What is a hex socket?

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 Hex socket and in-hex socket comparison, hex sockets fit over the head of fasteners, in-hex sockets fit inside the head of fasteners 

The term 'hex socket' refers to a socket that fits around the outside of a hexagonal fastener head. However, its use has broadened and it is now sometimes used to refer to any shape of socket that fits around the outside of a fastener, instead of locating into the fastener head.


6 point hex sockets

 Hex socket 

A 'hex socket' is a socket designed to fit the head of a hexagonal fastener such as a nut or bolt. 

 Points of a 6 point socket 

Hex sockets are also referred to as '6 point' sockets as six points are formed where the internal walls from the hexagonal recess meet. 

 Better quality sockets have curved internal walls. Curved internal walls of the socket head move the contact point away from the corners of the fastener, More torque can be applied to a fastener without rounding it off as a result. 

Better quality hex sockets have internal walls that are slightly curved. This helps apply the torque from the socket to the flats of the fastener instead of the corners, which reduces the chance of rounding the head of the fastener. This also means that more torque can be safely applied to the fastener by the socket, allowing them to to tightened more or screwed into harder materials such as metal or hard woods.

 6 points of an E Torx socket, Regular 6 point socket 

What is meant by regular 6 point?

When a socket is referred to as being a "regular 6 point" it means it is a 6 point hex socket. This term is sometimes used to avoid confusion with E Torx sockets that also have 6 points.


12 point bi-hex sockets

 12 point or bi-hex sockets are so called because the female socket head recess is shaped like a bi-hexagon and forms 12 points where its internal walls meet. 

A 'bi-hex' or 'bi-hexagon' socket is also called a 12 point socket. This is because twelve points are formed where the internal walls of the recesses intersect.


The name 'bi-hex' comes from the internal shape of the socket recess being that of two hexagons laid over one another.

 12 point or bi-hex socket can be used on a hex 6 point fastener as well. They may also be used to turn square 4 point or 8 point fasteners. 

Just like 'hex sockets', 'bi-hex' sockets can also be used to tighten or loosen hexagonal shaped fasteners, but they have a couple of advantages:

  • They are able to fit 6 point fastener heads in twice as many positions as a regular 'hex socket'. This means it is easier to locate the socket onto the fastener in tight spaces.

  • They can also be used to turn square (4 point) and bi-hex (12 point) fastener heads as well, giving them greater versatility. 

 A square head fastener will not fit inside a hex socket but will fit a bi-hex socket 

The bi-hex shape allows the socket to fit over the head of squares fasteners, unlike a regular hex socket.

 Bolt head that has been rounded off by too much torque being applied to the corners of the bolt head. 

However, a bi-hex socket will apply the torque closer to the corners of a 6 point hex head fastener, which means the chances of the fastener head becoming rounded are greater.


Hex socket sizes

 Sockets come in made different sizes, 5mm socket and 65mm socket 

Socket head

Socket heads can be measured in both metric and imperial units. Metric socket sizes can range from 3mm to over 80mm, while imperial socket sizes range from 5/32" to over 1-½".

 13mm sockets with different drive sizes, 13mm socket with 1/4" drive and 13mm socket with 1/2" drive 

Drive socket

At the other end of the socket is the drive socket, which is used to attach the socket to a ratchet, torque wrench or other type of turning tool. Unlike the head of hex and bi-hex sockets, which is available in both metric and imperial sizes, the drive socket is always sized in imperial measurements. The most common sizes are ¼", ⅜", ½", ¾" and 1".


Other types of hex socket

 Confusingly hex socket is a term that is sometimes used to refer to any socket that fits over a fastener head. 

With the increasing variety of sockets, the term "hex socket" is often used to describe any socket that fits over the head of a fastener instead of fitting into the fastener head, as with a socket bit. This is despite many of these new forms not having a hexagon shape to them.


Other types of hex socket include:

 8 point sockets are now considered a specialist item as 12 point sockets can often do the same job 

8 point and square sockets

Whilst it still may be possible to get an 8 point or square socket, they are now considered a specialist item that is often only made to order in the size you specify, as 12 point sockets will usually be able to do the same job.

 E Torx sockets are sockets designed for turning external torx fastener heads  

E Torx sockets

E Torx, or 'external Torx sockets' to give their full name, are sockets designed to fit and turn fasteners with an external Torx head.


E Torx sockets are sized from E1 (smallest) to E100 (largest), although most E Torx socket sets will range in size from E4 - E24. Like standard sockets, they have a square drive for attaching a turning tool that can range from ¼" - 1" in size.

 E Torx bolts allow more torque to be applied than Hex or Bi-Hex bolts 

E Torx sockets and fasteners can apply more torque than regular hex or bi-hex sockets without damaging the fastener head. This is because of the greater contact area between the socket and the fastener head, along with the fact that more of the torque is applied away from the corners of the fastener head, so there is less chance of it rounding off.

 E Torx fasteners are often used on car engines, E Torx fastener heads used on an engine 

E Torx are often used in areas where high torque and clamping force is required.


One of the most common places to find E Torx fasteners is on the cylinder head bolts of car engines.

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