What Are the Types of Bolts?
Buyers often list “bolts” in RFQs without knowing the exact type they need.
There are many bolt types—each designed for different loads, assemblies, and environments.
In my work with global B2B buyers, I’ve seen costly delays caused by wrong bolt selections. Let’s simplify the categories and definitions so you choose the right bolt every time.
How Many Types of Bolts Are There?
It’s easy to assume bolts are all the same—but that leads to sourcing errors.
There are more than 12 standard types of bolts used in manufacturing and construction.
Each bolt type has a unique head shape, thread length, and purpose. Here are 10 of the most commonly used bolts:
- Hex Bolt
- Carriage Bolt
- Flange Bolt
- Eye Bolt
- U-Bolt
- J-Bolt
- Anchor Bolt
- Shoulder Bolt
- T-Bolt
- Lag Bolt
- Elevator Bolt
- Stud Bolt
Bolt Type Overview Table
| Bolt Type | Head Style | Best Use |
|---|---|---|
| Hex Bolt | Hex head | Machinery, metal-to-metal joints |
| Carriage Bolt | Round head | Wood assemblies |
| Eye Bolt | Loop head | Lifting, securing cables |
| Flange Bolt | Integrated washer | Engines, automotive systems |
| Anchor Bolt | Threaded end | Fixing to concrete |
At Prime, we manufacture and stock all of these types, including custom-coated and metric sizes. We also offer engraved head bolts upon request.
What Is a Bolt Without a Head Called?
Buyers often refer to these as “threaded rods,” but there’s a more precise term.
A bolt without a head is usually called a “stud bolt.” It has threads on both ends and no driving head.
Stud bolts are often used in flanged piping, engines, and high-pressure machinery. One end threads into the base, the other connects with a nut.
Stud Bolt Key Features
| Feature | Description |
|---|---|
| No head | Allows double-nut connection |
| Threaded ends | Full or partial thread |
| Applications | Valves, flanges, pipe assemblies |
We supply ASTM A193 B7 stud bolts with full certifications to clients in the oil & gas sector. Every stud is double-checked for tensile strength, threading, and straightness.
What Is a Hollow Bolt Called?
Hollow bolts are often seen in fluid or fuel systems. But clients sometimes call them “pipe screws” or “vent bolts.”
A hollow bolt is called a “banjo bolt.” It allows fluid to pass through the center.
Banjo bolts are used with banjo fittings in hydraulic and fuel systems. They feature holes through the bolt shaft and side walls.
Banjo Bolt Design
| Feature | Function |
|---|---|
| Hollow shaft | Allows liquid or gas to pass |
| Cross-drilled hole | Connects with fluid channels |
| Threaded end | Tightens with nut or housing |
We supply CNC-machined banjo bolts for automotive and machinery use. Available in stainless, brass, or carbon steel—with optional zinc, phosphate, or nickel plating.
What Do You Call a Bolt With Threads on Both Ends?
This type is critical in high-torque environments and secure clamping systems.
A bolt with threads on both ends is called a “stud” or “stud bolt.”
Stud bolts can be fully threaded or partially threaded. One end is fixed into a tapped hole, while the other uses a nut for tightening.
Threaded Stud Applications
| Application | Why Stud Bolts Are Used |
|---|---|
| Flange assembly | Quick and secure fastening |
| Engine blocks | Withstand heat and vibration |
| Pipe joints | Maintain alignment during pressure |
One of our clients in Europe uses M12 x 120 stud bolts with PTFE coating for chemical-resistant pipe systems. We ensure all batches meet DIN 976 or ANSI B16.5 specs, packed with clear part labels for easy inspection.
Conclusion
Bolts come in many forms—headless, hollow, double-threaded—each with unique functions.
Need help choosing the right bolt?
At Prime, we offer a full catalog of bolts—custom, standard, and specialty.
🔩 Hex, flange, stud, banjo, anchor, and more
📦 ISO-certified quality with full specs and fast lead time
🧰 Custom finishes, coatings, and thread standards
📩 Send us your drawing or spec today for a quick quote and expert bolt selection advice!
