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What are the parts of a socket?

What are the parts of a socket?

Different parts of a socket labelled

Knowing the different parts of socket is important to make sure you choose the right tool for the job. When working with different nuts and bolts it is important to use the right tool to get the most efficient result.

Socket Drive

Parts of a socket: the drive

The drive socket is the square hole which is used to attach the socket to a turning tool such as a ratchet or wrench.


Drive sockets can come in one of five sizes: 1/4″, 3/8″, 1/2″, 3/4″ and 1″. Unlike the socket head, drive sockets are always listed in imperial sizes. This is due to it being the international standard for which there is no metric equivalent.

Ratchet and Drive on a socket

  The drive socket size is a measurement of the distance between the flat sides of the square recess. The drive socket size must match the drive square size of your turning tool for the socket to fit correctly.


For example, a 1/4″ drive or 1/4″ square drive will attach to a turning tool that has a 1/4″ drive square.

Drive Socket Side Hole

Drive Socket Side Hole

The drive socket side hole is a small hole in the side of the drive socket.


A small spring-loaded ball bearing in the side of the turning tool’s square drive automatically locates into the drive socket side hole. This prevents the socket from falling off the turning tool to which it has been attached.

Drive Socket internal notch and side hole

Some sockets have an internal notch or groove inside the drive socket instead of a side hole. On these sockets, the ball bearing locates into the groove and serves the same purpose.

Socket Head

Socket head section

The socket head is at the opposite end to the drive socket and is the part that fits into (as with in-hex sockets) or over the fastener in order to turn it.

Socket head size is measured between 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.


Points on the internal wall of a socket

The points are the areas inside the socket head, where the walls of the socket meet. Most sockets have either 6 points (hex/hexagonal) or 12 points (bi-hex, bi-hexagonal). The number of points will determine what fasteners a socket will fit. 12 point sockets can fit a wider range of fasteners than 6 point sockets.


For more information see: What is a hex socket?

Internal Walls

Internal Walls of a socket

The internal walls of a socket head are the flat sides within it. On some sockets, these walls may be slightly curved. Better-quality sockets have curved internal walls that are designed to make contact with the head of the fastener on the flats (or lands), thus applying the turning force (torque) to this area of the fastener head.

Rounded bolt head which the inner walls of a socket grip

As the flats are stronger, it greatly reduces the chance of the fastener head being rounded off. 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). It also means that more torque can safely be applied to the fastener. Poorer quality sockets with flat walls apply the torque closer to the corners of the fastener head, thus increasing the chance of rounding it off.


For more information see: How does a socket work?

Stepped Collar

Stepped collars on a socket

Some sockets have a stepped collar to accommodate the difference in size between the drive square at one end, and the hex socket head at the other.

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