1. What is the Bolt Torque To Preload Formula?

The bolt torque to preload formula calculates the torque required to achieve a specific preload force in a bolted joint. This is essential for ensuring proper clamping force and joint integrity in mechanical assemblies.

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 formula accounts for the relationship between applied torque, desired preload force, bolt size, and friction characteristics.

3. Importance of Bolt Torque Calculation

Details: Accurate torque calculation is crucial for ensuring proper joint clamping, preventing bolt failure, avoiding loosening under vibration, and maintaining structural integrity.

4. Using the Calculator

Tips: Enter torque coefficient (typically 0.15-0.25 for standard bolts), preload force in Newtons, and nominal diameter in meters. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical torque coefficient value?
A: For standard steel bolts, K typically ranges from 0.15 to 0.25, but varies with lubrication, surface finish, and thread condition.

Q2: How do I determine the required preload force?
A: Preload force depends on joint requirements, typically 60-75% of bolt proof strength for critical applications.

Q3: Why is accurate torque important?
A: Under-torque can lead to joint loosening, while over-torque can cause bolt stretching or failure.

Q4: Does this formula account for thread pitch?
A: No, this simplified formula assumes the torque coefficient K accounts for all friction and geometric factors.

Q5: When should I use a more complex formula?
A: For precision applications or when detailed friction data is available, more comprehensive formulas considering thread pitch may be used.