Screw Head Types and Styles

Screw head type, or style, is determined by the size and the shape of the screw head.

Screw head size

The height of the screw head is measured vertically from the underside of the head's bearing surface, where the screw shank ends, to the top of the screw head.

The screw head is also sized by its diameter.  The diameter of the screw head is usually greater than that of the screw shank.

​Since a screw head is typically cylindrical or conical it makes sense that the height and diameter are the causal characteristics of the type of screw head.  The volume of a cylinder or cone are determined by the height h and radius r (radius is 1/2 of the diameter). 

Screw head shape

Screw head shape is important not only for aesthetics, but also for the mechanical properties of the screw. A screw head type with a greater head diameter to shank thread diameter provides a greater bearing surface.

Head shape makes a screw more susceptible or more resistant to tampering.  If you're designing a prison, you'd want to use screw heads with a low profile that made them harder to grasp and unscrew.

The shape and size of a screw head dictates how much torque can be applied to a screw.  Tall screws accept longer drivers which provides more torque.  Button shaped heads have less driving surface than pan shaped heads and are harder to screw or unscrew.

Countersunk/Flat

A countersunk or flat head screw can be driven flush with the connecting surface material. You will commonly find wood screws have countersunk heads. First use a countersinking drill bit to carve out space in the connecting material to allow the screw to be countersunk.  The connecting material must be thick enough to allow a screw to be countersunk.

Oval Countersunk

Just as exposed wood beams or exposed brick is sometimes desirable in industrial design, so too are exposed screws.  An oval countersunk screw can be countersunk, but the head is not flat.  A low-profile(short) rounded head protrudes above the connecting surface for decorative purposes.

Round

A round head is a general use screw head.  It can be used almost anywhere in a pinch - it's the utility player of screw heads.  A round head that is dome shaped provides a decorative look and a good bearing surface.  It has a deeper slot for driving.

Pan

Pan head screws have a large diameter and a low height, like an upside down frying pan (hence the name), and are not rounded like a bowl. The outer sides are straighter than in a round head, and the slot isn't as deep as that in a round head because the head height is shorter. The top of a pan head screw is usually flat (again, like a frying pan). Pan head screw heads combine the properties of truss, binding and round heads.

Truss

A truss head type screw is also called oven head or stove head. This is wide head type that provides hold of thin materials.

Securing cabinets to walls, especially into steel studs, is a common application of truss head screws. Other uses include securing parts that need to move past one another as the low height of a truss head screw gives increased clearance between parts. 

Button/Dome

A button head screw has a cylindrical head with a rounded transitioning to flat top.

Fillister and Cheese Head

Fillister and cheese head style screws are tall and narrow, making a cylindrical shape.  The height of the head is about half the diameter.  The tall head allows for deep drive slots and a lot of driver to screw contact when driving, which can generate more torque.

A cheese head has a flat top.  A fillister, or raised cheese, head has a rounded oval top.  A fillister head has a greater height to diameter ratio than a cheese head.

Binding

The binding head type screw is used to bridge wires and other electrical connections.

Hex

Hex head screws have 6 sided heads and no driving slot.  They can be driven with a wrench.  They typically have a washer built in.

Hex heads can handle more torque than other types of heads, making them useful when using air tools to drive screws or bolts.

Square

A square head screw has a 4 sided head and no driving slot.  Its usage is similar to that of a hex head screw - drive with a wrench and can survive higher torque without breaking.

Wafer

A wafer head has an underside bearing surface shaped like a countersunk screw.  The difference between the two is that the sloped underside of a wafer head screw doesn't extend all the way to the edge of the screw head like a flat countersunk head.

Wafer heads provide more bearing surface than flat heads.

Bugle

A bugle head is shaped like the bell of a bugle. Bugle heads distribute the bearing force over a greater surface area than a flat screw, lessening the pressure.  Bugle heads are used in drywall screws.

Socket Cap

A socket cap head is cylindrical with a socket cavity that accepts a driver.