What is the difference between shoulder diameter and thread diameter?

In a shoulder bolt, the shoulder diameter is always larger than the thread diameter. For example, an 8mm shoulder bolt typically has an M6 thread.

How do I measure a shoulder bolt?

Shoulder bolts are identified by their shoulder diameter and shoulder length. The thread length is usually a standard fixed dimension based on the shoulder size.

What does "ISO 7379" signify?

This is the international standard that specifies the dimensions, tolerances, and material requirements for metric socket head shoulder bolts.

Can I use a shoulder bolt as a standard screw?

No. Their primary purpose is to provide a precision bearing surface. Using them as a standard screw may result in improper seating because the shoulder will stop against the workpiece.

Why are they called stripper bolts?

They earned this name from their frequent use in stripper plates within tool and die sets, where they guide the plate that strips the material off a punch.

Are the shoulders hardened?

Yes, alloy steel shoulder bolts are typically through-hardened to Property Class 12.9, providing a wear-resistant surface for rotating parts.

What tolerance are the shoulders ground to?

Most metric shoulder bolts conform to an f9 or h8 tolerance, ensuring a sliding fit with standard bearings and bushings.

Do I need a specific tool to install these?

You simply need a standard metric hex key (Allen wrench) that matches the socket size in the head.

Can these be used in high-vibration environments?

Yes, the high-strength alloy steel and secure hex drive make them excellent for machinery, though thread-locking fluid is often used for extra security.

Is stainless steel as strong as alloy steel for shoulder bolts?

No. While stainless steel (A2) offers better corrosion resistance, alloy steel (Grade 12.9) has much higher tensile and yield strength.

Shoulder Bolt, Socket Head

Precision-ground for exacting tolerances, our ISO 7379 socket head shoulder bolts provide a smooth, unthreaded bearing surface for rotation or sliding applications. Built for durability and accuracy, these versatile fasteners are essential for pulleys, linkages, and pivot points in mechanical assemblies.

Disclaimer: Product images are representative. Product specifications and descriptions govern the item you will receive.

Socket Head Shoulder Bolts — Metric Sizes

What Are Socket Head Shoulder Bolts?

Socket head shoulder bolts, also known as stripper bolts, are specialized fasteners characterized by an unthreaded cylindrical shoulder between the head and the threaded portion. This shoulder is precision-ground to a specific diameter and length, allowing it to act as a pivot point, bearing surface, or guide rail for moving parts. The socket head allows for high-torque tightening using a standard hex key, making them ideal for applications with limited space or high mechanical requirements.

Manufactured to ISO 7379 standards, these bolts are designed to provide both a secure fastening point and a precision axle in a single component. They are widely used in die-and-mold work, automotive assemblies, and automated machinery.

Key Features and Benefits

Precision-Ground Shoulders: Shoulders are ground to tight tolerances (typically f9 or h8) to ensure smooth rotation and minimal play in pivot applications.
High-Torque Socket Drive: The internal hex drive prevents slipping and allows for higher clamping force on the threaded end compared to slotted alternatives.
Versatile 3-in-1 Design: Acts as a bolt, a shaft, and a spacer, reducing the number of components needed in an assembly.
Durable Material Grades: Available in high-strength alloy steel (Grade 12.9) and corrosion-resistant stainless steel.

Materials and Finishes

Alloy Steel (Grade 12.9): Heat-treated for maximum tensile strength and durability. Typically finished with black oxide for mild corrosion resistance.
Stainless Steel (A2 / 304): Ideal for applications exposed to moisture or chemicals where rust prevention is critical.

Common Applications

Pivot Points: Acting as axles for pulleys, gears, and linkages.
Stripper Springs: Used in die sets to guide and limit the travel of stripper plates.
Guides: Serving as slide rails or stops in jigs and fixtures.
Bearing Mounts: Providing a precision surface for mounting small ball bearings.

Frequently Asked Questions (FAQs)

What is the difference between shoulder diameter and thread diameter? In a shoulder bolt, the shoulder diameter is always larger than the thread diameter. For example, an 8mm shoulder bolt typically has an M6 thread.
How do I measure a shoulder bolt? Shoulder bolts are identified by their shoulder diameter and shoulder length. The thread length is usually a standard fixed dimension based on the shoulder size.
What does "ISO 7379" signify? This is the international standard that specifies the dimensions, tolerances, and material requirements for metric socket head shoulder bolts.
Can I use a shoulder bolt as a standard screw? No. Their primary purpose is to provide a precision bearing surface. Using them as a standard screw may result in improper seating because the shoulder will stop against the workpiece.
Why are they called stripper bolts? They earned this name from their frequent use in "stripper plates" within tool and die sets, where they guide the plate that strips the material off a punch.
Are the shoulders hardened? Yes, alloy steel shoulder bolts are typically through-hardened to Property Class 12.9, providing a wear-resistant surface for rotating parts.
What tolerance are the shoulders ground to? Most metric shoulder bolts conform to an f9 or h8 tolerance, ensuring a "sliding fit" with standard bearings and bushings.
Do I need a specific tool to install these? You simply need a standard metric hex key (Allen wrench) that matches the socket size in the head.
Can these be used in high-vibration environments? Yes, the high-strength alloy steel and secure hex drive make them excellent for machinery, though thread-locking fluid is often used for extra security.
Is stainless steel as strong as alloy steel for shoulder bolts? No. While stainless steel (A2) offers better corrosion resistance, alloy steel (Grade 12.9) has much higher tensile and yield strength.