What Is Interference Fit in Engineering? h7/p6 Designation Explained

24 April 2026

Verified by Rachel Mayfield, Supply Chain Analyst - April 2026

A high-quality image of numerous white plastic screw caps piled together, showcasing industry production.
Photo by Birgit Böllinger on Pexels
Interference Fit is an assembly where the shaft is larger than the hole, requiring force or heating to assemble. Example: h7/p6. In practical applications, Interference Fits are used in a variety of engineering contexts such as gears, couplings, bearings, and bushings. This type of fit ensures components stay tightly connected under dynamic loads, enhancing mechanical stability and performance. The British Institute for Machine Tools Design (BTMA) recommends interference fits for high-precision assemblies where a secure connection is important. Interference Fits comply with international standards such as ISO 286-1:2010 and BS EN ISO 4756:2010, which specify tolerances and fit designations. These standards help in selecting the right components for specific applications. For example, a h7/p6 designation indicates a shaft with an outer diameter slightly larger than the hole's inner diameter, ensuring the parts press fit securely. Common values range from 0 to +0.15 mm for standard interference fits, depending on the application and material used. For instance, when assembling a bearing onto a shaft made of EN8 carbon steel, an interference fit ensures that the component remains in place during operation. Similarly, stainless steel components like A2-70 can use Interference Fits to maintain structural integrity under high stress. When selecting engineering components for Interference Fit assemblies, it's important to consider material properties and compatibility. For example, mating surfaces made of different materials may require specific lubricants or coatings to prevent galling and ensure a smooth assembly process. The British Lubricating Engineers Association (BLEA) provides guidelines on suitable lubricants for interference fits. In summary, Interference Fits are important in engineering applications requiring strong connections. Adhering to established standards and carefully selecting material grades ensures optimal performance and longevity of the assembled components.

Where this data comes from: Supplier listings are verified against Companies House public records. Product specifications reference published ISO, BS, and DIN standards. Trade body data is sourced from official member directories.

Frequently Asked Questions

What is Interference Fit?

An assembly where the shaft is larger than the hole, requiring force or heating to assemble. Example: H7/p6.

What is an Interference Fit?

An Interference Fit is a type of assembly where the shaft diameter is larger than the hole's inner diameter, requiring force or heating to fit them together. This method ensures components remain tightly connected under dynamic loads, enhancing mechanical stability and performance.

How do you select the appropriate interference fit for an application?

The selection process involves considering factors like the load requirements and materials used in the assembly. For example, a h7/p6 designation is commonly used to indicate that the shaft has an outer diameter slightly larger than the hole's inner diameter, providing a secure press fit.

Which standards are relevant for Interference Fits?

International standards such as ISO 286-1:2010 and BS EN ISO 4756:2010 provide guidelines on tolerances and fit designations for Interference Fits. These standards help engineers choose the right components based on specific application needs.

Where can UK engineers find suppliers for parts using Interference Fit?

UK engineers can consult with suppliers listed under trade bodies like BTMA, which recommends manufacturers who supply high-precision assemblies that use Interference Fit to ensure secure connections in critical applications.

What are the cost implications and availability of components requiring Interference Fit?

The cost and availability of parts using Interference Fit depend on the specific application and material used. For instance, standard interference fits range from 0 to +0.15 mm, with higher precision leading to increased costs but better performance in demanding environments.

What is Interference Fit and why is it important in engineering?

Interference Fit is a type of assembly where the shaft diameter exceeds the hole's inner diameter, necessitating force or heating to fit them together securely. This method ensures components remain tightly connected under dynamic loads, enhancing mechanical stability and performance.

How do engineers determine the appropriate interference fit for their application?

Engineers choose the right interference fit by considering factors like load requirements, materials used (such as EN8 carbon steel), and specific applications such as gears or bearings. Standards like ISO 286-1:2010 provide guidelines on tolerances and designations to help select suitable components.

What are some common standards that dictate the specifications for Interference Fits?

Common standards for Interference Fits include BS EN ISO 4756:2010, which specifies how to achieve proper fits through designated tolerances. These guidelines ensure compatibility and performance across different engineering applications.

Where can UK engineers find suppliers offering components suitable for Interference Fit assemblies?

UK engineers can visit the British Institute for Machine Tools Design (BTMA) website or other reputable trade bodies listed on mlc.org.uk to find suppliers providing parts that comply with ISO standards. These suppliers offer a range of materials and sizes suitable for various applications requiring secure connections.