Stud Bolts
Manufacturer
India · Mumbai
Anatomy of a Stud Bolt — Two Threaded Ends, No Head
A stud bolt is exactly what the name describes: a straight rod, threaded at both ends (or along its full length), with no head of any kind anywhere on the part. It passes completely through the two flange faces being joined, with a heavy hex nut threaded onto each end and torqued down to draw the flanges together — the clamping load runs from nut to nut through the stud’s tension, exactly as it would through a conventional bolt’s shank, but with no head bearing on either flange face.
This headless design is the reason stud bolts, rather than conventional through-bolts, are the standard fastener for pressure vessel and piping flange connections: because there is no head, both ends of the stud are functionally identical, and the stud itself never needs to be gripped or rotated at all during installation or removal — every turning action happens at the nuts. For high-value, precision-machined flange faces and gaskets, this matters enormously: rotating a stud in place risks scoring the gasket seating surface or disturbing the gasket itself, a risk that simply doesn’t exist when only the nuts turn.
Stud bolts are manufactured in two primary thread configurations — continuous thread along the full body length, and tap-end configuration with a shorter thread length matched to a tapped (threaded) blind hole in one flange, a plain unthreaded waisted section in the middle, and a longer thread on the opposite end for the nut. Both configurations are covered in detail below.
Why Stud Bolts — The Correct Choice for High-Value Flanged Joints
No Head Bearing on Either Flange Face
Because clamping force is applied entirely by the two nuts rather than a head bearing on one flange, both flange faces receive identical, symmetric bearing conditions — important for maintaining even gasket compression across a critical seal.
Even, Controlled Clamp-Up Sequence
Torquing two nuts independently, typically in a cross or star pattern across the full bolt circle, gives far more even and controllable gasket compression across a large flange than a single-sided bolt-and-nut arrangement could achieve.
Simpler Length Adaptation for Thick Flange Stacks
A plain threaded rod is straightforward to manufacture to any length required for a given flange thickness and gasket stack, without needing to also machine a head at a specific, non-adjustable position along the part.
Standard Across Every Major Piping Code
ASME B16.5 and B16.47 flange standards are built around stud bolt fastening as the default method, meaning stud bolts are the specification every downstream engineer, fabricator, and inspector expects for standard flanged connections.
Rotation-Free Installation — Why This Protects the Gasket
On a conventional through-bolt, tightening requires either holding the head stationary while the nut is turned, or turning the head itself while the nut is held — either way, the bolt’s head is in direct, potentially rotating contact with one of the flange faces throughout the tightening process. On a precision-machined flange face carrying a gasket, any rotation at that contact point carries a real risk of scoring the sealing surface or disturbing the gasket’s position before the joint is fully torqued.
A stud bolt removes this risk entirely. Because there is no head, nothing on the stud itself is ever in rotating contact with either flange face — the stud simply passes through both flanges as a straight, stationary member, while all rotational tightening action happens exclusively at the two nuts, safely away from the gasket-bearing surfaces. This is precisely why stud bolts, rather than through-bolts, are specified almost universally on pressure vessel, heat exchanger, and piping flange connections where gasket integrity is directly tied to the safety and reliability of the sealed joint.
The same rotation-free principle also simplifies disassembly during maintenance — technicians can remove nuts from either end without ever needing tooling access to grip or counter-hold the stud itself, useful in confined piping runs where accessing a bolt head from one specific side may not be practical.
Continuous Thread vs Tap-End Stud Bolts
The right configuration depends on whether both ends pass through clearance holes, or one end threads into a tapped hole in the equipment body itself.
Continuous Thread Stud Bolt
Threaded along the complete body length, with a nut free to be positioned or removed at any point. The standard configuration for flange-to-flange connections where both sides use through-clearance holes and a nut at each end.
Tap-End Stud Bolt
A shorter thread length at one end, matched to a tapped (threaded) blind hole machined directly into a valve body, pump casing, or vessel wall — with a plain, unthreaded waisted center section and a longer thread at the opposite end for the nut.
