KEVOS® MAKEOS · Fasteners
Turn-of-Nut Angle for Bolt Preload
Through what angle must the nut turn to reach this preload, or what preload does a given turn give?
Nut rotation for a target bolt preload by the handbook’s turn-of-nut relation, using the bolt’s elastic elongation over its shank and threaded lengths, with optional joint compliance, or the preload from a specified turn angle.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Solve for | choice | Find the angle for a preload, or the preload for an angle. |
| Target preload | kN | Preload required. |
| Turn angle (preload mode) | ° | Nut turn from the snug position. |
| Thread lead | mm | Thread lead (pitch × starts). |
| Nominal (shank) diameter | mm | Nominal diameter, for the shank area. |
| Tensile stress area | mm² | Tensile stress area of the thread. |
| Unthreaded shank length in the grip | mm | Length of plain shank within the grip. |
| Threaded length in the grip | mm | Length of loaded thread within the grip (often plus about half a nut height for the thread engagement). |
| Bolt elastic modulus | GPa | Elastic modulus of the bolt. |
| Joint stiffness (0 = rigid joint) | kN/mm | Stiffness of the clamped parts; 0 reproduces the handbook relation, which ignores joint compression. |
Method and formulas
- Bolt elongation B = F_t (L_s ÷ A_s + L_t ÷ A_t) ÷ E.
- Handbook: θ = 360 B ÷ l, with l the lead (θ = 360 F_t L_B ÷ E l).
- With joint compliance the nut also takes up the joint compression: θ = 360 (B + F_t ÷ k_j) ÷ l.
- Example: 35 kN in an M10 bolt with a 1.5 mm lead needs 22.716° from snug on a rigid joint.
Limitations
- Elastic region; yield-tightening needs empirical angles.
- Not valid for gaskets or soft joints without measured joint stiffness; establish angles on a simulated joint.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Set an angle-tightening specification for a bolted joint
- Check what preload a turn angle produces
- Compare angle and torque tightening
Who it is for
- Design engineers
- Assembly engineers
- Maintenance fitters
What you get
- Bolt elongation
- Turn angle or preload
- Bolt stiffness
Interpreting the result
- Find the snug point consistently; most of the scatter in angle tightening comes from where counting starts.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1522–1528. Topic reference; no source tables or recommended settings are reproduced.
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