1. What is the Preload Formula?

The preload formula calculates the axial force (preload) generated from applied torque in bolted joints and fastening systems. It is essential for ensuring proper clamping force and joint integrity in mechanical assemblies.

2. How Does the Calculator Work?

The calculator uses the preload formula:

Where:

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

Explanation: The formula accounts for the relationship between applied torque and the resulting axial preload force, considering the torque coefficient and fastener diameter.

3. Importance of Preload Calculation

Details: Accurate preload calculation is crucial for proper bolt tensioning, preventing joint failure, avoiding over-torquing, and ensuring structural integrity in mechanical assemblies.

4. Using the Calculator

Tips: Enter torque in Nm, coefficient (typically 0.2 for dry steel, 0.15 for lubricated), and diameter in meters. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for torque coefficient K?
A: K typically ranges from 0.1 to 0.3, with 0.2 being a common value for dry steel fasteners.

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 does lubrication affect the torque coefficient?
A: Lubrication reduces friction, lowering the K value and resulting in higher preload for the same applied torque.

Q4: What factors influence the torque coefficient?
A: Surface finish, lubrication, thread pitch, material properties, and thread engagement all affect the K value.

Q5: When should measured preload be used instead of calculated?
A: For critical applications, direct measurement using strain gauges or ultrasonic methods provides more accurate preload determination.