In the world of fasteners there are so many options, it could make your head spin. First you have the material the fastener is made of, then the platings, coatings and any other treatment that is applied. Of course there are different sizes to accommodate various applications and different methods of threading (in the case of bolts and screws) for strength. Speaking of bolts, there are even different shaped heads that work best for different applications and industries. A square head bolt is common in the railroad industry, on electrical panels and in furniture manufacturing. Hex head bolts are found across the building industry and in countless other common applications.
So what’s the difference between these two fastener styles? Besides the head shape, the main differences are found in the applications and benefits of each style.
Hex Head Bolts
Hex head bolts are made with a six-sided head. This common shape is easily worked on with everyday tools, making it ideal for industries where speed and versatility are important.
Nuts are often found in the hex shape as well, meaning there is always an easy match found for hex head bolts.
Square Head Bolts
A square head bolt has a distinctly shaped head that makes it ideal for working in blind areas. With the proper tools, tightening a square head bolt is easy even when the fastener is out of your line of vision.
This shape of bolt head is also easy to check visually. The flat sides make it simple to gauge whether the bolt has been properly tightened, since the sides will align with the materials being fastened. (This worked really well in the railroad industry, where supervisors could check that all bolts were on based on whether the head lined up with the tie.)
What Are the Advantages of Each Type?
Hex head bolts are a good overall choice for typical fastener applications. Choose a square head bolt if the fastener location is difficult to see or very small (such as those seen in electronics). Be sure to choose a matching nut and take into account the materials and coatings that meet the strength specifications of your project.