength, consult ASTM F606 fastener test data or the manufacturer’s published shear rating.
Calculation Method
A = π/4·D² · Double Shear = 2 × A × τ · Sf = Capacity / (P × Kd)
Assumptions & Limitations
- Assumes the bolt shank (not threads) spans both shear planes — verify your grip length keeps threads out of the joint.
- τ≈0.6×UTS is a common approximation, not a guaranteed value — actual shear strength varies by manufacturing process and material lot.
- Does not check bearing/tear-out failure of the bracket or rod end material around the bolt hole — a separate failure mode that can govern before the bolt itself shears.
- Does not model fatigue, preload, or clamping friction contribution to joint capacity.
STATIC REFERENCE DATA
Reference: Double-Shear Capacity by Bolt Size & Grade
Precomputed values from the exact formula used above — useful as a quick lookup without re-entering inputs.
| Bolt Size | Grade 5 (~120ksi) | Grade 8 (~150ksi) | Metric 12.9 (~177ksi) | High-Strength ~170ksi class |
|---|---|---|---|---|
| 3/8″ | 15,904 lbf | 19,880 lbf | 23,415 lbf | 22,531 lbf |
| 7/16″ | 21,648 lbf | 27,059 lbf | 31,870 lbf | 30,667 lbf |
| 1/2″ (calculator default) | 28,274 lbf | 35,343 lbf | 41,626 lbf | 40,055 lbf |
| 5/8″ | 44,179 lbf | 55,223 lbf | 65,041 lbf | 62,586 lbf |
| 3/4″ | 63,617 lbf | 79,522 lbf | 93,659 lbf | 90,124 lbf |
| 1″ | 113,097 lbf | 141,372 lbf | 166,504 lbf | 160,221 lbf |
WORKED EXAMPLE
1/2″ Grade 8 Clevis Bolt Under Rallycross Loading
A rod end mounts to a bracket with a 1/2″ Grade 8 bolt in double shear. The estimated operating shear load is 8,000 lbf under performance-circuit conditions.
- Bolt: 1/2″ diameter, Grade 8 (τ ≈ 90 ksi shear strength).
- Shear area per plane A = π/4×0.5² ≈ 0.196 in². Single-shear capacity ≈ 17,671 lbf. Double-shear capacity ≈ 35,343 lbf.
- Operating load P = 8,000 lbf, Kd = 2.2 (performance circuit / rallycross curb impacts).
- Sf = 35,343 / (8,000 × 2.2) ≈ 2.01 : 1 — clears the SYZ guideline minimum (Sf ≥ 2.0), but only just.
- Given the thin margin, also check bracket/rod-end bearing (tear-out) capacity around the bolt hole — this calculator only checks the bolt itself, not the surrounding material.
Related reading: Ball Joint Linkage Buyer’s Guide →
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