Often overlooked, the shape and geometry of the fastener screw head is a very important part of the fastener. Head geometry is the actual shape of the head where the drive interface resides. After all, the geometry of the fastener head can significantly affect the form, fit and function of the fastened joint.
most common head shape
Hex Head
Hex head screws are probably the most recognizable head type and are widely used in bolts. The hex head allows torque to be applied using a wrench on the outside of the head, so it differs from internal drive head types. This torque application is made possible by the opposing flat head surfaces on both sides of the bolt.
These are often found in "heavy duty" applications where fastening joints must have a high clamping force to function properly. Hex bolts do this because high torque can be applied directly to the hex pattern on the bolt head. The hex head can withstand a lot of torque ensuring the joint stays clamped together for long periods of time, meaning the bolt keeps the joint pre-tightened. These are widely used in engineering applications such as pressurized piping, pressure vessels and other fluid piping systems.
Hex Bolts
short hair
The head of the grub screw sits flat on the joint, creating a continuous surface on the part so the head doesn't protrude. These heads are sometimes referred to as "sunk" heads because they are designed to fit the matching countersunk profile on the fitting. These flats usually interface with countersinks and are angled at their head for a perfect fit with the interface countersink. The most common is the flat 100° screw head, which gets its name from the 100° countersunk angle on the screw head.
Flat head screws are used in carpentry consumables such as cabinets and woodworking applications such as wood floor or door frame mounting. This is because the parts must have smooth, flat surfaces as the parts slide against each other and there must be enough clearance to accommodate the movement. Medical equipment also uses grub screws, as many machines need to be cleaned and a flat surface is ideal.
flat head screw
pan head
Pan head screws are the most common type of button head screw, and probably the most recognizable type is the Philips drive screw. These screw types are round head screws only. They get their name because when they are secured within the joint they have a rounded nose protrusion and the side profile above the joint is actually a semi-circle. A pan head is similar to a button head, except it has tapered, truncated sides rather than a more rounded profile.
Phillips pan head screw
button head
This type of fastener head has a round head style that tapers to a flat interface so that the top of the screw does look like a button and the bottom of the button head fastener is flush with the fastened joint. These screw heads are typically used in internal socket drive configurations and have a recessed area to accept a matching drive bit.
Button head screws are not known for being used in high-strength applications, but rather for applications that require a wider bearing surface or a more refined appearance.
round head screw
Hexagon Cap
The head of this type of fastener is hexagonal cylindrical and can be tightened with a socket wrench. This design allows for easy access to the drive since the heads can be mounted flush with the surrounding material.
Socket head cap screws are used in stamping dies, injection molds, tools, machinery, furniture, and areas where strength and aesthetics are a priority.
Hex socket head cap screw with hole
This quick introduction opens the door to a vast world of fastener head types and configurations. MISUMI has a wide selection of fastener head profiles, you can explore them here.