Thousands of nuts and bolts go into manufacturing equipment. Each one of these fasteners requires a tool to turn and, in many cases, that tool is a hand-operated socket. This article aims to provide a comprehensive review of the most common tool in any toolbox: the hand-operated socket, or the socket wrench. We will look to understand how different features of a socket, and its manufacturing process, can make the difference between a high-quality and low-quality socket. Finally, we will also explore how to maintain a socket collection for many decades of intensive use.

Anatomy of a Socket

All sockets might look similar to the untrained eye. Yet, if you had an opportunity to talk to a professional, you probably discovered a strong preference for a particular socket design, or brand.

Sockets are some of the simplest tools ever invented. There are no moving parts, joints, and friction between different components. A socket is a metal “cylinder,” with one side grasping the fastener, and the other side that fits into the ratchet, which allows the operator to apply force and engage the fastener being worked on.

Given the wide range of options available, it is important to understand the main parts of a socket wrench. First is the socket opening, which is the area of the socket that makes contact with the fastener. Each socket will have its opening specified in the description, thus representing the first criteria for choosing a socket.

What is better: a 6-point or 12-point socket?

The most commonly used socket openings are 6-point and 12-point. The 6-point opening is a hexagon with 6 points (vertices) and 6 edges at 60-degree angles. 6-point sockets are also called “single hex” sockets. The advantage of 6-point sockets is they provide a tight fit on 6-point fasteners, making the socket less likely to slip or round-off the fastener’s corners. This is particularly important when working on stubborn fasteners that require a lot of force to remove.

12-point sockets are also called “double hex” sockets. Double hex sockets are easier to connect to fasteners, which can come in handy when accessing fasteners that are hidden or very difficult to see. Additionally, these sockets can be the right choice when working in tight spaces to access fasteners at more angles.

In conclusion, the better socket depends on your application: 6-point sockets should be used on 6-point fasteners that are accessible, especially when good amount of force is required.

Double hex sockets are versatile especially in tight locations, where access to fasteners is limited. Professionals will usually carry both styles to tackle any situation. The socket end drive is located at the opposite side of the opening, where the socket makes contact with the ratchet, extension or other accessories. The most popular drive sizes are 1/4”, 3/8”, 1/2” and 3/4”. However, industrial grade brands such as Gray Tools carry sockets as big as 2 ½” drive size.

The drive end usually features a beveled “dish” that guides the ratchet into the socket or extension. In addition, four dented grooves provide a secure connection with the retaining ball of the socket or extension.

While sockets are available in imperial and metric sizes, to accommodate various types of fasteners, the drive size is always expressed in imperial units, as it is an international standard.

It is very important to ensure the drive end provides a secure connection between the socket and ratchet or extension. A socket that is not properly secured into the ratchet can cause a minor inconvenience (if the socket drops to the ground), or major security concerns and delays (when it drops inside an engine).

Next, the socket wall greatly contributes to the socket’s overall strength and displays important information such as its size and part number. Some sockets feature a knurl that allows for easier removal of the socket from the connecting accessory, even with greasy hands.

Wall thicknesses differ slightly depending on the manufacturer and/or the application the socket is designed for. Regular sockets are extremely durable and provide the strength needed in industrial applications, such as heavy-duty machinery. Thin-walled sockets are very popular in the automotive industry, where access in tight spaces is critical. A thin-walled socket will be lighter and provide less strength than a regular socket, but can be used in a narrower, deeper spaces.

Socket Finish

Hand-operated sockets are generally available in three finishes: chrome, satin, and black oxide:

1) Chrome-plating is the most popular finish in North America, and for good reason. Chrome sockets are easy to clean and resistant to corrosion. A word of caution: never use a socket if you notice the chrome finish flakes off, as chrome can be as sharp as a blade and can cause serious injury. Most brands offer a lifetime warranty on their sockets and will be able to replace your affected sockets.

2) Satin finish is very popular outside of North America. This finish can provide a slightly better grip and make some imperfections less visible. In some cases, satin finish sockets might be less expensive than the chrome equivalent.

3) Black-oxide finish, almost exclusively belonging to impact sockets, is used to finish hand operated sockets, although it is not nearly as popular as the chrome or satin finish. For this reason, black oxide hand sockets can be easily confused with impact sockets. It is important to do your research and understand the functionality of the sockets you are buying.

Black oxide sockets are easy to clean and usually less expensive than chrome sockets. The size markings, especially if laser-etched, are more visible on the black surface than on mirror chrome. On the downside, black oxide sockets are more difficult to find in low light environments.

Socket Material

The vast majority of hand sockets are made of alloyed steel, meaning that a small percentage of other materials have been added to provide the sockets with the required hardness, strength and ductility.

The two most common socket materials are chromium-molybdenum (CRMO) and chromium-vanadium (CRV). The markings on the sockets with either symbol can generate passionate discussions as to which material is superior. One perception is that sockets imported from Asia are made of CRV, since most of these sockets have the CRV symbol stamped on the sockets, while domestic manufacturers use CRMO.

In reality, both materials produce high quality sockets, as the chemical composition of these materials are very similar. The manufacturing process and quality control will make the difference in quality, as we will see below.

Socket Manufacturing

Although simple in design and functionality, a socket goes through a lengthy and precise manufacturing process before it can be safely used to turn a fastener. The most important steps of making a socket are presented below, while each socket manufacturer might employ additional processes for their particular range.

Cutting the steel bars to desired lengths: The socket manufacturing process starts with a bar of steel that is fed through a die and cut to the desired lengths. Small cylindrical sections are created which will eventually become the shiny sockets we’re familiar with.

