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Preload Torque Calculator

Formula

The formula to calculate the preload torque is:

$Tpl = \left(\frac{yp}{100} \cdot S \cdot A\right) \cdot \frac{d}{12}$

Where:

$Tpl$ is the Preload Torque (lbf-ft)
$yp$ is the preload percentage (%)
$S$ is the tensile yield (psi)
$A$ is the area (in²)
$d$ is the nominal diameter (in)

What is Preload Torque?

Preload torque refers to the torque required to apply a specific preload (tension) to a fastener, such as a bolt. This preload ensures that the fastener is properly tensioned to hold components together securely. The preload torque is calculated based on the preload percentage, tensile yield, cross-sectional area, and nominal diameter of the fastener.

Example Calculation 1

Let's assume the following values:

Preload Percentage (yp) = 75%
Tensile Yield (S) = 50000 psi
Area (A) = 0.5 in²
Nominal Diameter (d) = 1 in

Using the formula:

$Tpl = \left(\frac{75}{100} \cdot 50000 \cdot 0.5\right) \cdot \frac{1}{12} = \left(0.75 \cdot 50000 \cdot 0.5\right) \cdot \frac{1}{12} = 1562.5 \text{ lbf-ft}$

The Preload Torque is 1562.5 lbf-ft.

Example Calculation 2

Let's assume the following values:

Preload Percentage (yp) = 60%
Tensile Yield (S) = 60000 psi
Area (A) = 0.75 in²
Nominal Diameter (d) = 1.5 in

Using the formula:

$Tpl = \left(\frac{60}{100} \cdot 60000 \cdot 0.75\right) \cdot \frac{1.5}{12} = \left(0.6 \cdot 60000 \cdot 0.75\right) \cdot \frac{1.5}{12} = 27000 \cdot \frac{1.5}{12} = 3375 \text{ lbf-ft}$

The Preload Torque is 3375 lbf-ft.