Types of keys

Wrenches are essential elements in our toolbox, both at home and professionally. However, many times we have keys that we never use because we are not sure what they are for, which is why it is worth analyzing them one by one in order to discover their usefulness.

We could define wrenches as manual tightening tools, since they are used to tighten screws and nuts of different sizes, which generally have an external or internal hexagonal shape. These keys are common in our homes, but also in small specialized workshops.

It is important to mention that they come in different measurement systems, so sometimes we must convert from inches to centimeters according to the European standard, while on other occasions it is necessary to convert centimeters to inches, especially in the case of cars and American gadgets.

There is a specific manual wrench for each task, so the result obtained in activities as diverse as repairing the car, adjusting a pipe or installing the best extractor hood depends on whether we have chosen the correct tool.

Classification of the keys according to the mouth

We can classify the keys into two large groups; fixed and adjustable. The fixed wrench is the most common in workshops at a domestic and professional level. It is a resistant steel tool made in one piece, so it can be used in jobs that require applying force in tightening. In this case, the mouth of each key has a specific measurement. For its part, the adjustable wrench has the particularity that it has an adjustable mouth, in this way, it is possible to modify the opening by means of a simple mechanism to adapt it to the size of the nut or screw.

The most common fixed keys 

Spanish Key

This is one of the most popular open end wrenches in the world, it is a straight tool that has an open U-shaped mouth at each end. Generally, the two mouths have different openings, so it is advisable to have a set of Spanish open-end wrenches to choose one depending on the size of the nut or screw. The most common measurements are from 6 to 32 mm, but it is possible to find wrenches with mouths of up to 50 mm.

star key

The characteristic that distinguishes a ring wrench is that it has closed jaws, therefore, it can completely embrace the nut or the screw head. Thanks to this, it allows easier turns and at the same time offers greater torque. It is very easy to recognize it, because it has 12-point star-shaped holes at the ends, which facilitate the adjustment of hexagonal elements.

Mixed key

This is a very versatile flat key, since it has an open U-shaped mouth at one end and a closed star-shaped one at the other, thus offering two options to adapt it to the needs of the moment. Combination wrenches are widely used in automotive mechanics and come with sockets of different sizes. 

offset wrench

Although it is a fixed key, it has a fundamental difference with respect to flat keys, since its structure is oblique, that is, it has an elbow shape at the ends, for this reason, the offset key is very useful for time to reach nuts and bolts in tight, hard-to-reach corners. In this case, the mouths are closed in a star shape for a better grip.

Ratchet wrench

It is a flat star wrench, but with the particularity that its closed jaws incorporate a ratchet system very similar to that of ratchet wrenches, which allows faster adjustment without having to reposition the tool many times. It is indicated for easy tightening of low torque elements, but they are not prepared for heavy work. 

Pipe wrench

Pipe wrenches, as their name indicates, have a tubular shape, where the ends are two internal hexagonal sockets. In this sense, they are used as a complement, since they must be activated by a rod. This is a good option for tightening screws that need a certain level of torque and are in intricate places.

Allen wrench

This hex key is strong, efficient and light. It is generally used to tighten set screws. In addition, in some cases it has a T-shaped handle to offer an ergonomic grip. It is worth mentioning that it is called an Allen key due to the success of the American company that has the same name, however, in Germany it is known as Inbus, which refers to the patented system in that country, while in Italy it is called brugola, in honor of the inventor Egidio Brugola.

The main adjustable wrenches


Among the most useful tools is the wrench, hence its great popularity throughout the world. Its main advantage is that it incorporates an adjustable element in the mouth, which with the help of a worm screw, allows the opening to be adjusted according to the shape and size of the nut, for this reason, it is capable of replacing a complete set of keys. fixed. This type of wrench is very useful in cases where a delicate tightening is required so as not to damage the material of the element that we are adjusting.

Stillson wrench

A stilson wrench is a very useful tool on large jobs. It bears the name of the American inventor Daniel Chapman Stillson and works similarly to a wrench, but instead of a screw it has a rack and a threaded ring that join the fixed part with the mobile part. The Stillson wrench is also known as a faucet wrench, since its mouth has a large opening capacity, which is why it is widely used for plumbing.

torque wrench

The torque wrench is one of the most practical and efficient socket wrenches. Although it is similar to the ratchet wrench, its difference is that it allows you to control the tightening torque, since it has an internal mechanism that prevents excessive tightening, thus protecting the screw material. In this sense, it is only necessary to select the tightening torque on the torque wrench to carry out the work with greater confidence.

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