Ultimate Guide to Captive Screws: Types & Applications

1. A Guide to Captive Screws

Captive screws are important pieces of hardware that can be used in household, commercial, and industrial applications. Unlike conventional screws, captive screws do not automatically release from their housing when unscrewed. 

Captive screws were invented to meet a common challenge faced by engineers: lost screws. When unscrewing conventional screws to remove a panel cover on a piece of heavy machinery, for example, it is easy to drop or misplace screws that are not attached to the panel. These dropped screws can even fall into operating machinery with disastrous results.

Captive screws can be unscrewed from their matching part in the machine body to allow removal of the panel, but they are ‘captive’ to the panel itself. This prevents loss and allows the panel to be safely and easily replaced when the internal maintenance is complete. Captive screws are particularly useful for affixing panels that will be frequently removed and reattached.

Because of the safety and convenience advantages offered by captive screws, they have become the standard for many commercial and industrial uses and are even required to meet some industrial safety standards.

In this article, we will explore how captive screws work, how to attach them, and their various types and construction materials. Whatever use case you are considering, there is a captive screw that will meet your needs.

1-1. What is a Captive Screw?

Captive screws are easier, safer, and more foolproof to use. That is why they have become the standard for industrial-grade equipment. An archetypal captive screw assembly consists of a few main components, which we explain below:

• The Matching Part: The main body to which the panel and captive screw are affixed. The matching part contains the threaded slot that receives the screw body.

• Panel: The panel is the hardware being affixed to the matching part such as housing using the captive screw. The screw body is ‘captive’ to the panel, i.e. it does not separate from the panel even when unscrewed from the matching part (housing).

• Screw Body: Instead of the screw directly attaching to the panel, it is the ferrule that serves as the connection point. The screw body, together with the ferrule, is used to securely fasten the panel to the matching part. 

• Retaining Washer or Flange: Optionally, the screw body may be held in place by a retaining washer or flange, which is a piece of hardware on the opposite side of the panel from the head of the screw that prevents the screw from slipping out of the hole when unscrewed from the matching part. We will explore other assembly types in more detail later on in the article.

Manufacturers have developed many different captive screw designs using different materials and with different advantages. Check out our robust catalog of captive screw options with user-friendly plastic heads that enable tool-free access in a variety of attractive colors.

2. How to: Captive Screw Assembly

One of the main differentiators among the various models of captive screws is the assembly design. This refers to the way the ferrule of the screw body is installed and held ‘captive’ to the panel. Ease of installation and sturdiness of the connection are the two main factors that separate the various assembly types. Depending on your use case, one assembly type may be more suitable than others.

The main assembly types are: press-in, flare-in, floating, and surface mount technology (SMT). We will explore each in greater detail below so that you can understand what assembly type fits your use case.

2-1. Press-in Captive Screws

Press-in captive screws represent a relatively new assembly type that balances ease of installation with sturdiness. A press-in captive screw uses a ferrule that is forcibly inserted through a hole in the panel that is smaller than the topmost section of the ferrule. The force will displace the section of the panel immediately beside the ferrule, and the panel will cold flow into an undercut beneath the lip of the ferrule. This creates a tight fit between ferrule and panel. Then the whole panel assembly is ready to be screwed into the matching part(housing).

Press-in captive screws can be a good choice for consumer electronics like laptops and smartphones, commercial electronics like data centers, industrial machines, and medical devices. Their main advantage is their mix of ease and sturdiness. Press-in screws offer a reliable solution for bonding panels of varying thicknesses, effectively overcoming the limitations of flare-in techniques that struggle with thicker panels.

This method also eliminates the potential drawbacks associated with soldering, such as the risk of thermal damage and weld splatter that can harm nearby components. It is worth noting, however, that press-in captive screws may not be suitable for use on printed circuit boards and may not achieve a completely seamless finish. In addition to these considerations, welding can pose further challenges, including the potential damage to the electroplating layer, leading to rust, as well as the unsightly blackening and aesthetic degradation of the ferrule.. Press-in captive screws are not suitable for use on printed circuit boards and may not result in a perfectly flush finish.

