20.0mm (M16) x 40mm Shoulder Bolt ISO 7379 A2 Stainless Steel

ISO 7379 Shoulder Bolts

ISO 7379 shoulder bolts are precision-engineered fasteners distinguished by their unthreaded cylindrical shoulder, which has a larger diameter than the threaded portion. This specific design allows them to serve multiple functions beyond simple fastening, acting as a crucial component for precise alignment and movement within mechanical assemblies.

These bolts are a cost-effective solution for a variety of applications where a robust, reliable, and reusable shaft or pivot is required. Common uses include:

• Pivots and Shafts: The smooth, cylindrical shoulder provides a bearing surface for moving parts like pulleys, gears, and levers, allowing them to rotate freely with minimal friction.

• Stationary Guides and Locating Pins: The precision shoulder is perfect for guiding other components or for ensuring parts are correctly positioned relative to each other in jigs and fixtures.

• Linkages: In mechanical linkages and mechanisms, the shoulder bolt can connect moving parts, facilitating smooth and controlled motion.

A critical feature of the ISO 7379 standard is the f9 tolerance applied to the shoulder diameter.

What is an f9 Tolerance?

An f9 tolerance is an internationally recognized standard that defines the acceptable size variation for a component. The designation is broken down into two parts:

• The letter 'f' indicates a clearance fit. This means the bolt's shoulder is specifically manufactured to be slightly smaller than the nominal diameter, ensuring it will easily fit into a corresponding hole of the same nominal size.

• The number '9' refers to the International Tolerance (IT) grade. This grade specifies the width of the tolerance zone, or the total allowable range of deviation. A grade of 9 indicates a relatively wide tolerance compared to a tighter grade like 6 or 7, but it is still precise enough for the guiding and pivoting applications of a shoulder bolt.

In practice, an f9 tolerance ensures that each shoulder bolt's diameter is consistently held within a very specific, predictable range, guaranteeing a repeatable, clearance-based fit every time. For a specific nominal shoulder diameter, the f9 tolerance provides a minimum and maximum allowable diameter.

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• Unique Shoulder Lengths: Manufacturing bolts with a longer or shorter shoulder to fit a particular assembly.

• Special Materials: Using materials other than the standard steel or stainless steel, such as brass, aluminum, or special alloys for specific environmental or load requirements.

• Different Thread Sizes: Combining a standard shoulder diameter with a non-standard thread size.

Custom manufacturing ensures that the bolt's dimensions and properties are perfectly matched to the application's needs, offering a flexible solution for complex designs.

To illustrate, here's a general table of f9 tolerances for common nominal shoulder diameters:

Note: The values in the table are a standard representation. The term "Lower Deviation" refers to the difference between the maximum material limit and the nominal size, while the "Upper Deviation" refers to the difference between the minimum material limit and the nominal size.

Custom Manufacturing

While ISO 7379 provides a wide range of standard sizes, there are many applications where a custom bolt is required. Manufacturers can produce shoulder bolts to customer drawings and specifications. This allows for specific modifications to be made, such as:

• Non-standard Shoulder Diameters: Creating a shoulder with a diameter not covered by the ISO standard.

• Unique Shoulder Lengths: Manufacturing bolts with a longer or shorter shoulder to fit a particular assembly.

• Special Materials: Using materials other than the standard steel or stainless steel, such as brass, aluminum, or special alloys for specific environmental or load requirements.

• Different Thread Sizes: Combining a standard shoulder diameter with a non-standard thread size.

Custom manufacturing ensures that the bolt's dimensions and properties are perfectly matched to the application's needs, offering a flexible solution for complex designs.