Understanding the Different Types of Fastener Threads
Custom threaded fasteners are critical components in a wide variety of industrial and commercial equipment. They are known for various advantages including strength, ease of installation, cost-effectiveness and removability. They are also available in different sizes for a variety of applications.
Despite all these benefits, shopping for different types of threaded fasteners is not an easy task. The reason is simple, there are too many types of fasteners. You can eliminate many models by considering several aspects such as material, size and thread type. While many customers are familiar with sizes and materials, they may not be aware of the different types of threads. We decided to address this issue by providing this article.
Understand basic thread design
Typically, fastener threads come in two designs—coarse or fine. Each design has its own advantages. Let's take a look at them.
Coarse pitch threads: These threads are designed with a large thread start and higher flank engagement. Coarse threads prevent nicks or any other type of damage. They are easy to install without wear and fitting problems. For these reasons, industrial applications often choose fasteners with coarse threads.
Thin Wire: Thin wire is designed for greater shear and stretch capabilities. This is because the manufactured threads have small diameters and areas of large tensile stress. Fine threads allow for greater fastener adjustment in the application. They can be used for thin wall sections and materials that may be difficult to tap.
Types of Fastener Threads
The following points will help in understanding the different thread types used to manufacture custom threaded fasteners:
Unified National Coarse (UNC): This is the most common thread type used in most fasteners. UNC threads do not require cross-threading during manufacturing and are known for their high tolerance levels. The reason is that they help the fastener install deeper into the application, but also allow for easy removal.
Unified National Fine (UNF): This thread type is widely used in fasteners in industries such as aerospace. They are designed with extremely tight tolerances and tension adjustments. UNF threads are also known for carrying heavy loads. Therefore, they are used in applications that require precise fastener assembly.
United National Extra Fine (UNEF): A thread type designed to be finer than UNF threads, UNEF threads are unique because they are used in specialized applications. These may include thin threaded walls and threaded holes in hard and thin materials.
UNJC and UNJF Threads: These "J" thread types are primarily used in the manufacture of bolts. Threads can be made on the inside or outside of the fastener. For bolts, manufacturers prefer to create external threads because they create small areas of stress, large root radii, and areas of tension.
UNK and UNR threads: Both UNK and UNR are external threads. UNR threads are similar to UNC threads, but with a larger fillet radius. UNK threads are similar to UNR threads, but they have a smaller root radius and diameter.