EngineerBenchScreening bolt size for an applied load
Bolt size depends on how the joint transfers load, not just the total force. This screening calculation divides the entered load across the bolt count and compares the resulting tension and shear with the model's material strength basis. Equal sharing is an assumption, not a property of every bolt pattern.
Identify the loaded section
Select the bolt property class and check whether threads cross the shear plane. The threaded section has less effective area than the full shank. Enter the design factor deliberately; increasing it does not account for a missing load case or an incorrect joint model.
What a size result leaves unresolved
A screened diameter does not establish resistance to fatigue, slip, prying, thread stripping, or failure of the joined plates. Preloaded and eccentric joints need additional checks. Use the result to narrow a candidate size, then verify the complete joint against the requirements of its application.
Turning a joint load into a screening load
For a concentric load shared equally by four identical bolts, the model assigns one quarter of the entered force to each bolt. That assumption becomes questionable when the load is eccentric, the joint is flexible, or clearances cause one bolt to engage before the others. A larger bolt count can reduce the calculated share without resolving those physical effects.
Separate tensile and shear components according to the actual load path. A force parallel to the joint interface does not necessarily enter a preloaded bolt as direct shear while friction is maintained. Likewise, a bracket can introduce bending and prying that a simple axial-force entry misses. The selected property class supplies the model's strength basis; it does not certify an unknown fastener's material. Use the output as a candidate for further checks on plate thickness, edge distance, thread engagement, washers, and installation. If the application is governed by a specific code, use that code's complete connection method and load combinations rather than adopting the screening diameter as an approved size.
Formula
Quadratic interaction: utilization = √((factored tension / proof capacity)² + (factored shear / shear capacity)²).