Press Fit Engineering and Design Calculator

Tolerances, Engineering Design & Limits & Fits

An interference fit, also known as a press fit or friction fit, is a fastening between two parts which is achieved by friction after the parts are pushed together, rather than by any other means of fastening.

For metal parts in particular, the friction that holds the parts together is often greatly increased by compression of one part against the other, which relies on the tensile and compressive strengths of the materials the parts are made from. Typical examples of interference fits are the press fitting of shafts into bearings or bearings into their housings and the attachment of watertight connectors to cables. An interference fit also results when pipe fittings are assembled and tightened.

Industry standard interference fits have been established by ASME/ANSI B4.1-1967 revised 2009. It is recommended that for typical end engineering design applications this standard be used.

• Locational interference fits, LN are used where accuracy of location is of prime importance, and for parts requiring rigidity and alignment with no special requirements for bore pressure. Such fits are not intended for parts designed to transmit frictional loads from one part to another by virtue of the tightness of fit. These conditions are covered by force fits.
• Force or shrink fits FN) constitute a special type of interference fit, normally characterized by maintenance of constant bore pressures throughout the range of sizes. The interference, therefore, varies almost directly with diameter, and the difference between its minimum and maximum value is small to maintain the resulting pressures within reasonable limits.

Use this engineering calculator to determine engineering and design parameters for cylindrical press fit applications.

Press Fit Engineering and Design Equations (See Below)

• Alexander Slocum, MIT Department of Mechanical Engineering (Analaysis, Formula and Reference Calcs)
• Calculator Contribution: Santhosh Mallala, Hyderabad, TG India

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