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Torque to Preload Formula:
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The torque to preload formula calculates the axial force (preload) generated in a bolted joint from the applied torque, using the formula F = T / (K × D), where F is the preload, T is the torque, K is the nut factor (coefficient), and D is the nominal diameter.
The calculator uses the torque to preload formula:
Where:
Explanation: This formula converts applied torque to the resulting axial clamping force in a bolted joint, accounting for friction and geometric factors through the nut factor K.
Details: Accurate preload calculation is essential for proper bolted joint design, ensuring sufficient clamping force while preventing bolt failure from over-tightening. It affects joint integrity, vibration resistance, and fatigue life.
Tips: Enter torque in Nm, nut factor (typically 0.15-0.35 for standard conditions), and nominal diameter in meters. All values must be positive and non-zero.
Q1: What is the typical range for nut factor K?
A: For standard conditions, K typically ranges from 0.15 to 0.35, but can vary based on surface finish, lubrication, and thread type.
Q2: Why is preload important in bolted joints?
A: Proper preload ensures joint integrity, prevents loosening under vibration, and maintains sealing pressure in gasketed joints.
Q3: How accurate is this calculation?
A: Accuracy depends on the precision of the nut factor value. Actual preload can vary ±25% or more due to friction variations.
Q4: When should direct measurement be used instead?
A: For critical applications, direct measurement methods (ultrasonic, strain gauges) should be used for more accurate preload determination.
Q5: Does this formula work for all bolt types?
A: The formula is generally applicable but may require adjusted K values for special thread forms or materials.