Zinc Plated White Carbon Steel Shoulder Metal Bolts Phillips Slotted Blue Bolts In 1/2 1/8 1

A shoulder bolt, also referred to as a shoulder screw or stripper bolt, is a specialized fastener designed for applications requiring precision, alignment, and controlled movement. Its unique design distinguishes it from standard bolts, making it a critical component in machinery, automation, and mechanical systems.

A shoulder bolt is characterized by its three-part structure:

• Head: Typically designed for tool engagement, such as a hex head or socket head, to allow for easy installation and removal.
• Shoulder (Unthreaded Section): A smooth, cylindrical shank with a precise diameter, larger than the threaded portion. This section acts as a bearing surface or spacer.
• Threaded End: A smaller-diameter threaded section that secures the bolt into a tapped hole or nut.

The shoulder's length and diameter can be customized to meet specific mechanical requirements, making it adaptable to a wide range of applications.

The shoulder bolt's unthreaded shank ensures accurate alignment of components, such as gears, pulleys, or levers, by maintaining a consistent axis of rotation. It also acts as a spacer, controlling the distance between parts to prevent interference or misalignment. This is particularly important in assemblies like automotive transmissions or industrial machinery.

The smooth shoulder provides a low-friction surface for rotating or pivoting parts, such as hinges, linkages, or bearings. Unlike fully threaded bolts, the shoulder eliminates contact between threads and moving components, reducing wear and ensuring smooth operation. This function is essential in robotics, conveyor systems, and other dynamic applications.

The shoulder's larger diameter distributes shear and axial loads over a broader area, reducing stress concentrations and preventing deformation of softer materials like plastic or aluminum. This enhances the durability of the assembly, particularly in high-load environments such as injection molding or heavy machinery.

By isolating the threaded section from moving parts, the shoulder prevents damage to the threads during assembly, disassembly, or operation. This extends the bolt's lifespan and reduces maintenance requirements in equipment like printing presses or CNC machines.

In plastic injection molding, shoulder bolts are commonly used in ejector systems. The shoulder guides the ejector plate during the demolding process, ensuring smooth, linear motion while the threaded end secures the assembly. The shank's strength withstands lateral forces, protecting the threads from wear and tear.

Shoulder bolts are typically made from high-strength materials such as alloy steel, stainless steel (for corrosion resistance), or thermoplastics (for lightweight applications). They can be heat-treated or coated (e.g., zinc plating) to enhance durability and performance. While standard sizes are available, custom dimensions (shoulder length, diameter, and thread size) can be manufactured to meet specific design requirements.

304 is a general-purpose stainless steel that is widely used to make equipment and machine parts that require good all-round performance (corrosion resistance and formability). To maintain the corrosion resistance inherent in stainless steel, the steel must contain more than 18% chromium, more than 8% nickel content. 304 stainless steel is a grade of stainless steel produced according to the American ASTM standard.

A2 is a class of 304 stainless steel, A4 is a class of 316 stainless steel. The fastener industry sometimes refers to 302HQ and 304 as A2, while 316 and 316L (carbon content C less than 0.3%) are referred to as A4.