Inch bolts are a common fastener found in many projects and applications. These bolts are typically made from Steel and can be Hot-dipped Galvanized, Stainless, Chrome or Nickel Plated to increase corrosion resistance. These bolts are available in a variety of sizes to suit different applications and materials. To determine what size bolt you need for your project, there are a few key measurements you will need to know. These include the Bolt Diameter, Thread Pitch and Length. If you know these measurements, you can take them to your local hardware store and purchase a bolt that matches your needs.
To make sure you are purchasing the right sized bolt, it’s important to understand the numbering system used on Inch threaded fasteners. The full designation is generally displayed on the head of the bolt in a circle: OD, TPI and L. OD is the overall diameter of the bolt and can be determined by measuring the distance between two opposite crests or topmost surfaces of the bolt thread. TPI is the distance between one bolt thread’s root and the next, and is correlated with the bolt strength.
It’s also important to note that you should not mix standard and metric bolts. Both types have specific threads that are designed to work with correctly-mated parts. If you try to use a metric screw with a standard nut, the bolt threads may strip or damage the nut.
There are a few ways to identify whether your bolt is Inch or Metric, although most of these methods will require special tools. Some bolts will display an indentation pattern or numbers within the circle that indicate their strength grade, while others will have alphanumeric markings on their heads instead of or in addition to the line indentations. If the bolt’s mark has an “M” or a number followed by an alphabet letter, it is a Metric bolt.
If you are unsure of the measurement system your bolt is using, it’s a good rule of thumb to use a bolt diameter 1.5 – 2.5 times (up to three times for very thick materials) the thickness of the thinner material that the bolt is being used in. This will ensure that the bolt has adequate strength to hold the materials together, without risking the bolt failing due to shear or tensile stresses.
If you are working with a more sensitive material, it’s often best to use Coarse threaded hardware. These threads are thicker and more durable than fine-threaded bolts, making them less likely to gall and easier to install in delicate materials. They are also more tolerant to shear forces, making them an excellent choice for applications where the bolts will be subjected to abrasion. For this reason, coarse-threaded hardware is often preferred in paper binding and other non-metallic applications. However, this type of bolt should still be backed up with washers and face plates to protect the threaded surface from abrasion. The best material to use for this type of application is Stainless, which is an extremely tough and corrosion-resistant metal. Inch bolts