Torque & Preload

Calculate the recommended tightening torque and resulting clamp load based on thread size, material grade, and lubrication condition.

Custom Overrides (Optional)
Overrides standard selections if filled out.
%
Standard is 75% of Proof Load.
Assembly Specifications
Target Torque

--

ft-lbs
(-- in-lbs)
Clamp Force (Preload)

--

lbs
Bolt Proof Load 0 lbs
Tensile Stress Area 0.000 in²
Torque & Preload Physics

When you tighten a bolt, it stretches like a stiff spring. This stretching creates the "Preload" (clamping force) that holds the joint together. The goal of torque is simply to generate this stretching force.

The Torque Formula
$T = K \cdot D \cdot F_p$
T = Torque, K = Friction Factor, D = Nominal Dia, Fp = Preload Force
The Danger of Lubrication

Notice how drastically torque requirements drop when applying Anti-Seize ($K=0.10$) versus dry steel ($K=0.20$). If you use the dry torque spec on a lubricated bolt, you will generate 2x the clamping force and likely snap the fastener.

Proof Strength

Proof strength is slightly lower than yield strength. It is the maximum tension the bolt can withstand without permanent (plastic) deformation. Standard engineering practice aims for 75% of Proof Load for reusable joints.