Forming of hexagonal shapes: The cylindrical parts created in step 1 are sent through a series of forging machines, in a process is called cold forming. Shaping metal at near room temperatures improves its tensile strength while still allowing high levels of manipulation.

Cleaning and machining: Sockets are tumbled through a washer/dryer system to remove lingering lubricating oil. Computerized machines then remove sharp edges and cuts a bevel on the socket’s inner rim so it will slide on to bolts more easily.

Stamping: A series of rolling stamps engrave important information on the socket wall, such as the company name, part number and size, and sometimes the type of steel used to manufacture the socket.

Heat treating: Heat treatment, in the case of a socket, is used to increase the hardness of the base material. Raw carbon steel that has not been heat treated is relatively soft and would deform when used to perform work. This would result in premature wear, breakage, deformation and failure.

Any metal part used to perform work or one that must contact another metal part must be heat treated to avoid wear and failure. By heating a metal to a high temperature and holding it there, its physical properties will change and the material will become harder when cooled. Cooling the material sets the properties at the hardness desired.

Heat treatment is governed by the required hardness and material specification. Each type of steel has to be heat treated in a specific manner with a specific temperature required to achieve the desired hardness. The manufacturer specifies the required hardness and the type of material and then the appropriate heat treatment process is used to achieve the desired result. Time in the furnace depends on the required hardness and the material used.

Time is only important in that the hardness to be achieved requires a specific time at the higher temperature (think of it like baking a cake – baking it longer will not result in a better cake, it is more about the quality of the ingredients, the recipe and the oven itself). Each material and hardness has its own recipe. The quality is dependent on the heat treatment reaching the desired hardness and is influenced more by equipment and process.

The rapid cooldown hardens the metal. This is called “quenching,” and it is achieved by submerging the lot of sockets in a cooling medium, such as oil. The quenching process is tightly controlled, with the heating temperature, cooling method, cooling medium and cooling speed all dependent upon the type of material being quenched and the desired hardness. In general, the cooling is quite fast when compared to the heating, as the desired result is to set the hardness as quickly as possible.

Shot blasting: Some manufacturers send the sockets into a chamber where they are blasted with fine steel particles to remove imperfections and polish them. A lot of products will be put into a chamber with a rotating belt and, as the belt rotates, steel shot is blasted at the parts to smooth them and remove any debris. This takes on average 10 to 15 minutes per lot.

Rotobarrel: Sockets go into a tub of fine ceramic stones and mild acid to create a smooth finish on which chrome will adhere to. The rotobarrel process usually takes around six hours per lot. The specific chemical recipe and the quality and type of media is what determines the quality of the finish and, for the most part, this step is used as a sort of polish to take all inconsistencies, any remaining dirt, burrs and rough spots off the surface of the product. It results in a shinier product and a cleaner surface to receive plating.

The time and delivery of the chemical in the rotobarrel is precisely controlled based on the amount of material being tumbled and burnished. Leaving a product too long in the rotobarrel can be detrimental to the finish, as the acid can etch the surface. Not running it long enough will result in a duller finish.

Washing and rinses: The purpose of this process is to prepare sockets for chrome plating. This is part of the electroplating process, which is necessary before chrome plating.

Chrome plating: Some manufacturers like Gray Tools use a nickel chrome plating process. The nickel is deposited first and is the main protection for the product. The nickel adds an element of protection to the socket and guards against wear as well as corrosion and rusting. It also creates a better surface to which the chrome will adhere. The chrome is then deposited over the nickel to provide an added layer of protection and a cosmetically pleasing “shiny” finish.

Each step in the plating process is precisely timed, and there may be many steps including cleaning, the addition of nickel, further cleaning, addition of chrome, rustproofing, etc., depending on the product. If the surface is not properly prepared before the deposition of the nickel and chrome layers, the end result will be either an unacceptable chrome finish (yellow or dull milky appearance etc.) or poor adhesion. The chrome and nickel layers are only a few microns thick.

Immersion into a rust proofing solution: This step is also part of the electroplating process and ensures the socket will be protected from rust when used in various work environments.

Spinning to remove excess rust: This is part of the drying process done in electroplating and is done in different ways by different manufacturers.

What Makes a High-Quality Socket?

A high-quality socket will last for many decades. Here is a checklist of things to look for when adding to your socket collection:

• Inside forging: Is it smooth and level?
• Wall thickness: Does the socket feel solid in your hands?
• Exterior finish: Do you notice any imperfections in the finish, such as chrome peeling, or signs of rust?
• Interior finish: High-quality sockets have the interior coated with a rust prevention material.
• Socket markings: Do the markings look durable? If the markings wear off easily, you won’t be able to identify the socket size and part number (useful for warranty claims).
• Does the socket opening feature radiused corners to prevent fastener round-off?
• Does the socket connect securely with a ratchet and extension?
• Socket brand: Is the socket made/offered by a reputable manufacturer known to stand behind the products?

How to Properly Use and Maintain Your Sockets

• Always use the exact size socket to operate the fastener. Failure to do so can damage the fastener and lead to personal injury.
• Do not use metric sockets on imperial bolts and vice-versa, as the chances of socket slippage increase dramatically, resulting in fastener damage and personal injury.
• Do not use your hand sockets with an impact gun, as the force generated will permanently damage the socket.
• Do not alter your sockets by welding attachments to improve leverage.
• Do not store your sockets in a moist environment.
• Clean your sockets regularly.

About the Author: Paul Dean is the VP of Operations at Gray Tools. He has over 30 years of manufacturing and operations experience, helping thousands of professionals build and maintain their tool collections for years of reliable use.