2-2. Flare-in Captive Screw Installation

Flare-in captive screws are installed by creating a flared lip on the screw assembly that prevents the screw from separating from the panel. The fastener is inserted through a hole in the sheet, then a machine press is used to flare the lip of the ferrule until it is wider than the hole through which it entered and flush with the panel surface. This flaring prevents the ferrule from exiting back through the panel. 

Flare-in captive screws are well suited for applications on soft metals, hard metals, and printed circuit boards because of the relatively little force that is used to attach them. Most of the force used to install a flare-in captive screw is actually directed at the ferrule and not at the panel sheet, making it ideal for delicate applications. It is also relatively good at achieving a finish flush with the surface of the panel. They are an especially common choice for applications that need aesthetic polish, such as when the panel is painted metal.

Using a flare-in captive screw can prevent damage to the finish that might occur using a press-in captive screw assembly. Unlike press-in captive screws, flare-in screws offer the advantage of being less restrictive in terms of panel material. They can even be used with materials like plastic. This versatility expands their range of applications. Additionally, using a flare-in captive screw assembly helps safeguard the finish, preventing potential damage that could occur with a press-in method.

2-3. Floating Captive Screw Installation

Floating captive screws are affixed to the panel using a fastening washer and press. The screw ferrule is inserted through the hole in the panel, fitted with a washer, then plugged with the washer to create a secure connection. Pressing the ferrule causes it to deform and grip the washer, firmly attaching it to the panel. Unlike how flare-in and press-in screws attach to panels, floating captive screws connect with the washer and allow more space in between. This design feature enables greater freedom of movement in both directions, enhancing the overall flexibility of the screw assembly.  You can watch the process on Fivetech’s YouTube channel.

These captive screws are suitable for use with aluminum, carbon steel, and printed circuit boards, which allows greater flexibility. Floating captive screws are also top performers when it comes to ensuring a fully flush edge with the panel.

2-4. SMT Captive Screw Installation

Surface mount technology (SMT) captive screws are designed for printed circuit board (PCB) applications. They are a soldered captive screw design, which are affixed to the panel with melted solder paste and installed using a vacuum absorber. The melted solder paste bonds the screw assembly to the panel. This installation technique enables fully automated installation as part of the PCB manufacturing process.

Fivetech’s SMT captive screws are also built for tool-free use with simple plastic-sided hand screws. This makes for easier operation and reduces risk of damage from use of heavier tooling around delicate circuit boards. Because SMT captive screws can be directly installed as part of the circuit board manufacturing process, they may make sense for application in mass production of manufacturing industries in various sectors of mechanical engineering.

3. The Types of Captive Screw Designs

Now that you understand the functional mechanisms that enable captive screws, the next step is understanding the screw’s operation type, material, and sizing. There is not a standard way of designing or sizing captive screws, which means products produced by different manufacturers may be incompatible. This also means there are many different varieties of captive screws on the market, which may make it likelier that there is a model already for sale that meets your exact need.

Captive screws can be produced in both metric and imperial screw sizes and can have different screw heads (flat, Phillips, hexagonal, etc.). It is important to fully understand the requirements imposed by your proposed application before deciding the appropriate captive screw option for you.

3-1. Captive Panel Screw

Captive panel screws, also sometimes called captive fasteners, are a popular choice for applications like 5G telecommunications devices, computer servers, and medical equipment. This screw type is available off-the-shelf primarily in press-in assembly types, but there are also some flare-in options.

One of the distinguishing features of Fivetech’s captive panel screws is that the screw is spring-loaded into the ferrule. This means that when in an unlocked position, the screw is automatically retracted from the matching part, keeping the panel open. When the screw is tightened, the spring is compressed as the screw body is secured in the matching part. This makes Fivetech captive panel screws especially easy to operate.

The screws are constructed of hardened carbon steel finished with nickel or zinc for maximum longevity. The spring components are stainless steel, and the fastener ferrule may be either fully hardened carbon steel or a combination of carbon steel and aluminum. Some captive panel screws also include plastic grips on the screw head to enable easier fastening and unfastening by hand. The plastic component may be color-customized. Beyond simplifying the color-coding of various maintenance activities for your product, this feature also allows you to tailor the colors to align with your corporate identity. 

