Half Threaded Rod Stud Bolts are a type of fastener characterized by threading on only one portion (typically half or less) of their overall length, with the remaining section being a plain, unthreaded shank. This design offers a unique combination of strong threaded engagement where needed, along with a smooth, unthreaded portion that can serve various functions, such as acting as a guide, providing shear strength, or allowing for rotational movement without thread wear.

Definition

A Half Threaded Rod Stud Bolt is a headless fastener that features external threading on one end or section of its length, while the rest of the rod remains unthreaded and smooth. The threaded portion is designed for engagement with a nut or an internally threaded hole, providing a secure fastening point. The unthreaded shank—often referred to as the grip length or smooth shank—can pass through materials without causing damage, provide a precise fit in clearance holes, or serve as a pivot or spacer, depending on the application. This design optimizes the use of threading only where necessary, preventing unnecessary thread exposure or interference.

Advantages

• Optimized Shear Strength: The unthreaded, larger diameter shank provides superior shear strength compared to a fully threaded rod, as the full cross-sectional area of the bolt resists shear forces.
• Reduced Thread Damage: The smooth shank prevents threads from being damaged during insertion through clearance holes, especially in multi-plate assemblies.
• Improved Seating and Alignment: The plain shank can act as a guide, ensuring components align correctly during assembly and providing a better bearing surface.
• Prevents Thread Corrosion/Wear in Critical Areas: In applications where the unthreaded portion passes through corrosive environments or areas of high wear, the absence of threads can prolong fastener life.
• Flexibility in Grip Length: Allows for specific grip lengths to be maintained for optimal clamping force, especially in bolted connections where controlled stretch is desired.

Applications

• Structural Steel Connections: Often used in heavy-duty structural applications where high shear strength is critical, such as connecting beams, columns, and other load-bearing components.
• Flange Connections (especially high-pressure): In large diameter or high-pressure flanges, the unthreaded portion ensures that the bolt shank fits precisely through the flange holes, reducing stress concentrations.
• Engine and Machinery Assembly: Employed in engine mounts, large pump assemblies, and industrial machinery where precise alignment and high shear resistance are required.
• Bridge Construction: Used in various bridge components to connect heavy structural elements, providing strength and durability against dynamic loads.
• Renewable Energy Systems: Found in wind turbine assemblies and other large-scale renewable energy infrastructure where robust and precisely engineered fasteners are essential.