What is a tap bolt versus a hex cap screw?
Tap bolts and hex cap screws are both types of hex bolts, which have a hexagonal head and can be installed using a wrench. However, key differences exist between the two that make them suitable for different applications.
Tap bolts are fully threaded, meaning the threads extend along the entire length of the bolt. On the other hand, hex cap screws are only partially threaded and have a shoulder, which is an un-threaded section between the head and the threaded portion of the bolt.
How do you know when to use a tap bolt versus a hex cap screw?
When deciding whether to use a tap bolt or a hex cap screw, you need to consider a few factors. Hex bolts typically start at 1/4" diameter, and smaller diameters, known as machine screw sizes (#4 - #12), are referred to as trim head hex screws. Both of these have full threading. Shorter hex cap screws also have full threading, while longer ones possess a shoulder. To determine the amount of thread on a hex cap screw, you can use the formula: (2 x diameter) + 1/4". If the hex cap screw is longer than 6 inches, the formula would be (2 x diameter) + 1/2".
One important consideration is the amount of support and tensile strength required for your application. Hex cap screws offer more support because the cross section at their shoulder is larger than the cross section at the threaded portion of a tap bolt. The shoulder of a hex cap screw provides additional tensile strength. Therefore, if you need a bolt that can handle greater loads and provide more strength, the hex cap screw would be the preferable choice.
On the other hand, tap bolts can be a good choice when you need to fasten through a significant amount of material. They are also suitable when you are uncertain about the exact thread length required for your application. Tap bolts are commonly used in fastening motors to machinery, making them popular in the automotive and truck repair industry. They are also useful for adjusting belt tension in pulleys. Overall, tap bolts tend to be more versatile than hex cap screws.
Final Notes on Tap Bolts and Hex Cap Screws
It's worth mentioning that there are various materials and finishes available for both tap bolts and hex cap screws. These include stainless steel, LCS plain, zinc, hot dipped galvanized, as well as domestic, titanium, brass, silicon bronze, and nylon, among others. You can choose the appropriate material and finish based on the specific requirements of your project.
In summary, use a hex tap bolt when you need to thread through a substantial amount of material or when you are unsure about the thread length needed. Tap bolts are versatile and commonly used in various industries. On the other hand, choose a hex cap screw when your application requires extra tensile strength and greater support.