What is a Socket Screw?

Socket Screws

Socket screws are a kind of screw designed and manufactured using an internal hexagonal (hexagonal) drive built into the head. As such, they are designed to be tightened and loosened with an Allen wrench or hex key, as opposed to a standard screwdriver. This is the key feature which sets a socket screw apart from other screw head drive styles like the Phillips head screw, slotted, flathead screws, and Pozidriv screws to name just a few.

Another common distinction is that socket screws are usually squared off at the tip. These are normally referred to as flat point socket screws and they tend to be the most widely used kind found in many common applications. Although, it is worth noting that several other designs are also available.

In most other regards, there is not generally much physical difference between socket screws and standard screws for the majority of everyday uses. So what exactly is the point of a socket screw, and when should you use it?

Basically, socket screws join some of the increased performance features of other common hex fasteners nut and bolt systems being the apparent point of reference with the convenience and ease of use of a regular format screw set. This middle ground could be a useful compromise in many situations, especially when working in small spaces or areas without easy access to secure externally wrenched hex fasteners.

Socket Screw

Advantages of Socket Screws

 

The potentially higher torque and clamping force that can be obtained with a hexagon socket screw over an ordinary screw make it a preferable option in some applications. Compared to standard screws and bolts on a model for a similar test, socket head screws can typically provide some or all of the following benefits in relevant scenarios.

Since socket screws generally provide higher clamping force than regular screws and many other small-format fastener types, fewer socket screws could be used in a given application to obtain the same all-around clamping force on the joint or workpiece. Using fewer screws means:

 

• Lowered hardware costs
• Fewer holes to drill and tap into mounting surfaces, saving time and lowering potential damage to components
• Lower the total weight of the finished product

 

The trend towards lightweight constructions while using socket screws is further improved because of their smaller individual size than many other kinds of screws And the fastening components, particularly with respect to the fastening arrangements of nuts and bolts.

In particular, the cylindrical heads and internal drives of hexagonal socket head screws have a much smaller diameter than the external hexagonal head fasteners and thus require less space without extra space required to manoeuvre a wrench for installation.

Hex Socket Screw

What is a Socket Head Cap Screw?

 

The name 'cap screw' was generally used as an umbrella term, meaning any one of the several screw types selected for fastening applications where the use of a nut and bolt installation was considered inappropriate. Although, today, it tends to refer specifically to a certain style of screw head.

Any number of different screw types and shapes could incorporate elements of the basic cap screw head design you may find anything from shoulder screws and countersink screws, through to button and fillister head screws are generally described as cap screws. A socket head screw is also commonly known as a socket screw, an allen bolt or simply a socket screw. In many ways, it is very much the regular version of a socket screw.

Socket head cap screws are used extensively in industrial production as well as assembly lines, including in the automotive sector, furniture manufacture, machine tooling applications and steel fabrication. This is chiefly because of the fact that they are simple to install and tighten or loosen, as well as offering impressive clamping strengths while maintaining a discreet and tidy finished look.

As with the vast majority of all socket screws, the socket head cap screw features a cylindrical head with an internal hex drive hole and is usually threaded all the way along the full length of the shank. Similarly, they are mainly designed to be used in assemblies where there is not sufficient clearance to install a traditional nut and bolt or to manoeuvre a regular socket wrench.

Socket Head Cap Screw

Socket Screw Sizes

 

The ordinary socket cap screw head is around 1.5 times the diameter of the screw shank, and about as high as the shank is wide. Although, replacement head designs for socket head cap screws consist of low head, button head and flat head varieties, designed for driving into countersunk holes and other application-specific mounting positions.

When looking to buy socket screws, note that the stated length of the product is generally measured from immediately under the head to the tip. This is the case for most screw types, but some certain varieties - thumb screws, for instance will usually give stated length measurements which include the height of the head in the overall specification.

Most socket screw types are available in either metric or imperial measurements for length and diameter, depending upon the certain manufacturer or supplier in question. Many large brands and socket screw manufacturers will generally offer a socket screw sizing chart or similar tool which could be referred to at the point of sale.

While relatively small socket screw sizes of diameters starting from M2 to M6, and lengths of around 3 millimetre to 20 millimetre tend to be in greater demand across an extensive range of tasks and applications, the complete range of available sizes is considerable. Larger, heavier gauge and extra-long socket screws are not at all unusual, especially in widths of around M8 to M20, and lengths of anywhere up to 130mm.

Extra-long socket screws are generally found in electrical plug sockets. Regular electrical socket screw sizes include 40mm, 50mm, 60mm, 75mm and 100mm.

Hexagon Socket Head Cap Screw

 

Socket Screw Materials

 

There are many different materials used in the production of socket screws. The most common materials are steel and stainless steel but options include brass, aluminium, black nickel, zinc-plated and chrome socket screws. The ideal material to choose will depend on the precise application where the socket screw will be used.

Some of the most common socket screw materials are:

 

Aluminium Socket Screws

 

Aluminium socket cap screws are generally preferred for applications in which weight is a key factor. This may include applications starting from the automotive industry through to uses like installing hardware and trim on moveable furniture, cabinets, doors and windows.

While aluminium weighs only about one-third of the weight of the steel, it is durable and tends to have a lower shear strength. While aluminium provides decent performance in terms of corrosion resistance in more challenging environments, it is less hardwearing than stainless steel.

Aluminium Socket Screw

 

Zinc or Nickel Plated Steel Socket Screws

 

The main reason why so many sets of steel socket cap screw are available with zinc or nickel plating alternatives is for the superior corrosion or rust resistance this easy manufacturing process could provide screws of all types.

Combined zinc-nickel plating is usually considered to be a tougher coating up to twice the hardness when compared to regular zinc plating, and it could also deliver up to four times the corrosion resistance of other metallic coating methods. While, it is generally more expensive, and might not be considered a cost-effective option in many applications where ordinary galvanized steel socket screws would suffice.

Zinc Plated Steel Socket Screw

 

Nickel Plated Steel Socket Screw

Brass Socket Screws

 

Brass socket cap screws may be usually preferred for their aesthetic value, but as an alloy of copper and zinc, brass or brass-tipped socket screws might provide further advantages in specific situations. Brass is stronger than copper alone, however it will still be considerably less rigid than most varieties of steel or stainless steel socket screw.

Although, it is also worth noting that brass plating will be less resistant to corrosion than solid brass socket screws. If the product will be used in an exposed location or outdoor application, solid brass socket screws are the preferable alternative.

Brass Socket Screw

 

Types of Socket Screws

 

In addition to the different materials, socket screws are also available in different types:

 

Button Head Socket Screws

 

Button head socket cap screws are also called as round head or dome head socket screws. They are fabricated with a smooth, slightly rounded dome at the head, which tends to be somewhat larger and more bulbous than regular cap screw varieties.

Usually, this means that a button head socket screw could be big enough for a larger gauge of hex key or driver, and thus could be affixed with more torque to obtain greater clamping forces. Although, smaller sized hex socket button screws should be fastened with less torque. Button socket screws could also be supplied with tamper-proof drives.

Button Head Socket Screw

Countersunk Socket Screws

 

Hex socket countersunk screws, are otherwise called as flat or flat head socket screws, and they are used in applications where it is essential that the installed screw sits flush with or just underneath the surface of the workpiece.

Countersunk socket screws feature a sloping shoulder design generally at a normal angle of around 82 degrees which permits the screw to bed down into the surface via a pre-drilled countersunk hole. Again, they are available in various lengths and widths and are extensively available under both imperial and metric socket screw sizing charts.

Countersunk Socket Screw

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