1. What is Bolt Preload Calculation?

Bolt preload calculation determines the tensile force applied to a bolt when tightened with a specific torque. This force is crucial for maintaining joint integrity and preventing loosening under operational loads.

2. How Does the Calculator Work?

The calculator uses the bolt preload formula:

Where:

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

Explanation: The formula calculates the axial force generated in a bolt when a specific torque is applied, considering the bolt diameter and friction coefficient.

3. Importance of Preload Calculation

Details: Proper preload ensures bolt joints remain tight under vibration and load variations, prevents fatigue failure, and maintains sealing pressure in gasketed joints.

4. Using the Calculator

Tips: Enter torque in Nm, torque coefficient (typically 0.15-0.25 for standard bolts), and 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 is typically between 0.15-0.25, but varies with lubrication, surface finish, and thread condition.

Q2: Why is preload important in bolted joints?
A: Proper preload prevents joint separation, reduces fatigue loading, and maintains clamping force under operational conditions.

Q3: How accurate is this calculation?
A: Accuracy depends on precise K values. For critical applications, experimental determination of K is recommended.

Q4: Does this work for all bolt types?
A: The formula applies generally, but specific bolt designs may require modified calculations or testing.

Q5: What affects the torque coefficient?
A: Surface finish, lubrication, thread pitch, material combination, and washers all influence the torque coefficient value.