bolts
When does an application warrant the use of a bolt instead of a screw? Screws and bolts are the most commonly used mechanical fasteners. Although similar and sometimes referred to interchangeably, screws and bolts offer unique features and are ideal for different applications. A screw is an externally threaded fastener, typically used to assemble objects with threads. A bolt, on the other hand, is used to assemble unthreaded objects and usually with the use of a nut. Unlike some screws, bolts are not self-tapping and are only partially threaded. A self-tapping
fastener is one that can tap its own hole as it is driven into the material. Screws (if self-tapping) are designed to be installed in a pre-drilled or pilot hole, or (if self-drilling) can tap their own hole during installation — thanks to a sharp, drill-bit point and full threading. Most significantly, screws do not use a nut to retain the assembly. For this reason, they’re shorter than the width of the fastened part and do not protrude through to the other side. It’s the friction at the threads, which is the force that keeps the parts securely fastened.
The most common type of bolt is the hex bolt. It has a hexagonally shaped head, providing a flat surface for tools to apply torque during fastening.
14
December 2021 www.fastenerengineering.com
DESIGN WORLD
