Tooling U-SME Fasteners Practice Test 2025 - Free Fasteners Knowledge Questions and Study Guide

The primary use of a bar key in an assembly is to join parts such as gears or wheels onto a cylindrical shaft in a specific position. This fastening method is essential in mechanical applications to ensure that the components rotate together without slipping, providing a reliable transmission of torque. Bar keys fit into a keyway—an elongated slot on the shaft and in the part being attached—allowing the components to be firmly and accurately aligned for proper function.

Bar keys are designed to maintain a consistent alignment between the mechanical elements, preventing any axial movement which could lead to misalignment and potential failure during operation. This makes them particularly important in various machinery, such as motors and gearboxes, where precise positioning is crucial for efficiency and longevity.

Other options focus on assembly methods that have different applications. For example, securing walls together or supporting heavy loads involves different types of fasteners or structural supports, while attaching electrical components generally requires connectors or screws specifically designed for electrical assembly.