When it comes to fastening heavy-duty components in industries like oil & gas, petrochemicals, construction, and mechanical engineering, stud bolts are the go-to choice. They’re designed to handle extreme pressure, temperature, and vibration — making them essential for flanges, pipelines, pressure vessels, and structural assemblies.
But here’s the tricky part: stud bolts come in a wide range of sizes, and choosing the wrong one can lead to serious failures. That’s where a stud bolt size chart becomes crucial. In this guide, we’ll explore everything you need to know about stud bolts — their types, dimensions, standards, and of course, a comprehensive size chart you can rely on.
What is a Stud Bolt?
A stud bolt is a threaded rod with threads on both ends, usually without a head. Nuts are fastened on both ends to create a secure connection between two components. Unlike regular bolts, which are tightened from one side, stud bolts provide strength, balance, and uniform load distribution across the joint.
They are commonly used in flange connections, especially in pipelines that transport oil, gas, steam, or chemicals.
Why Stud Bolt Size Matters
Imagine assembling a pressure vessel that handles thousands of PSI of internal pressure. If your bolts are too short, they won’t fully engage with the nut. If they’re too long, you risk uneven torque or interference with nearby components.
The correct size ensures:
Safety – Prevents leaks and mechanical failures.
Efficiency – Ensures proper tightening and torque.
Standardization – Makes replacement easier across projects.
Cost-effectiveness – Avoids wasted material and rework.
Common Standards for Stud Bolts
Stud bolts are manufactured according to international standards to maintain uniformity. The most commonly followed standards include:
ASME B16.5 – Covers pipe flanges and flange fittings.
ASME B16.47 – Large-diameter flanges.
ASTM Standards (A193, A320, etc.) – Define material grades.
DIN & ISO Standards – European and international equivalents.
Types of Stud Bolts
Before we dive into size charts, let’s quickly look at the different types of stud bolts:
Full Thread Stud Bolts – Threaded along the entire length.
Tap-End Stud Bolts – Threaded differently on each end, used for special applications.
Double-End Stud Bolts – Equal length of thread on both sides with an unthreaded middle section.
For flange connections, full thread stud bolts are the most widely used.
How to Measure a Stud Bolt
When using a stud bolt size chart, you’ll come across terms that define bolt dimensions:
Nominal Diameter (D): The diameter of the stud bolt (e.g., M12, 1/2″).
Length (L): The overall length of the stud bolt, excluding chamfers.
Thread Pitch (P): Distance between threads, usually in mm (metric) or threads per inch (imperial).
Nut Size (Across Flats): The corresponding nut dimension for tightening.
Stud Bolt Size Chart (ASME B16.5 Standard Flanges)
Here’s a reference chart showing commonly used stud bolt sizes for flanges (up to Class 600).
| Nominal Pipe Size (NPS) | Flange Class | Stud Bolt Diameter (inches) | Number of Studs | Stud Bolt Length (mm) |
|---|---|---|---|---|
| 1/2″ | 150 | 1/2″ | 4 | 75 |
| 1″ | 150 | 5/8″ | 4 | 90 |
| 2″ | 150 | 5/8″ | 4 | 100 |
| 3″ | 150 | 5/8″ | 8 | 110 |
| 4″ | 150 | 3/4″ | 8 | 120 |
| 6″ | 150 | 3/4″ | 12 | 130 |
| 8″ | 150 | 7/8″ | 12 | 140 |
| 10″ | 150 | 1″ | 16 | 150 |
| 12″ | 150 | 1″ | 16 | 160 |
| 16″ | 150 | 1-1/8″ | 20 | 170 |
| 20″ | 150 | 1-1/4″ | 24 | 180 |
| 24″ | 150 | 1-1/4″ | 24 | 190 |
⚙️ Note: Sizes vary with flange pressure class (150, 300, 600, 900, etc.). Always verify with ASME or project specifications before procurement.
Metric Stud Bolt Size Chart
For projects following ISO / DIN standards, here’s a metric reference:
| Stud Bolt Size | Pitch (mm) | Across Flats (Nut) | Typical Length Range (mm) |
|---|---|---|---|
| M8 | 1.25 | 13 | 30 – 100 |
| M10 | 1.50 | 17 | 40 – 150 |
| M12 | 1.75 | 19 | 50 – 200 |
| M16 | 2.00 | 24 | 60 – 250 |
| M20 | 2.50 | 30 | 80 – 300 |
| M24 | 3.00 | 36 | 100 – 400 |
| M30 | 3.50 | 46 | 120 – 500 |
| M36 | 4.00 | 55 | 150 – 600 |
Materials Used for Stud Bolts
Stud bolts are manufactured from various materials depending on the application:
Carbon Steel (ASTM A193 B7) – Most common, high strength.
Alloy Steel – Used in high-temperature services.
Stainless Steel (ASTM A193 B8/B8M) – Corrosion-resistant, ideal for chemical plants.
Duplex & Super Duplex – Excellent resistance to seawater and aggressive environments.
Inconel, Monel, Hastelloy – Specialized alloys for extreme conditions.
Applications of Stud Bolts
Stud bolts are indispensable in heavy industries. Some common applications include:
Pipeline Flanges – Oil, gas, and water pipelines.
Pressure Vessels – Boilers, reactors, and storage tanks.
Petrochemical Plants – High-pressure and corrosive services.
Marine Industry – Shipbuilding and offshore platforms.
Structural Engineering – Heavy steel connections.
Tips for Selecting the Right Stud Bolt
When choosing a stud bolt, keep these points in mind:
Check flange standard (ASME, DIN, ISO).
Match diameter and length with the flange bolt circle.
Select appropriate material grade based on service conditions.
Consider corrosion and temperature resistance.
Always cross-check with project specifications.
Advantages of Using Stud Bolts
Provide even stress distribution compared to headed bolts.
Allow easier maintenance since nuts can be removed without disturbing alignment.
Suitable for high-pressure, high-temperature environments.
Widely available in standardized sizes.
Understanding Flange Connections with a Stud Bolt Size Chart
Flanges are one of the most common applications where stud bolts are used. A stud bolt size chart helps engineers quickly determine which bolt dimensions match the bolt circle diameter (BCD) and thickness of the flange. For example, ASME B16.5 specifies the number of bolts, bolt diameter, and length required for each flange size and pressure class.
Without a proper chart, there’s a high chance of selecting an incorrect bolt length, which can lead to uneven tightening. This could result in leaks when the system is pressurized, especially in oil & gas pipelines. By using the chart as a reference, maintenance teams save time, ensure standardization, and reduce costly mistakes.
Benefits of Keeping a Stud Bolt Size Chart Handy
For professionals working in fabrication shops, refineries, or construction sites, having a stud bolt size chart easily accessible brings multiple benefits:
Quick Selection: Instead of guessing or manually measuring, engineers can cross-check directly from the chart.
Standard Compliance: Ensures that only ASME, DIN, or ISO-approved sizes are used.
Inventory Management: Stores and suppliers can stock the right sizes without over-ordering.
Training Tool: New engineers and technicians learn faster when they can visually see the relationship between pipe size, flange rating, and bolt dimensions.
Whether in print, PDF, or mobile format, these charts act as a universal reference across industries.
Conclusion
A stud bolt size chart is more than just a reference table — it’s a vital tool that ensures safety, precision, and reliability in mechanical assemblies. Whether you’re working on a small pipe connection or a massive pressure vessel, using the correct stud bolt size can make all the difference between a secure joint and a dangerous failure.
Always verify dimensions, material grades, and standards before procurement. Keep this guide handy as a reference, and you’ll save time, money, and potential headaches in your next project.
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