Bolt & Stud Types

Classifying Bolts

• Used with and without nuts, bolts are recognizable by the presence of a threaded shaft and a head. Bolts come in a variety of sizes, thread types and head shapes, as well as tolerance levels to pressure. The standard thread type has closely spaced threads called a fine thread, while wood and machine threads have a looser design known as coarse thread. Sizes for both types vary depending on need. Head types include hexagonal, rounded, socket cap and flat. In addition, some styles of bolts do not have a head, while others have a smooth U or J shape, or a circular ring in place of the head.

Classifying Studs

• Unlike bolts, studs do not have a head. Instead, traditional studs consist of an almost fully threaded shaft with an unthreaded space in the middle known as a shank. Each end has a different thread tolerance, with one providing additional thread interference. Certain models have threads that run continuously from end to end without a shank in the middle.

Types of Bolts

• Of the 10 different types of bolts, each has a distinct appearance, with some designed for specific applications. Hex bolts are distinguished by a fine thread, hexagonal head and flat tip. Lag bolts also have hexagonal heads but have a coarse thread known as wood thread and a pointed tip. Carriage bolts resemble hex bolts but instead of a hexagonal head, they sport a smooth rounded head. In place of a head, eye bolts have a ring, often used in the securing of chains or ropes, as well as a fine thread and flat tip. U and J bolts have the same design but with a U or J shape in place of the head. Shoulder bolts are specifically designed for the creation of pivot points and have a socket cap, fine threads and flat tip. Configured for use in the construction of conveyor systems, elevator bolts have a smooth, flat head; fine thread at only one end; and a flat tip. Sex bolts are used in connection with mating screws; unlike other bolt models, which have a thread on the exterior of the shaft, they have threading on the interior of a hollow shaft. These bolts are often in situations that require a head situated on each side of the joint. Hanger bolts also differ from the standard bolt design in that they lack a head and have both fine and coarse threading. One end has a flat tip, while the other has a pointed tip.

Stud Types

• Studs come in three main designs: continuous thread, tap end and double end. Continuous thread studs do not have a middle shank but instead, as implied by the name, have a continuous fine threading throughout. With flat ends, this type of stud requires two nuts during assembly. Tap-end studs use only one nut, which is applied to threading on the one end. The other end, separated from the first by a shank, has threads that allow the stud to be screwed into a tapped hole. Like continuous thread studs, double-end studs use two nuts fixed to each end. Each side is threaded, and they are separated by a shank. Both sides have fine threads and flat ends.