The tolerance for gap is determined by what characteristic of the fastener?

The tolerance for gap in a fastener is primarily determined by its diameter. This is because the diameter of a fastener plays a crucial role in how it fits into a predetermined hole or assembly. A proper fit is essential to ensure that the fastener can adequately transfer loads, maintain structural integrity, and prevent issues such as wobbling or loosening over time.

When a fastener's diameter is specified, it inherently dictates the amount of space that exists between the fastener and the hole it fits into, hence controlling the overall gap. Variations in the diameter can directly influence the clearance between connected parts and affect how securely components are held together. Therefore, understanding the significance of diameter allows for the correct assessment of tolerance for gaps in mechanical assemblies, which is vital for maintaining safety and performance in aerospace applications.