1. What is Bolt Torque Calculation?

Bolt torque calculation determines the rotational force required to achieve a specific preload (clamping force) in a bolted joint. Proper torque ensures joint integrity without damaging the fastener or components.

2. How Does the Calculator Work?

The calculator uses the bolt torque formula:

Where:

• \( T \) — Torque (Nm)
• \( K \) — Torque coefficient (dimensionless)
• \( F \) — Preload force (N)
• \( D \) — Nominal diameter (m)

Explanation: The torque coefficient accounts for friction and thread geometry, typically ranging from 0.15 to 0.25 for standard fasteners.

3. Importance of Proper Bolt Torque

Details: Correct bolt torque is critical for joint safety, preventing loosening from vibration, avoiding thread stripping, and ensuring proper sealing in pressurized applications.

4. Using the Calculator

Tips: Enter the torque coefficient (typically 0.2 for standard applications), desired preload force in newtons, and nominal bolt diameter in meters. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical torque coefficient value?
A: For standard unlubricated steel fasteners, K is typically 0.2. Lubricated fasteners may have values as low as 0.15.

Q2: How do I determine the required preload force?
A: Preload is typically 60-75% of the bolt's proof load, which depends on bolt material, grade, and size.

Q3: Why does diameter affect torque?
A: Larger diameters create more leverage, requiring less force to achieve the same torque, but more torque to achieve the same preload.

Q4: Are there limitations to this formula?
A: This simplified formula assumes consistent friction and doesn't account for thread pitch, which may be significant in precision applications.

Q5: Should I use a torque wrench for critical applications?
A: For critical joints, consider using calibrated torque wrenches, torque-angle methods, or direct tension indicators for more accurate preload control.