Screw Torque Calculator

Screw Torque Formula Explanation

The screw torque calculation utilizes the following formula:

\[ Ts = K \cdot F \cdot d \cdot (1 - \frac{L}{100}) \]

where:

• \(Ts\) is the Screw Torque in pound-feet (lb-ft),
• \(K\) is the material constant,
• \(d\) is the nominal bolt diameter in feet (ft),
• \(F\) is the axial bolt force in pounds-force (lbf),
• \(L\) is the force lost due to lubrication, expressed as a percentage (%).

Example Calculation

For an example, let's assume you have a normal steel bolt with the following properties:

• Material Constant (K): 0.2 (for normal steel bolts)
• Nominal Bolt Diameter (d): 0.05 ft (0.6 inches)
• Axial Bolt Force (F): 1000 lbf
• Lubrication Loss (L): 10%

Substituting these values into the formula, we get:

\[ Ts = 0.2 \cdot 1000 \cdot 0.05 \cdot (1 - \frac{10}{100}) = 9 \text{ lb-ft} \]

This calculation demonstrates how to determine the screw torque necessary for a specific application, taking into account factors such as material constant, bolt diameter, axial force, and lubrication loss.

Common FAQs

1. What is the significance of the material constant in the formula?

   • The material constant (K) accounts for the properties of the bolt material, affecting how the torque translates into clamping force.

2. How does lubrication affect screw torque?

   • Lubrication decreases the friction between the bolt threads and the nut, reducing the torque needed to achieve a specific clamping force. However, it also means that the effective torque applied can be less than without lubrication, as represented by the \(L\) value in the formula.

3. Can this formula be used for all types of screws and bolts?

   • While the formula provides a general approach to calculating screw torque, specific conditions and materials may require adjustments or considerations beyond this basic formula, especially for specialized or high-strength fasteners.

This calculator and guide simplify the process of determining screw torque for various applications, ensuring the appropriate force is applied for secure and reliable fastening.