What is the purpose of a flange on certain types of bolts?

The purpose of a flange on certain types of bolts is to increase the bearing surface and prevent pull-through. This design feature allows the flange to distribute the load over a larger area, which helps to minimize the risk of the bolt being pulled through the material it is fastened to. By providing this increased surface area, the flange effectively reduces the stress concentration at the point of contact, enhancing the bolt's holding capacity. This characteristic is particularly important in applications where high torque or shear forces are present, ensuring that the fastened assembly remains secure under various conditions. Additionally, the flange helps to maintain alignment of the bolt in the installation, further contributing to its effectiveness in preventing pull-through.