Stud Bolt Material & Strength Options
Grade selection follows service temperature and pressure class — always confirm the correct grade against the matched flange and nut specification.
Stud Bolt Configurations & Related Hardware
Continuous and tap-end stud bolts across the full material range, matched with heavy hex nuts. M6–M100.
Continuous Thread Stud Bolt
Full-length thread per ASTM A193 / ASME B16.5. M6–M100. The default configuration for standard flange-to-flange piping and equipment connections.
Tap-End Stud Bolt
Shorter thread one end, waisted center, longer thread opposite end. M8–M64. For valve bonnet and pump casing connections into a tapped equipment body.
Matching Heavy Hex Nuts
Heavy hex nuts matched to stud bolt thread size and grade, sized for the full torque and bearing area a flange connection requires. View Heavy Hex Nuts →
Custom Stud Bolts
Non-standard lengths, custom thread configurations, and drawing-specific stud bolt sets. Contact sales@akbarfasteners.in with flange size, rating, and grade requirement.
Stud Bolt Size Chart — Common Flange Ratings
Typical stud diameter and quantity per flange size and pressure class — always confirm exact length against actual flange thickness and gasket type.
| Flange Size (NB) | Class 150 | Class 300 | Typical Stud Ø |
|---|---|---|---|
| 2″ | 4 studs | 8 studs | M16 / M20 |
| 4″ | 8 studs | 8 studs | M16 / M20 |
| 6″ | 8 studs | 12 studs | M20 / M22 |
| 8″ | 8 studs | 12 studs | M22 / M24 |
| 10″ | 12 studs | 16 studs | M24 / M27 |
| 12″ | 12 studs | 16 studs | M24 / M30 |
Stud count, diameter, and length vary by exact flange standard and pressure class — always confirm against the specific ASME B16.5 / B16.47 flange drawing before ordering.
Stud Bolts Application Areas
Pressure-retaining flange connections wherever gasket integrity and controlled clamp-up sequencing matter.
Oil & Gas Piping Flanges
process piping joints
Pressure Vessels
manway and nozzle connections
Heat Exchangers
bonnet connections
Valve Bonnet Connections
valve body-to-bonnet joints
Compressor & Pump Casings
tap-end casing connections
Power Generation
boiler and steam piping joints
Marine & Offshore
corrosive service piping
Chemical Processing
exotic alloy stud requirements
Stud Bolt Standards Coverage
Same ISO 9001:2015 quality system as our complete fastener range. Length, thread configuration, and grade verified against ASTM A193/A320 on every production lot.
Complete Documentation Package
Grade / Heat Number
Tensile · Impact · Hardness
Length · Thread Config
Conformance
On Request
Related Bolt Types & Materials
Stud bolts for flange connections. Heavy hex nuts as the standard matched pairing. Hastelloy B-3 for extreme chemical duty. SS 316L for general corrosive service.
Hastelloy B-3 Stud Bolts
The extreme chemical-duty exotic-alloy variant of the standard stud bolt this page describes — for hydrochloric acid and other severely corrosive process environments.
View Hastelloy B-3 Stud Bolts →Heavy Hex Nuts
The standard matched nut for every stud bolt connection — larger across-flats and thicker body sized for flange bearing area and torque requirements.
View Heavy Hex Nuts →SS 316L Fasteners
For stud bolt applications in general corrosive, marine, or chemical process environments where carbon and alloy steel are insufficient.
View SS 316L →Full Bolt Range
Complete bolt manufacturing capability at Akbar Fasteners — stud bolts, hex bolts, socket head, countersunk, and all specialty forms across every material grade.
View Bolt Range →Need Stud
Bolts?
Flange size · rating · thread config (continuous/tap-end) · grade · quantity. Akbar Fasteners Pvt. Ltd. responds within 24 hours.
Export: +91 8696 32 4646 · Support: +91 800 9315 333 · export@akbarfasteners.in