Design Calculators - Mechanical

This calculator determines the required tightening torque for a bolt to achieve a desired preload. It utilizes the common torque-preload relationship involving a K-factor (nut factor) and the bolt's nominal diameter and desired preload force.

Key Inputs:

• Unit System: Select Metric or Imperial units for inputs and outputs.
• Bolt Type/Material: Choose a standard bolt grade to auto-populate typical Proof and Yield Strengths, and an initial K-factor.
• Nominal Diameter: Select a standard bolt size to auto-populate the approximate Stress Area.
• Target Preload Basis: Define how the target preload force is calculated (e.g., percentage of proof/yield strength, or a direct force input).
• K-Factor (Nut Factor): An empirical coefficient that accounts for friction in the threads and under the nut. This value is highly sensitive to lubrication and surface finish and **must be verified** for critical applications.

Calculated Outputs:

• Bolt Proof Strength (\(S_p\)): The maximum stress a bolt can withstand without permanent deformation (used if selected as preload basis).
• Bolt Yield Strength (\(S_y\)): The stress at which a bolt begins to plastically deform (used if selected as preload basis).
• Bolt Stress Area (\(A_s\)): The effective cross-sectional area of the bolt's threads.
• Target Preload Force (\(F_p\)): The desired axial clamping force in the bolt.
• Required Torque (\(T\)): The calculated torque to achieve the target preload.