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Keys and sockets buying guide

Guide written by:
John, DIYer & IT developer, Brighton

John, DIYer & IT developer, Brighton

59 guides
Box wrenches, pipe wrenches, eye wrenches, socket wrenches. The choices can be difficult to navigate. Many will catch your eye but do you know which to choose? A small collection is easy to maintain, or you can let yourself be seduced by any and all options.

Important features

  • Bolts
  • Nuts
  • Flat
  • Mixed
  • Pawl
  • Hexagonal
  • Wheel

How are they differentiated?

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Picking the right wrench, key or socket can be difficult with such a wide range available. This guide will help you to determine which one is best suited to your intended use. Common sizes for bolts range from 4mm to 10mm for small projects, from 10mm to about 23mm for routine work, and well beyond that for large scale work.

  • Box wrenches have one or two forks, one on each end, each of a different size. For example, One fork might be 4 mm and the other fork 6 mm. Because of their small profile, they are ideal for nuts and bolts that you might have difficulty accessing with another tool. Essential in plumbing and mechanics.
  • Eye wrenches, which, unlike the box wrenches, exert their force on the 6 sides of the nut. They now exist with ratchets, which are still compact on high-end models.
  • Mixed wrenches that are represented with a box wrench on one side and a closed wrench on the other. Convenient!
  • Adjustable wrenches are box wrenches whose fork width is adjustable by means of a screw. Very practical to cover several nut sizes or atypical sizes with one tool. They are heavier and cumbersome. The play of the jaw limits the clamping force.
  • Lug wrenches are heavy duty and ‘L’ shaped. Think of a tire-iron and you’ll have the idea. The longer arm allows you to exert more force. You could also slip a pipe onto the end to extend the handle length and increase the torque even more.
  • Pipe wrenches are similar the adjustable wrenches. Rather than a smooth adjustable fork, pipe wrenches often include teeth to help with gripping a pipe. These wrenches come in a wide range of sizes depending on the scale of your project and can quickly become very heavy. To help improve torque, some models will include a second handle at the top of the wrench so you can more easily use two hands.
  • Socket wrenches work on all six sides of a nut or bolt similar to a eye wrench. Rather than working perpendicular to the nut or bolt, like most wrenches do, socket wrenches are tube shaped and fit over the top. Tightening a bolt is easy, but when tightening a nut you must account for the length of bolt that is revealed. Sockets of different lengths are available to accommodate smaller or shorter bolts. These sockets can often be attached to electric screwdrivers or drills.

Torx and Allen keys

Allen keys, hexagonal male, also known as hexagonal or BTR, and Torx keys (star-shaped) are found more and more in furnishing or mechanics, for example on bicycles. Their L-shape allows access to a deep screw and/or to exert a greater clamping force. The usual Allen key sizes range from 4mm to 10mm and the Torx from 10mm to 50mm.

0mm and the Torx from 10mm to 50mm.

Why take all the sides of the hexagon?

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Eye, lug, or socket wrenches enclose the six sides of the hexagon. In this way, the clamping force is distributed over the entirety of the bolt. The tool and the bolt wear less.


There are 6-sided wrenches to apply heavy force without damaging the nut or 12-sided to reposition the tool more quickly and easily. Some wrenches offer a mix of both.

You said ratchet?

The reversible ratcheting mechanisms present on the socket wrenches and the eye wrenches offer significant time saving by allowing the tool to be manipulated without disengaging it from the bolt for screwing and unscrewing. They are designed, unless otherwise specified by the manufacturer, for tightening or loosening without exerting excessive force or shock. Otherwise you risk damaging the ratchet.

Will it be enough to disassemble everything?

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It’s important to understand that one cannot use brute force or hammer a fluted nut with a ratchet The pro brands hold quite well, however, a tube wrench is better suited. Also, a bushing mounted on a ratchet does not make it possible to work on the bolts which are not easily accessible. Fortunately, many accessories are available to help you. Like the sockets, the accessories are fixed by a square box locked by a ball mounted on a spring. The most common nesting sizes, expressed in inches, are 1/4, 3/8 or 1/2. We can find 3/4 or even 1 inch for XXL sleeves.

Focus on accessories

  • Extension:  allows you to reach a bolt located in a tight spot or to avoid obstacles that would hamper the stroke of the key.
  • Cardan:  offers the possibility of operating on a bolt whose screwing axis is not strictly perpendicular to the plane in which the key is manipulated.
  • Reducer: for mounting a small fixing sleeve on a larger one, or vice versa, eg from 3/8 to 1/2. They are very practical for mixing different sets of sleeves.
  • Tip Holder: For mounting any hexagonal tail screwdriver directly on a socket wrench or using the above accessories

If I understand correctly, there is no ratchet for flat keys?

The flat wrenches do not always have a ratchet. Some are fixed and must be disengaged to adjust their position. Some do have ratcheting, you have to pay attention to whether you are tightenting or loosening with these. Others still offer both options and can be switched from one to the next at your convenience.

If I push it hard, will it be able to stand the force?

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The forces exerted on the wrenches and bolts can be considerable. If you need a lot of force, consider purchasing hard metal tools (hardness varies from 42 to 50 HRC). Refer to the manufacturing standards that the manufacturer claims (DIN, ISO, DIN ISO or NF ISO) that define a minimum level of quality. They define the hardness of the metal and the amount of torque the tools can resist. Chrome Vanadium alone is not a sufficient guarantee. The quality of manufacture is also reflected in the shape and precision of the bore that will catch the hexagon. An adjusted bore and some optimized shapes transmit maximum force while preserving the hexagon. Know that the best distributors guarantee their keys for life Soon broken, soon replaced. Spending a little more money and time on your selection can save you both in the long run.

What are torque wrenches used for?

There are applications where the clamping force must be metered. If the tightening is too loose, the assembly may not hold which has serious consequences. Imagine a bicycle’s handlebars coming loose mid ride. If tightened too far, there is a risk of breakage of the screw or deformation of the tightened parts. Models that allow you to meter the force are very simple to use. Mount the socket of the correct size, set the torque expressed in Newton meters, and then go at it. Their use is mainly in precision mechanics.

How do you find yourself in the middle of it all?

You can buy according to your needs. The key sets are much cheaper than the kits. If a given key is often used for important jobs, invest in a quality key. Otherwise, a socket box and a wrench will meet most of your needs. A set of box wrenches also makes sense.

For do-it-yourselfers who are curious about their craftsmanship and are keen on choosing accessories and tools related to screwdriver bits, follow the advice of our editors and discover their guides:


And to work safely:

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Guide written by:

John, DIYer & IT developer, Brighton 59 guides écrits

John, DIYer & IT developer, Brighton

Since I was a child, I was always interested in manual and technical works. Always fascinated by woodworking, I took advantage of my first flat as a playground. On the cards: electricity (of course, safety first!) and some partition walls; but also decorating with the help of the missus, made-to-measure furniture and little tricks to optimise the space, all the while remaining as original as possible. When the little one arrived, I started building bits and pieces for him!

Lacking space, I have not got a permanent workshop and certain tools I dream about but are not part of my collection. Not to worry, I already know a lot about DIY and I have a high-tech profile that I hope will guide you in your decisions!

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