Fastener Preload

Mechanical & Motion

Estimated bolt preload from installation torque and nut factor. Estimate only.

App id: MECH-14. Reference version 1.0.

How to fill it

Fill the inputs. The tool shows the outputs.

On the tool screen, Calc is the working sheet. Presets stores values you reuse. Reference is the formula, assumptions, and provenance below.

Formula

F = T / (K d)

Inputs

Name	Unit
Installation torque	`N-m`
Nominal diameter	`mm`
Nut factor K	`1`
Target preload (optional)	`kN`

Outputs

Name	Unit
Estimated preload (hero result)	`kN`
Fraction of target	`%`

Diagnose

Observations are context. They do not pass or fail a structure. See Diagnose.

When	Observation	Severity
`Every result`	Estimate only	caution

Assumptions

K must be supplied for the actual lubrication, coating, and thread condition.
Actual preload can vary substantially from this estimate.

Provenance

Nut-factor approximation T = K F d. Friction dominates. Not a substitute for a specified torque.