The Different Types of Bolt Heads and Their Uses

Types Of Bolt Heads

Bolts and screws come with numerous head shapes designed for use with the tool or means intended for tightening said fasteners. Furthermore, these head configurations are not just design considerations they also express the way the fasteners interact with tools to apply torque.

Some common types bolt heads that are in much use today are square, hex, slotted hex washer, and socket caps.

Square heads are traditional. Typically, the head is a square shape, followed by a shaft, and when torque is applied, the shape resists rotating.

Square heads are practical integrally design and reasonably effective. Square bolts are still available, but due in part to previuosly mentioned factors, hex heads now dominate square heads in many applications.

Hex heads are now more dominant than square heads. They are designed to be engaged by wrenches or spanners, and the wrench varieties utilize the gripping surface to put more torque on the nut or combination of nut and bolt, greater than square heads.

The six-sided shape of the head allows for an easier interface for the wrench. The shape provides more options for precision in applied torque which is one reason why hex heads are preferred shapes in applied assembly and route mechanical work today.

There are numerous other head shapes in use as well, namely:

#1. Flat Bolt Head.

This is the style you will generally see when there is a need for the bolt to sit flush with the surface – nothing sticking out. It has a flat top, and a countersunk design which means it is made to sink into the product you are fastening.

This way, you have a clean, smooth finish. Flat heads are generally used when a low-profile look is preferred aesthetically or functionally.

#2. Oval Bolt Head.

This can be thought of as a cousin to the countersunk flat head. It is also countersunk but has a slight rounding on top, without being a classic round head. It has the same benefit of being flush with the surface, but adds more flair than a flat head, because it has an oval contour.

You’ll commonly see these used in applications where looks matter or where you want the low-profile result but a softer look.

#3. Pan Bolt Head.

This one is all about slight convexity. A pan head has a gentle round top and short straight sides. It is not as flat as the flat or oval heads, however it is not a true dome either.

These are quite popular in cases, where appearance is part of the equation, like furniture or fixtures, because of the decorative elements without being overly exaggerated.

#4. Truss Bolt Head.

Truss heads have an unusually large, round top. Designed to disperse force, they are used in structural or construction jobs where keeping things tight is essential.

You will regularly see truss heads used in truss systems, or applications where large material needs to be secured tightly. The large surface also protects the materials, as the wide surface spreads out the holding force while giving a decent amount of holding force.

#5. Round Bolt Head.

As the title implies, this style is all about shape – a fully rounded head that is primarily “form” over “function”. Rounded heads may not be the most typical head shape for industrial applications, but of all the heads, they cover the bases of a more decorative look. Think of them more as the “finishing touches” bolts that serve a purpose.

#6. Hex Bolt Head.

Most people probably are familiar with this type of bolt head. The six-sided, hexagon shape is simple to grab with a wrench or socket, and it allows you to exert lots of torque while tightening or loosening.

The hex head is so efficient and easy to use that it can be found everywhere; from construction and automotive work to machinery and home projects.

#7. Hex Washer Bolt Head.

Above is the hex head with an attached washer underneath. The washer is a stressing distributing surface used with bolts to help reduce wear and eliminate damage to the material it attaches to.

This is an efficient design that spares you the need for one more hardware piece when you need a bolt to act as a pin; it is a common choice for situations when you want a simple, reliable installation.

#8. Slotted Hex Washer Bolt Head.

This variation is an advancement on the hex washer concept, as it includes a slot in the head. This feature allows you to use a screwdriver rather than a wrench, which is great to have in some tighter spaces.

You have the packet-sized advantages of load distribution from the washer, in addition to the versatility of two tightening types.

#9. Socket Cap Bolt Head.

Socket cap bolts are characterized by a relatively clean and cylindrical body shape that features a recessed hex opening specifically designed for use with a socket driver.

They provide a nice, sleek, compact shape and are useful when you need to provide strength with a fastener that does not have a substantial head sticking out.

Because of the ability to support high torque and linear direction fastened, socket caps can often be found in precision applications such as machinery or electronic assemblies.

#10. Button Bolt Head.

Button heads are like a simpler version of a bolt head. They are low-profile, smooth, round fastener heads that have a shallow domed top and hex socket drive.

Button heads are great when the intent is to achieve a clean look and to not have the fastener be a focal point. Think of a button head as being slightly more refined private socket cap bolt, it’s slightly less rugged, but is just as effective for lighter duty applications.

While there are many similarities between bolts and screws, there are also some differences.

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