What socket sizes are available?

     
     
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 Two 13mm sockets, one with a 1/2" drive socket and the other with a 1/4" drive socket 

Socket sizes are determined by the size of the socket head and the size of the drive socket i.e. a 13mm socket with ¼" drive. 

 
     
 3/4" Drive socket 

Although socket heads are available in both metric and imperial sizes, the 'drive socket' size of a socket is always imperial. This is due to it being an international standard to which no metric equivalent exists.

 
     
 Sockets are sized either metrically or imperially, some of these can look very similar in size such as 13mm and 1/2" sockets 

Socket heads are available in either metric or imperial sizes, depending on whether they are designed to be used with metric or imperial fasteners. 

 
     
   Wonkee Donkee says: "You should always use the correct type of socket for the fastener you want to turn. Using an imperial socket on a metric fastener or vice versa is likely to round the fastener head." 
     
 Vernier caliper 

You can find out the head size of a bolt by measuring across its flats with a vernier caliper (see our page:  What is a vernier caliper? for more information). However, a quicker and easier way is often to simply try placing various sockets on the head of the fastener until you find the one that fits. This is also the only way to tell the size of fasteners such as Torx and E Torx that do not have easily measurable dimensions.

 
     
 Metric 65mm socket 

Metric sockets are most commonly available in head sizes starting at 3mm.

 

Imperial sockets are most frequently sold in head sizes starting at 5/32".

 
     
 Socket head sizes are measured across opposing internal walls 

The size of the socket head denotes the size of the socket and can be either imperial or metric. The socket head size is measured between opposing internal walls.

 
     
   

Where can this information be found?

 
 The size of a sockets head is imprinted on the outside of the socket for easy identification in this case 65mm 

Sockets have the socket head size either stamped into the side of the socket, or laser etched onto the side for easy identification purposes.

 

Laser etching is more commonly seen on sockets that have a black oxide surface finish such as impact sockets.

 
     
   

Drive socket

 
   

There are 5 different sizes of 'drive socket' that are commonly used: 1/4", 3/8", 1/2", 3/4" and 1".

 

The smaller the drive is, the smaller the head is likely to be as well. 

 
     
  

There are two main reasons for this.

 

1. A small socket is more likely to be used in a small or confined space, so having a smaller 'drive socket' enables a smaller ratchet or wrench to be used. 

 
     
  

2. A small fastener that requires a small socket, will not need as much torque applied to it in order to tighten or loosen it. This means that the drive will not need to be as strong and therefore large.

 
     
 Ratchets with longer handles are able to apply more torque but need a larger drive square to do this. 3/8" drive ratchet can apply more torque than 1/4" drive ratchet 

A large nut or bolt will require more torque to turn it. This means more force will be put through the drive square of the turning tool. A larger drive square is therefore required to prevent it from breaking.

 

Having a larger drive square means that the wrench or turning tool can have a longer handle/lever, which enables it to apply more torque through the socket to the nut or bolt.

 
     
 Two 13mm sockets, one with a 1/2" drive socket and the other with a 1/4" drive socket 

There is some overlap between the socket head sizes that are available with different sized 'drive sockets'. For example, a 13mm socket head size can be purchased with either a 1/4", 3/8" or 1/2" 'drive socket'. A 13mm socket is both one of the largest sockets available with a 1/4" 'drive socket', and one of the smallest with a 1/2" drive socket. 

 
     
  

Nuts and bolts around the cross over 'drive socket' size of socket sets, such as those requiring a 13mm socket are used in a wide variety of applications. Some of these applications can be in confined spaces that may require a small wrench, but they can also be used in other applications that would require much greater torque, and, therefore, a larger wrench with a larger drive square. 

 
     
 

'Drive socket' size

Metric socket head sizes available

Imperial socket head sizes available

1/4"3, 3.2, 3.5, 4, 4.5, 5, 5.5, 6, 7, 8, 9, 10, 11, 12, 13, 14mm5/32, 3/16, 7/32, 1/4, 9/32, 5/16, 11/32, 3/8, 7/16, 1/2"
3/8"5.5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22mm1/4, 5/16, 11/32, 3/8, 7/16, 1/2, 9/16, 5/8, 11/16, 3/4, 13/16, 7/8"
1/2"8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 30, 32mm3/8, 7/16, 1/2, 9/16, 5/8, 11/16, 3/4, 13/16, 7/8, 15/16, 1, 1-1/16, 1-1/8, 1-3/16, 1-1/4"
3/4"19, 22, 24, 26, 27, 28, 30, 32, 34, 36, 38, 41, 42, 45, 46, 48, 50mm 5/16, 1-1/8, 1-3⁄16, 1-1/4, 1-5/16, 1-3/8, 1-7/16, 1-1/2, 1-5/8, 1-3/4”
1"36, 38, 41, 46, 50, 54, 55, 58, 60, 63, 65, 67. 70, 71, 75, 77, 80mm15/16, 1, 1-1/16, 1-1/8, 1-1/4, 1-5/16, 1-1/2"
 
     
    Wonkee Donkee It may be possible to get sockets in sizes other than these. But they will likely be a specialist order item, that is not readily available. 
     
