Calculator Form
Example Data Table
| Case | Load | Bolts | Shear Planes | Diameter | Efficiency | Shear Stress |
|---|---|---|---|---|---|---|
| Single Bolt, Single Shear | 8,000 N | 1 | 1 | 12 mm | 100% | 70.7 MPa |
| Two Bolts, Double Shear | 18,000 N | 2 | 2 | 12 mm | 95% | 41.9 MPa |
| Four Bolts, Single Shear | 45,000 N | 4 | 1 | 16 mm | 90% | 62.2 MPa |
| Four Bolts, Double Shear | 45,000 N | 4 | 2 | 16 mm | 90% | 31.1 MPa |
These example values help users compare single shear, double shear, bolt count, and load distribution effects before entering project data.
Formula Used
The calculator treats stress in N/mm² internally, which equals MPa. If you select psi or ksi, the page converts values for input display and output display.
Use nominal shank area for unthreaded shear planes. Use root diameter area when threads cross the shear plane. Use custom area when a standard, specification, or manufacturer gives a net resisting area directly.
Load share efficiency models imperfect force sharing across multiple fasteners. Lower efficiency reduces total effective resisting area and raises computed shear stress.
How to Use This Calculator
- Enter the applied load and choose the matching load unit.
- Enter the number of bolts and the number of shear planes.
- Choose the area basis: shank, root diameter, or custom area.
- Set load share efficiency to reflect how evenly the bolts share force.
- Enter material strength data and select manual or derived allowable stress mode.
- Click the calculate button to show results above the form.
- Review actual stress, allowable stress, utilization, factor of safety, and graph.
- Download the result summary as CSV or PDF when needed.
Frequently Asked Questions
1) What is bolt shear stress?
Bolt shear stress is the average internal stress created when a transverse force tries to slide connected parts across the bolt’s cross section. It equals applied shear force divided by the effective resisting area.
2) What is the difference between single and double shear?
Single shear has one shear plane through the bolt. Double shear has two planes, so the same load is shared across twice the resisting area, which lowers average shear stress.
3) Should I use shank area or thread root area?
Use shank area when the smooth shank crosses the shear plane. Use root area when threads lie in the shear plane. Root area is smaller and therefore more conservative.
4) Why is load share efficiency important?
Multiple bolts rarely share force perfectly because of hole tolerance, stiffness differences, and fit-up errors. Efficiency reduces the ideal total area so the stress estimate better reflects uneven loading.
5) What does factor of safety mean here?
It compares allowable shear stress to actual computed shear stress. A value above 1.0 means the current stress is below the chosen allowable limit. Larger values indicate more reserve capacity.
6) Can I enter an allowable stress directly?
Yes. Select manual allowable stress mode and enter the value in the selected stress unit. This is useful when you already have code-based allowable limits or manufacturer design data.
7) Does this replace a full structural design check?
No. It is a focused shear stress tool. A full connection design may also require bearing, tear-out, tension, block shear, prying action, slip resistance, fatigue, and code-specific resistance checks.
8) Why does the graph look linear?
With constant bolt area and constant efficiency, shear stress is directly proportional to applied load. Doubling the load doubles the stress, so the load-stress relationship plots as a straight line.