Terminology in Threaded Fastener

Basic Threaded Fastener Terminoloy 

1. Chamfered End 

A chamfer point is a tapered or beveled end on the screw that allows for easier insertion into a material. It helps the screw to initiate contact and begin threading into the material more smoothly.

2. Thread Length

It is the length of the threaded portion of the screw, measured from the underside of the head to the end of the threads.

3. Thread 

A screw thread is characterized by the helical shape that running around the exterior of a shank. When engaged by a screwdriver or wrench, thread transforms rotational motion into linear movement, facilitating the insertion of the screw into the material.

4. Run Out

It is the position where the threaded section transitions into the bolt shank.

5. Grip Length

The grip length of a screw refers to the portion of the screw that is unthreaded, typically measured from the underside of the head to the beginning of the threaded section. In other words, it is the length of the shaft that does not have threads. The grip length is important in fastener design and selection as it determines how well the screw or bolt will secure the joint or material.

6. Body Shank

The screw shank refers to the main, cylindrical body of the screw between the head and the threads. It is the section of the screw that does not include the head or the threaded part. The shank is often smooth and unthreaded, providing the structural support for the screw.

7. Fillet Radius

It typically refers to the curved transition area between the screw head and the shank. This is the part of the screw where the head meets the shank, designed to reduce stress concentrations and enhance overall strength.

8. Bearing Surface

The screw bearing surface refers to the part of the screw that makes contact with the surface of the material being fastened. It is the area of the screw that bears the load and provides the clamping force to hold materials together.

9. Across Flat

The dimension "across flat" refers to the distance between two opposite flat surfaces of the hexagon, particularly in the case of nuts and bolt heads, such as those with hexagonal (hex) shapes.

10. Head

A screw head is the top part of a screw that provides a surface for external force to be applied during installation or removal. The design of the screw head varies, and different types of screw heads are used for specific applications.