Stud bolts are common in construction, mechanical systems, and industrial piping. They play a key role in clamping heavy components, valued for strength, a simple form factor, and quick assembly. A stud has no head; it’s threaded at both ends and typically works with two nuts to create a secure joint. Because of this configuration, stud bolts are preferred where pressure, heat, or vibration is high such as oil and gas facilities, power plants, shipyards, and heavy machinery lines. Choosing the right option starts with the basics of stud bolts types. These types are applied according to the purpose, and the decision is made based on such factors as the size of the threads, their total length, material grade, and conditions of service. The commonly used types of stud bolts and their applications are listed below; so you can be able to match the application to the fastener.
Different Stud Bolt Types
Let’s discuss in detail the different types of stud bolts and their features.
Fully Threaded (Continuous) Stud Bolts
Fully threaded studs, sometimes called all‑thread or continuous‑thread stud bolts, have threads along their entire length. They are often paired with two nuts to clamp flanges or other components. Two variants are recognised in American Unified inch standards:
- Type 1 continuous stud: this is a general‑purpose stud bolt used for flange bolting. It is measured from end to end and uses UNRC‑2A threads.
- Type 2 continuous stud: this design is intended for high‑temperature and high‑pressure piping. Instead of measuring the overall length, Type 2 studs are measured from the first thread to the first thread (excluding the chamfered points). They are manufactured to ANSI B16.5 dimensions and typically use UNRC‑2A threads for diameters up to 1 inch and 8UNR‑2A threads for larger diameters.
Tap‑End Stud Bolts
Tap‑end studs have a short thread on one end designed to screw into a tapped hole, and a longer thread on the other end for attaching a nut. The tap end typically uses a Class NC5 or Class UNRC‑3A fit to ensure a tight interference with the tapped hole, while the nut end employs a Class UNRC‑2A fit for easy nut installation. The length of a tap‑end stud is measured overall, and the chamfered point on the tap end simplifies engagement with the female thread.
Tap‑end studs are ideal for securing equipment to machinery or for applications where one side of the joint must be flush with a component. They also appear in flange connections when a tapped hole exists on one flange and the other side requires a nut to clamp the joint. Because only one end needs a nut, tap‑end studs may reduce installation time compared with fully threaded rods.
Variants of Tap‑End Studs
Manufacturers offer several sub‑types of tap‑end studs with different body tolerances and finishes. According to American Fastener, tap‑end studs can be:
- Unfinished (Type 1): full‑diameter bodies without standard body tolerances.
- Finished with rolled or cut threads (Type 2): bodies may be undersized or full‑size depending on manufacturing choice; the body is finished to a maximum Class 2A pitch diameter.
- Finished full‑body (Type 3): tolerances equal to the major diameter of Class 2A threads.
- Finished close‑body (Type 4): milled or ground to customer‑specified tolerances.
Double‑End Stud Bolts
Double‑end studs have equal‑length threads at both ends separated by an unthreaded shank. They accommodate a nut on each end and are usually supplied with a Class 2A thread fit. The length is measured overall, and both ends are chamfered to facilitate nut engagement; however, manufacturers may supply studs with round points if requested.
The purpose of the double-end stud bolts is primarily on the connections of the flanges or where there is a requirement to apply torque on both ends. They are perfect in connecting pipes, assembling parts of heavy machinery, or in fixing structures in the areas where the two are both available. Their construction is such that the stress is evenly distributed and chances of bending or fatigue are minimized in contrast to completely threaded rods.
Manufacturing Types of Stud Bolts
As with tap‑end studs, double‑end studs can be supplied in different manufacturing types. The same four categories such as unfinished, finished with rolled or cut threads, finished full‑body and finished close‑body apply to double‑end studs. In addition, metric standards like DIN 938, DIN 939 and DIN 835 specify how the metal end length (the tapped end) is calculated as a multiple of the nominal diameter. These standards help ensure proper engagement in tapped holes and provide guidelines for nut‑end length depending on the overall stud length.
- Hex Studs: A hex stud is a variant of the double‑end stud that includes a hexagon or collar in the middle of the shank. The hex section allows a wrench to grip and tighten the stud during installation without needing to rotate the attached components. Hex studs are threaded at both ends with a collar in the centre. These studs are helpful in equipment maintenance because the hex collar provides an easy torque point without using the nuts, which can reduce the risk of damaging threads.
- Flange Studs: Flange Studs, continuous-threaded chamfer-ended, are used to fasten the pipe flanges. The rounded ends enable nuts to form easily and avoid destruction of gasket surfaces. The body is completely threaded and chamfered at each end with nuts loosely fitted on each side of the flange. Due to a wide range of flange diameter and pressure class, the choice of size and grade is very important; standards like ASME B16.5 give some data on the size and the number of bolts needed by the different flange types.
- Wheel Studs: Wheel studs are special studs used in automotive applications to secure wheels to hubs. They typically feature a threaded end, an unthreaded body with a knurled section, and a head. The knurled section is pressed into the wheel hub to prevent rotation during tightening. Wheel studs are designed to withstand shear and tensile forces generated during vehicle operation. Although not used in flange or piping work, they are included here to illustrate the diversity of stud bolt designs.
Applications of Stud Bolts Across Industries
Stud bolts come with the nature of being strong and easy to fit. That’s why many industries use these stud bolts. Most of the industries that use these bolts are given below.
- Oil and Gas Industry: The oil and gas industry uses these bolts to connect different pipes, flanges, valves, and pressure vessels.
- Power Plants: Power plants need high-heat and pressure-suitable bolts. So most of them use this bolt to make boilers, turbines, and heat exchangers.
- Petrochemical: Plants’ chemical exposure is common here. Stud bolts must resist corrosion while also offering a strong hold.
- Shipbuilding and Marine: Stud bolts are made with features of resistance to saltwater and rust. Which makes them a perfect choice to build ships and marine components.
- Construction: In structural work, stud bolts hold steel frames and joints. They are easy to replace or tighten.
- Automotive and Engines: The automotive industry uses these bolts in different parts of cars and engines because of its high strength and stability with other components.
- Heavy Equipment and Machinery: Stud bolts secure large parts that are hard to move. Their design makes it easier to fix worn-out parts without disturbing the whole setup.
- Aerospace Industry: These bolts are made to handle high pressure and vibration, that is why the aerospace industry uses titanium or alloy steel studs to connect two different components.
How to Choose the Right Stud Bolt
When selecting a stud bolt, you should consider the following factors:
- Type of Application: Determine whether it is going to be in high pressure, high temperature, or high vibration.
- Material Match: You want to make sure the material that you are using can withstand the corrosion, heat and oxidation in your environment.
- Size and Thread: Make sure the bolt is of the correct size fitting and also of the correct type of thread and nut.
- Load Requirements: Ensure that the required load and stress on the bolt do not cause it to bend and break.
- Industry Standards: Quality and reliability: Bolts of the industry are always selected according to the ASTM, DIN, or ISO standards.
Jade Alloys – Trusted Stud Bolt Supplier
Flange joints, machinery and structures are firmly attached by stud bolts. Choosing among fully threaded, tap-end, double-end, hex, flange, or wheel, you have the opportunity to select the correct strength and correct thread fit and length that fits your project. Jade Alloys offers stud bolts that are compliant with ASME B16.5 and ASTM A193 to ensure good installation.It is advisable to always select suppliers that supply ASTM A193/A194-based products, which can give full traceability of MTCs, and give ASL (thread class) and thread length information. Check lead times, stock availability, ask for torque and gasket guidance to have a trouble-free installation. Contact us today!
