Bolt Preload Calculator: operating questions
Does target preload determine tightening torque?
Not by itself. Tightening torque also depends strongly on thread and bearing-surface friction, geometry, lubrication and the selected tightening method. This tool deliberately reports load rather than inventing a torque coefficient.
Why use tensile stress area instead of shank area?
A threaded fastener normally develops its governing axial stress through the reduced effective tensile area of the thread. Use the value defined for the actual thread standard and pitch.
Can the target be set to 100% of proof load?
That leaves no allowance for preload scatter, embedding, external load or uncertainty. The acceptable target and tightening scatter must follow the joint design method and controlled assembly process.
| Parameter | Unit | Example |
|---|---|---|
| Tensile stress area | mm² | 84.3 |
| Proof strength | MPa | 600 |
| Target preload | % proof load | 70 |