Torque-Angle & Torque-to-Yield (TTY) Calculator
Calculate bolt stretch elongation, axial clamping preload force, hex nut flat rotation, and fastener reusability from torque-plus-angle specifications.
Calculated Results
Frequently Asked Questions
Why do modern automotive engines use torque-angle tightening instead of torque alone?
Friction in bolt threads and under the bolt head absorbs up to 90% of torque reading variation (dirt, oil, thread roughness). By setting a low baseline snug torque followed by a precise rotational angle (e.g. 90°), the bolt stretches by an exact physical thread pitch distance, ensuring uniform clamping pressure across the cylinder head.
Why MUST Torque-to-Yield (TTY) bolts be discarded after one use?
TTY bolts are engineered to stretch past their elastic limit into the 'plastic deformation' zone to maintain maximum constant clamping force. Once stretched plastically, the steel will not return to its original length; reusing a TTY bolt causes it to snap or lose clamping pressure, blowing head gaskets.
What does 'turn of the nut' mean in structural steel?
In AISC structural building and bridge construction, the turn-of-the-nut method specifies bringing a bolt to a snug-tight condition and then turning the nut an additional 1/3 to 2/3 turn (120° to 240°) to guarantee minimum required tensile preload.
Should you apply engine oil to bolt threads before torquing?
Always follow the vehicle service manual. Engine manufacturers usually specify motor oil or assembly lube on threads and underside of bolt heads. Applying lube to dry torque specs drastically over-tightens the bolt.