How to choose socket wrenches: drive, size and profile

To choose a socket you need to know three things: the drive size of the ratchet or driver (1/4, 3/8, 1/2 or 3/4 inch), the nut size in millimetres, and how far the screw protrudes, which decides whether you need a standard or a deep socket. In the collection the sizes range from 6 to over 20 mm and the lengths from 25 to about 390 mm. If you use it with an impact wrench, a chrome socket is not enough: you need an impact socket.

The types

• Hexagonal sockets: the six-sided profile wraps around the nut and grips it well on the corners. They are available in standard and deep series, such as the Fervi standard-series hexagonal socket.
• Polygonal (bi-hex) sockets: a multi-point profile that lets you engage the nut in more positions. They also come in standard and deep series, for example the Fervi standard-series polygonal socket.
• Spark plug sockets: shaped to fit the spark plug seat, such as the Stanley spark plug sockets with 3/8 inch drive.
• Socket sets and series of wrenches: several sizes in one case, for those who do not know in advance which screw they will come across.
• Adaptors and universal joint: used to change the drive size, for example from 3/8 to 1/2, or to work at an angle.
• T-bar and spinner handle wrenches: sockets with a right-angle handle, for nuts in awkward positions.

How to choose by job

The features to look at

• Drive: the square drive that engages in the ratchet. In the collection you will find 1/4, 3/8, 1/2 and 3/4 inch. The small drive is for small screws and tight spaces, the large one for large bolts.
• Size (mm): the nut size, from 6 to 19 mm and beyond. It must be exact.
• Opening (mm): shown in the data sheets with values from 8 to 22 mm. As with the size, it must match the nut exactly.
• Length (mm): from 25 to 390 mm. The longer it is, the deeper it can reach a recessed nut; the shorter it is, the easier it is to handle.
• Finish: chrome-plated (also polished), nickel-plated or satin. It protects against rust and cleans easily.
• Standards: some data sheets cite DIN 3124, ISO 1711-1 or ISO 2725-1. They are useful if you need to buy tools that comply with a specific standard.
• Weight: from a few grams to about 0.2 kg for a single socket: it matters when you work for long periods.

Common mistakes

• Using a chrome socket with an impact wrench. It can split. For the impact wrench you need impact sockets.
• Choosing the wrong drive. A 1/2 inch socket does not fit a 3/8 ratchet: you need an adaptor, which however adds a weak point.
• Pulling in jerks. The handle must be pulled smoothly, otherwise the socket slips and ruins the corners of the nut.
• Choosing the size by eye. A slightly larger socket fits loosely on the nut and rounds it off.
• Using a standard socket where the screw protrudes. If the nut is at the end of the thread, you need the deep one.

Frequently asked questions

Hexagonal or polygonal socket: which should I choose?

The hexagonal one grips the corners well, so it is the choice for very tight nuts. The polygonal one engages in more positions, so it is useful when you have little room to turn the wrench.

What drive should I buy?

The one that matches the ratchet you already have. For general workshop use the most common choice is between 3/8 and 1/2 inch; 3/4 is for large bolts, 1/4 for small screws.

Can I use the socket with a drill or driver?

It depends on the type of driver. With impact wrenches you need impact sockets; chrome ones are designed for hand use.

Set or single socket?

The set for those who work on different screws, the single socket to replace the one that wears out most.

You will find all the sizes in the socket wrenches collection: if you do not know which drive or series you need, ask for a quote or advice from the AMES technicians.