Nut-factor relationship
Torque to preload
Inputs
Applied tightening torque for the one stated fastener.
Nominal bolt shank diameter used in the nut-factor relationship.
User-entered nut factor; friction and lubrication strongly affect it.
User-entered one-sided uncertainty magnitude from 0 to 100.
Results
A wrong number here has physical consequences. Check the method and the boundary below before using this result, and have it reviewed by someone accountable for the design.
Nominal preload
33.333
Estimated lower preload
25
Estimated upper preload
41.667
P = T / (K·D); uncertainty band = P(1 ± u)
A first-pass number, not a code check, certification, or approval. Read the method and its limits below. What this is and is not.
Nearby: Axial response · Beam deflection & reactions · Elastic stability · Solid-shaft torsion
Method
Formula, when it applies, and when it does not
Estimate a nominal preload from applied torque, nominal diameter, and a torque coefficient with uncertainty made explicit.
P = T / (K·D); uncertainty band = P(1 ± u)
When
- One preloaded fastener
- Nominal diameter approximation
Don’t
- Torque is an indirect and friction-sensitive way to create preload. This screen does not determine allowable preload, bolt proof/yield, thread strength, joint stiffness, separation, fatigue, thermal effects, relaxation, lubrication procedure, or a safe tightening specification.
NASA RP-1228, Fastener Design Manual