How do you know when to use a tap bolt versus a hex cap screw?
Tap bolts are fully threaded while hex cap screws are only partially threaded and have a shoulder. Both fasteners fall under the category of hex bolts, which refers to bolts with either partial or full threading and a hex head. Both installed using a wrench. How do you know when to use one over the other?
Hex bolts typically start at 1/4” diameter. Smaller diameters known as machine screw sizes (#4 – #12) are called trim head hex screws. Trim head hex screws have full threading. Shorter hex cap screws do as well. Longer hex cap screws possess a shoulder. To determine the amount of thread on a hex cap screw use this 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”. Here is an excellent spec sheet showing shoulder lengths of hex cap screws as well as the fully threaded lengths of hex cap screws.
Hex cap screws offer a lot more support due to the cross section at their shoulder being larger than the cross section at the threaded portion of a tap bolt. The shoulder of a hex cap screw provides more tensile strength. Therefore, when you need more strength you should choose the hex cap screw.
If you need a bolt to fasten through a lot of material, a tap bolt can be a good choice. Furthermore, they can be a safe bet when you don’t know exactly what thread length you need. Tap bolts work well for applications fastening motors to machinery so are popular in the automotive and truck repair industry. They also work well for adjusting belt tension in pulleys. Tap bolts are generally more versatile than hex cap screws.
Lightning Bolt carries tap bolts and hex cap screws in stainless steel, LCS plain, zinc, hot dipped galvanized, etc… We can also get you domestic, titanium, brass, silicon bronze, nylon, or any other special kind of tap bolt you may need. In summary, use a hex tap bolt when you aren’t sure exactly what thread length you need and/or need to thread through a lot of material. Use a hex cap screw when your project requires the extra tensile strength.