1. What is the Fastener Torque Equation?

The fastener torque equation calculates the torque required to achieve a specific preload in a bolted joint. It's fundamental in mechanical engineering for ensuring proper fastener tension and joint integrity.

2. How Does the Calculator Work?

The calculator uses the torque equation:

Where:

• \( T \) — Torque (Nm)
• \( F \) — Preload force (N)
• \( d \) — Nominal diameter of fastener (m)
• \( K \) — Torque coefficient (unitless)

Explanation: The equation accounts for the relationship between applied torque, desired preload, fastener size, and friction conditions.

3. Importance of Torque Calculation

Details: Proper torque calculation ensures bolted joints have sufficient clamping force without over-tightening, which can lead to fastener failure or joint damage.

4. Using the Calculator

Tips: Enter preload in newtons, diameter in meters, and torque coefficient (typically 0.15-0.25 for dry steel). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical torque coefficient (K) value?
A: For dry steel fasteners, K is typically 0.15-0.25. Lubricated fasteners may have K values as low as 0.10.

Q2: Why is preload important in bolted joints?
A: Preload creates clamping force that keeps joints tight under operating conditions and prevents loosening from vibration.

Q3: How accurate is this torque calculation?
A: Actual torque can vary ±25% due to friction variations. For critical applications, direct tension measurement is recommended.

Q4: Should I use metric or imperial units?
A: The calculator uses metric units (N, m). For imperial, convert lb-ft to Nm (1 lb-ft = 1.35582 Nm) and inches to meters.

Q5: What affects the torque coefficient?
A: Surface finish, lubrication, thread pitch, and material combinations all influence the K factor.