Hexagonal nuts are used in conjunction with screws and bolts to connect and fasten machine parts. The most widely used type is the 1 type six nuts, with C nuts suitable for applications where surface roughness and precision requirements are not critical. A and B nuts are used for more polished surfaces and higher precision requirements.

Type 2 hexagonal nuts have greater thickness (M) and are often used in applications requiring frequent assembly and disassembly. Thin hexagonal nuts have reduced thickness and are used where space is limited on connected machine parts.

Hexagonal nuts are classified by nominal thickness into Type I, Type II, and thin varieties. Nuts above grade 8 are divided into Type 1 and Type II. The design of hexagonal nuts provides excellent torque transmission capacity and can withstand significant axial and radial loads.

Hexagon nuts come in various classifications and specifications to meet different engineering needs. Category 1 hexagon nuts feature single-sided chamfers, while category 3 has double-sided chamfers. Pocket nuts with non-through screw holes are used decoratively, particularly in playground equipment where exposed bolt ends might be hazardous. Butterfly nuts are ideal for space-constrained applications like automobile wheels.