US bolts are commonly used in industrial applications, such as power generating equipment, Navy ships, pumps, valves and more. The majority of these bolts are made of stainless steel and some have a Zinc coating for added corrosion resistance. They are available in various lengths with a wide range of thread types and strength grades. Some bolts are also designed for specialized uses such as flange nuts, coupling nuts and jam nuts.
Using the right type of fasteners is critical to ensuring your project is secure and that the parts will remain together for the duration of their lifecycles. It’s also important to be aware of the tensile strength, proof load and yield strength so you can choose the most appropriate hardware for your job. The tensile strength is the amount of pressure that the fastener can hold before it breaks or loses its elasticity. The proof load is the maximum load that the fastener can endure under a given condition and is tested under laboratory conditions to ensure it won’t fail in normal usage.
The thread size is another essential piece of information that you need to know when choosing the proper bolt for your application. This measurement is usually found on the nut or bolt’s head and is typically indicated by an OD number and a TPI or thread pitch number. The OD is the actual diameter of the bolt and is measured with a caliper, which is a tool that can take very precise measurements. The TPI is the number of threads that make up one inch and can be either coarse or fine.
There are a few common thread specifications that you will see on bolts and screws, such as UN, UNEF, and ISO. These specifications are meant to help you distinguish between standard and metric thread sizes and the different strengths that each has. Generally speaking, coarse threads are more rugged while fine threads are designed for higher-quality finishes.
Most people have a good idea what to expect from a standard hex bolt, but there are many other varieties of fasteners that require unique measurements callouts. For example, wing nuts are much different than regular hex bolts and need to be specified in terms of their shape. Similarly, coupling nuts and lock nuts have specific dimensions that set them apart from other hex bolts.