   

What about the size of the rest of a socket?

 
  

As well as knowing the socket head size and drive socket size, it can sometimes be necessary to know other dimensions of the socket as well. This is often the case if you need to reach a fastener that is located in a recessed cylinder. 

 
     
 They other key socket measurements are A socket end diameter, B Drive end diameter, C Bolt clearance depth, D Length, E opening depth 

The five other key socket measurements you may need to know are:

  • Socket end diameter

  • Drive end diameter

  • Bolt clearance depth 

  • Length 

  • Opening depth

 
     
 The socket end diameter is the external diameter of the socket head end 

Socket end diameter

This is the external diameter of the socket head end of the socket. It can sometimes be necessary to know this measurement if the socket has to reach inside a cylinder or recess.

 

Some manufacturers make thin walled sockets that reduce the socket end diameter slightly, allowing them to fit in areas regular sockets will not.

 
     
 Socket drive end diameter is the external diameter at the drive end of a socket 

Drive end diameter

This is the external diameter of the drive end of the socket. It is usually smaller than the socket end diameter on most sockets, however on some very small sized sockets the drive end diameter may be larger than the socket end diameter. This is why it can be important to know the drive end diameter, as when using very small sockets, if the fastener is recessed, having a larger drive end diameter may prevent the socket from reaching the fastener head.

 
     
 The bolt clearance depth is how deep into the female recess of the socket the shaft of a bolt can travel 

Bolt clearance 

This is the internal depth of the socket that the bolt or fastener shaft can travel into before reaching the drive square of the turning tool. This can be important to know if the bolt shaft protrudes a long way above the nut you need to turn.

 

If the bolt clearance of your socket is not sufficient, then you may need to use a pass through socket instead see What are the different types of socket? for more information.

 
     
 Comparison of standard and deep size 13mm sockets 

Length

This is the total external length of a socket. It can sometimes be important to know this measurement, as some situations may need the use of a socket in a confined area and deep sockets may be too long for this. One example would be accessing the bolts on a scooter transaxle without removing the wheels.

 

Some manufacturers make mid-length sockets for rare situations where a socket longer than standard is required but the area the fastener is located means that a deep socket (deep sockets are longer than standard sockets) will be too long to fit.

 
     
 Socket lengths, Deep length socket set, Mid length socket set, Standard length socket set 

Sockets are available in standard and deep lengths, while some manufacturers also make mid length sockets that are longer than standard sockets but shorter than deep sockets. For more information see  Why is a socket's length important?

 
     
 The opening depth of a socket is how far the head of the bolt will travel into the female recess of the socket head 

Opening depth

This is the internal depth of the socket that the bolt or fastener head can travel into. Deep sockets have a much greater opening depth allowing the bolt head to travel up into the socket. You may need a socket with a longer opening depth if you need to turn a nut on a long bolt shaft.

 
     
 The wall thickness of a socket is the thickness between the internal walls of the socket head and the outside of the socket head 

Wall thickness

The wall thickness of a socket is the thickness between the outer edge of the socket head and the internal walls of the socket.

 
     
 Warning thin walled sockets are not as strong 

Some deep or long-reach sockets will have a thinner wall thickness than other sockets in order to reduce the total diameter of the socket, enabling it to fit into narrow recesses easier. This does however weaken them so they should only be used if a normal deep or long reach socket is unable to reach the fastener, if it was located in a narrow cylinder for example.

 
     
 A narrow chamfer angle on a socket makes it easier to locate on a fastener. A wider chamfer angle allows you to apply more torque and reduces the chance of rounding the fastener head. 

Chamfer angle

The chamfer angle is the angle of the chamfer that is put on the end of a socket.

 

The narrower the chamfer angle, the easier it will be to locate the socket onto the head of a fastener. 

 
     
 Wider chamfer angles increase the contact with the fastener head reducing the chances of rounding the fastener. But they can be harder to locate onto a fastener. 

However, having a narrow chamfer angle reduces the contact area between the socket and the fastener, which increases the chance of rounding the fastener head (when a socket applies too much torque to the corners of a male fastener head and deforms it and reduces the torque that can be applied to it.

 

For more information on rounding a head, see:  Rounding a head - Rounding the head of a fastener (or rounding off) is when a socket applies too much torque to the corners of a male fastener head and deforms it. This results in the head of the fastener losing its flat-sided shape and becoming round.

 
     
 Socket product specification 

Where can these sizes be found?

While the main sizes of a socket, head size, drive size and length are usually included in the description advertising the socket, many other sizes may not be. These will however be included in the product specification or data sheet for the socket. 

 
     
 Checking the manufacturers website for socket product specification 

You should be able to obtain a copy of the product specification or data sheet from the retailer or they can often be found on the socket manufacturer's website.

 
     
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