1. What is a Preload Torque Calculator for Steel?

Definition: This calculator determines the torque required to achieve a specific preload force in steel bolts.

Purpose: It helps engineers and technicians properly tighten bolts to achieve optimal clamping force without over-torquing.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( T \) — Torque (Newton-meters)
• \( k \) — Friction factor (dimensionless, steel-specific)
• \( F \) — Pretension force (Newtons)
• \( d \) — Bolt diameter (meters)

Explanation: The torque is calculated by multiplying the friction factor, pretension force, and bolt diameter.

3. Importance of Preload Torque Calculation

Details: Proper torque calculation ensures bolt integrity, prevents loosening, and maintains joint strength in steel structures.

4. Using the Calculator

Tips: Enter the friction factor (default 0.2 for steel), pretension force in Newtons, and bolt diameter in meters. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical friction factor for steel?
A: For steel-on-steel, k is typically 0.2, but can range from 0.15 to 0.3 depending on surface conditions.

Q2: How do I determine pretension force?
A: Pretension is typically 70-90% of bolt proof load, which can be calculated from bolt grade and diameter.

Q3: Why does diameter affect torque?
A: Larger diameters create greater leverage, requiring more torque to achieve the same clamping force.

Q4: Should I lubricate bolts?
A: Lubrication reduces friction (lower k value), meaning less torque is needed for the same preload.

Q5: How accurate is this calculation?
A: This provides an estimate. For critical applications, consider testing with torque wrenches and load cells.