Which type of fit allows for very tight component assembly?

An interference fit is designed for very tight component assembly, where one part is intentionally made larger than the other part it's meant to fit onto. This type of fit is used when a strong connection is needed because the components are pressed together, resulting in a secure assembly that resists movement or separation under load.

Interference fits are commonly used in applications such as gears and pulleys, where components need to be firmly locked in place to ensure consistent operation and minimize play. They require a certain level of force to assemble the parts and often rely on additional techniques like heating one part or chilling the other to ease the assembly process.

This type of fit contrasts with other options like slight clearance fits, which provide space between components to allow for relative movement, and transition fits, which combine aspects of both interference and clearance but do not offer the same level of tightness. A loose fit, as the name implies, would not provide the required tightness for a secure assembly.