A stud bolt (or double-end stud) is a threaded rod without a head, threaded on both ends. One end screws into a tapped hole (or has two nuts), and the other end receives a nut for clamping. They are common in flange joints and high-temperature applications.

How is stud bolt torque calculated?

The same formula as standard bolts: T = K × d × F, where K is the nut factor, d is the nominal diameter, and F is the target preload. The preload is F = η × Rp × As.

Why use stud bolts instead of regular bolts?

Stud bolts are preferred when: (1) the joint must be assembled/disassembled frequently, (2) high-temperature service (avoids bolt head distortion), (3) tapped holes in cast iron or aluminum, (4) flange connections per ASME B16.5.

What is the nut factor K for stud bolts?

The nut factor is the same as for standard bolts: K ≈ 0.20 for dry steel, 0.15 for lubricated, 0.12 for anti-seize paste. For stud bolts, both nut-bearing surfaces must be considered if two nuts are tightened.

Should I torque both nuts on a stud bolt?

In most flange applications, only the nut on the free end is torqued. The end screwed into the tapped hole (or the bottom nut on a through-stud) is installed to a snug fit first. In double-nut configurations, both nuts are torqued in a cross-pattern sequence.

Free Engineering Tool

Stud Bolt Torque Calculator

Calculate tightening torque and preload for double-end stud bolts. Same torque approach as standard bolts, adapted for stud applications.

ISO 898-1VDI 2230ASME PCC-1

Stud Size

Property Class

Utilization η (%)

Nut Factor K

Quick presets

Results

Target Torque

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Preload Force

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Yield Load (100%)

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Stress Area

—

Utilization

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Stud Bolt Preload & Torque

Same equations as standard bolts. For stud bolts, ensure consistent lubrication on nut threads and bearing surface for predictable preload.

⚠️ Torque-based tightening has ±25% uncertainty. For critical flange joints, hydraulic tensioning is preferred.

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