What is the difference between hexagon head bolts and hexagonal socket bolts?

Hexagon head bolts and hexagonal socket bolts are two common fasteners in the mechanical field. They have significant differences in structural characteristics, applicable scenarios and operation methods. The head of a hexagon head bolt is in the shape of a regular hexagonal prism with six flat surfaces on the outside. When used, it needs to be clamped and applied from the outside by tools such as open-end wrenches, adjustable wrenches or sockets. Its structure is simple and easy to manufacture.

Because the external hexagonal design makes the force-bearing surface located on the outside of the bolt head, the contact area between the tool and the bolt is large when tightening or disassembling with high torque, so it can withstand large torque and is often used in mechanical manufacturing, construction engineering and other scenes with high strength requirements. However, external hexagon head bolts require sufficient operating space. If there are obstacles around the installation location, the tool may not be inserted normally.

The head of the hexagonal socket bolt is designed to be cylindrical, with a regular hexagonal groove machined inside. A special hexagonal socket wrench (also known as an Allen wrench) must be used to insert it into the hole for rotation. The biggest advantage of this structure is that it saves space. The bolt head is low in height and has smooth edges, which is particularly suitable for the inside of equipment, precision instruments, or occasions where the bolt head needs to be hidden. For example, in furniture assembly or electronic equipment, hexagon socket bolts can not only ensure the connection strength, but also avoid exposed edges and corners that affect the appearance or safety. However, in actual use, if the hexagon socket groove encounters rust or excessive wear, it may cause the wrench to slip and be difficult to disassemble, and the tool adaptation accuracy requirements are higher than those of the external hexagon.

From the perspective of economy and maintenance, the external hexagon head bolt is more suitable for large-scale industrial applications because of its strong tool versatility and low cost; the internal hexagon bolt has more advantages in the field of high-end manufacturing and precision assembly due to its structural characteristics. Although the two bolts have similar functions, the difference in design concepts determines the applicable boundaries of each in engineering practice.