What Are The Dissimilarities Between A Hex Cap Screw And A Hex Bolt?

Posted by Lucifer Smith on April 14th, 2021

The most fundamental difference between these screws is how you install these fasteners. The machine screw manufacturer offers various types of fasteners. These screws have different purposes, uses and shapes, and sizes. However, machine screw suppliers can guide you about various types according to your benefit.

The variations between these two fasteners are fairly substantial both from a manufacturing and dimensional perspective and an application standpoint. Generally, people use hex cap screws in precise applications such as an OEM setting where tight tolerances are essential. Moreover, machine screw manufacturer specifies Hex bolts when the mechanical properties are more critical than dimensional tolerances; for example, the construction industry. For sample, the manufacturer provides SAE J429 Grade 2 as a hex cap screw; however, ASTM A307-A is a standard hex bolt specification.

Below is an overview of the specifics these fasteners are required to meet.

Hex Cap Screws

• The flat washer is facing under the screw head that meets specific tolerances like described under ASME B18.2.1-1996.
• The manufacturer will usually make hex caps by a cold-heading process like large standard sizes or turned CNC operation.
• A radius is under the screw head at the shank.
• Body screw diameter of plus nothing, minus .011″ for a 1-1/4″ diameter cap fastener.
• The typical bolt is industrial, manufactured by hot-forging process.
• Some mutual fastener specifications unless then specified: ASTM A449 and SAE J429 Grade 2, 5, and 8.
• A die seam diagonally the bearing surface is allowable.
• Allows a condensed body diameter to be not less than the minor pitch diameter of the thread.
• Some standard machine screw specifications unless otherwise specified: A354, ASTM A307A, and F1554.

Hex Bolts

The list is not inclusive but signifies some of the differences between these two machine screw designations. There is flexibility to use other grades, materials, and bolt standards as settled by the manufacturer and purchaser. Thus, be cautious when ordering bolts; make sure you are clear about either your project needs cap screws or bolts.