1. What is Preload Calculation?

Preload calculation determines the axial force (F) applied to a bolted joint based on torque (T), coefficient (K), and diameter (D). It's essential for ensuring proper bolt tension 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)
• \( D \) — Bolt diameter (m)

Explanation: This formula calculates the axial force generated in a bolt when a specific torque is applied, accounting for friction and geometric factors through the coefficient K.

3. Importance of Preload Calculation

Details: Accurate preload calculation is crucial for maintaining joint integrity, preventing bolt failure, ensuring proper sealing, and avoiding loosening under vibration in mechanical assemblies.

4. Using the Calculator

Tips: Enter torque in Nm, 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 K value for bolts?
A: For standard steel bolts, K typically ranges from 0.15 to 0.25, with 0.2 being a common default value.

Q2: Why is preload important in bolted joints?
A: Proper preload ensures the joint remains tight under operating conditions, prevents leakage, and maintains structural integrity.

Q3: How does lubrication affect the K coefficient?
A: Lubrication reduces friction, which decreases the K value and increases the preload for the same applied torque.

Q4: What units should be used for diameter?
A: Diameter should be entered in meters for consistent SI unit calculations (1 mm = 0.001 m).

Q5: Can this formula be used for all bolt types?
A: While the basic formula applies to most bolts, specific applications may require adjustments for thread type, material, and surface conditions.