3-2. Captive Thumb Screw

Captive thumb screws are specifically optimized for tool-free use. This makes them an easy choice, especially for tight spaces that may preclude the easy use of a tool. Thumb screws generally have plastic grips attached to the screw head to enable comfortable fastening and unfastening by hand. This plastic grip serves more than one purpose. Not only does it increase comfort and grip, but it also dissipates electric charge and limits heat conductivity from potentially hot metal components. The plastic piece can be customized with a range of vibrant colors.

The metal screw body for thumb screws is typically stainless steel or low carbon steel, which makes them durable and long-lasting options. Some thumb screws may also have aluminum components ensuring they stay lightweight and easy to use.

Take a look at our Fivetech’s full catalog of thumb screws. There will certainly be an option that can be customized to your use case.

3-2-1. Plastic Captive Screws 

Plastic captive screws are an increasingly popular choice for many use cases across 5G telecommunications, data center equipment, medical equipment, and other product categories. Plastic refers not to the screw itself but to the outer casing applied to the screw head. It provides the benefits of metal construction: a sturdy and durable screw connection with the fastener, panel, and housing. And, it also brings additional benefits:

• Easier to operate: Plastic-coated captive screw heads can be easily operated by hand without the use of a tool.

• Safe to use in hot environments: Captive screws will be required to work inside heat-generating industrial equipment. The plastic grip on the head of Fivetech captive screws allows easy hand operation without the risk of burns.

• Reduces electric charge: All-metal equipment can carry an electric charge and result in a shock when you get near it. Plastic captive screws prevent this because the plastic coating acts as an insulator that disrupts the charge and allows safe and comfortable operation.

Plastic captive screws also come in a variety depending on the height of the screw lock after it is attached to the panel. Depending on height, they range from regular, low-profile, or high-profile designs. This refers to the amount that the head sticks up from the screw assembly. A low-profile screw may be ideal for use cases where space is tight, but a high-profile head may increase accessibility and ease of maintenance when space is not an issue. We will explore low-profile plastic captive screws in greater detail below.

Each plastic captive screw head design can be manufactured in any assembly type, be it press-in, flare-in, floating, or SMT. In addition, a trusted manufacturing partner like Fivetech can customize many aspects of captive screws, including their head specifications, to meet your exact application.

To look for a plastic captive screw to meet your needs, check out Fivetech’s catalog of popular products.

3-2-2. Low Profile Captive Screws

Low-profile captive screws provide a mix of advantages that may make them ideal for your use case. They are characterized by a screw head that protrudes less noticeably. For tool-free captive screws, this shorter profile may actually make them slightly more difficult to use. However, they are an excellent solution for applications where space is at a premium and the screw head must stay closer to the panel to avoid interfering with other equipment components.

They are different from flush captive screws because they still do stick up above the surface of the panel. This means they have a mix of usability found in regular and high-profile captive screws and compactness found in flush captive screws.

As with other plastic captive screws, Fivetech’s low-profile captive screws are available in a number of screw head types, finishes, plastic colors, and assembly designs.

3-2-3. Metal Captive Screws

Metal captive screws can also be a great option. They are the most traditional form of captive screw. They are constructed from a variety of metal types including stainless steel, carbon steel, steel alloys, and aluminum and may also be finished in metals like zinc or nickel.

Metal screws can showcase a metallic sheen, and if color identification is necessary, they can undergo a painting process to achieve the desired appearance. However, it is important to note that metal screws carry a higher risk of paint chipping compared to plastic screws.

Some metal captive screws even have innovative security sleeves that prevent them from being turned using a wrench or by hand. This can ensure that a panel containing sensitive equipment is only opened by an appropriately trained technician using the prescribed screw head.

Here, you can find a number of excellent metal captive screw options we offer.

4. Explore a Wide Range of Captive Screws Options at Fivetech

In conclusion, captive screws are essential hardware components that provide safety and convenience in various applications. Their ability to remain attached to panels, even when unscrewed, prevents the loss of screws and potential hazards in industrial machinery. Captive screws have become the standard choice for many commercial and industrial uses and are often required to meet safety standards.

This article has explored the working principle of captive screws, their attachment methods, and different types and materials available. Whether you need captive screws for household, commercial, or industrial purposes, there is a suitable option to meet your needs.

To explore a wide range of captive screw options, including user-friendly plastic heads in attractive colors, visit our homepage for more information. Make the smart choice and ensure the safety and convenience of your applications with high-quality captive screws.