Bolt torque/tension calc



The Bolt Torque/Tension calculation provides a simple estimation of the tension in a bolt based on the torque imposed or vice versa. The calculation is based on a formula derived from AS4100, which is a standard for steel structures. The formula is often used to estimate the tension in 'snug tight' bolts.

The formula used in the Bolt Torque/Tension calculation is:

T = (K * T) / D

where: T is the tension in the bolt (in pounds or newtons), K is the nut factor (dimensionless), T is the torque applied to the bolt (in foot-pounds or Newton-meters), and D is the bolt diameter (in inches or millimeters).

The nut factor, K, represents the relationship between torque and tension for a specific bolt and nut combination. It takes into account factors such as friction, thread pitch, and thread conditions. The nut factor is typically determined through testing or provided by bolt manufacturers.

The Bolt Torque/Tension calculation provides an estimate of the tension in a bolt for a given torque value or vice versa. It is important to note that this calculation provides an approximation and relies on assumptions about the specific bolt and nut combination. Factors such as surface conditions, lubrication, and thread engagement can influence the actual tension achieved for a given torque.

The term 'snug tight' refers to the recommended level of bolt tightness where the bolt is tightened securely but not excessively. It is a preloading condition commonly used in steel structures to ensure sufficient clamping force while allowing for potential adjustments or future tightening if necessary.

When using the Bolt Torque/Tension calculation, it is important to consider the specific application requirements, design standards, and safety factors. Consulting applicable design codes and standards, as well as seeking guidance from qualified engineers, is advisable to ensure proper bolted connection design and installation.

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29 Apr 2009
Last Modified
19 Jul 2023
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Comments: 2
JohnDoyle[Admin] 12 years ago
I'm not aware of any calculation hosted here Nick. I can see that it would be a useful addition or extension to existing bolt calculations like this one.[Admin]
Nick1729 12 years ago
Do you have a Bolt Torque/Tensioning calculation sheet for heat exchanger/pressure vessel flanges? Best Regards,Nick Nazari