Automotion Components is a leading manufacturer of captive screws (also known as captive nut fasteners) and captive thumb screws. Also available to purchase online are threaded washers and retaining flanges for captive screw installation on thin or non-threaded panels. We manufacture our captive screws in many materials (and finishing options) including stainless steel (e.g. for medical applications), titanium (for aerospace etc.), and many others!
Read more about Automotion Components offering and use of captive screws.
Captive screws are designed to provide “captivation” (meaning a permanent hold). They can be removed from their installation, but only intentionally, and are very unlikely to fall out accidentally once installed, as the smooth shoulder of the captive screw remains in the panel unless specifically unscrewed.
Screw captivation is important because in the past, screws were going missing during machine maintenance, leading to panels being improperly reattached after servicing, eventually resulting in workplace injuries when people accidentally put their hands inside machinery. For this reason, permanent fastenings (such as captive screws) are now legally required on certain equipment, such as safety covers/panels, to comply with EU law (2006/42/EC; Machine Safety Directive) and/or ISO 14583. The use of captive screws minimises the chances of a screw being lost during servicing or maintenance because usually, the captive screw remains with an assembly - e.g. a guard panel that can be lifted off another part.
Captive screws are ideal for applications that require secure, permanent installations (for instance, safety panels on industrial machinery in which a loose or lost screw could cause damage). They do not fall out of the safety panel unless specifically unscrewed via the threaded hole.
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Captive screws are designed to provide “captivation” (meaning a permanent hold). They can be removed from their installation, but only intentionally, and are very unlikely to fall out accidentally once installed, as the smooth shoulder of the captive screw remains in the panel unless specifically unscrewed.
Screw captivation is important because in the past, screws were going missing during machine maintenance, leading to panels being improperly reattached after servicing, eventually resulting in workplace injuries when people accidentally put their hands inside machinery. For this reason, permanent fastenings (such as captive screws) are now legally required on certain equipment, such as safety covers/panels, to comply with EU law (2006/42/EC; Machine Safety Directive) and/or ISO 14583. The use of captive screws minimises the chances of a screw being lost during servicing or maintenance because usually, the captive screw remains with an assembly - e.g. a guard panel that can be lifted off another part.
Captive screws are ideal for applications that require secure, permanent installations (for instance, safety panels on industrial machinery in which a loose or lost screw could cause damage). They do not fall out of the safety panel unless specifically unscrewed via the threaded hole.
Captive Screw Options
Our captive screws are available in stainless steel (AISI 303 (A2) and 316 (A4) series), titanium, aluminium and more. Metric and imperial dimensions. See our technical information page to read more about the materials and finishes we can produce.
Stainless steel (AISI 303 & 316) with thread sizes between M 2.5 - M 20 and lengths ranging between 5 - 80mm. Example shown is an Anu-Lok 180 locking patch. Alternative materials, finshes and head types available.
Zink plated steel captive screws, ranging from M 2.5 - M 20, length between 5 - 120mm and with hex drive. Also available on request in anodised or black oxide steel.
Black oxide coated with thread sizes betmeen M 2 - M 20 and lengths ranging from 5 - 120mm. The black oxide also provides another form of defence against corrosive environments.
Titanium screws with thread sizes between M 2.5 - M 12 and lengths 8 - 120mm. They are even more lightweight and corrosion resistant than our stainless captive screws, but more costly due to the material. Excellent for aerospace and marine applications.
Can be hand-tightened and are available in stainless AISI 303 or 316, blackened stainless, titanium, aluminium and brass; ranging from M 3 - M 8 and 10 - 60mm long.
Associated products
Retaining Flanges & Captive Washers
What is a retaining flange?
Retaining flanges are useful for affixing thin, non-threaded panels with captive screw fastenings. When installed on a thin panel, the retaining flange provides a threaded hole for the captive screw.
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Ideal for the installation of captive screws on thin or unthreaded sheet metal panels.
To be used with captive screws for added security. They can be used on panels with any thicknes, as long as the unthreaded portion of the captive screw is longer than the panel width plus the washer thickness.
M 2 - M 20.
Associated products
Retaining Flanges & Captive Washers
What is a retaining flange?
Retaining flanges are useful for affixing thin, non-threaded panels with captive screw fastenings. When installed on a thin panel, the retaining flange provides a threaded hole for the captive screw.
Ideal for the installation of captive screws on thin or unthreaded sheet metal panels.
To be used with captive screws for added security. They can be used on panels with any thicknes, as long as the unthreaded portion of the captive screw is longer than the panel width plus the washer thickness.
M 2 - M 20.
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Head Types
| Schematic | Drive Types | Uses |
 | Hexagonal recess | Ideal for precision assembly. Most recommended where less surface area is available. |
 | Crosshead (Phillips®) | Provides good drive control. Always use a driver bit of the proper size which is in good condition. |
 | Star Head (Torx®) | Positive-engaging, fast-locating method which transmits drive torque with less required downward pressure. Good fastening appearance. |
 | Slotted | Accepts standard blade screwdriver. Requires less downward pressure to drive parts than those with recessed openings. Use a proper fitting blade to minimise slippage. |
 | Security | These screws are impossible to remove without the special matching screwdriver. |
How do Captive Screws work?
Generally, captive screws have a smooth (non-threaded) shoulder/shank that has a smaller diameter than the threaded end portion. The captive screw is placed through the first panel and then on to the frame (e.g. machinery housing). The captive screw is placed through the first panel either: via a threaded hole in the panel, or - if the panel is non-threaded - via a threaded washer or retaining flange.
When you unscrew a panel that is fastened to a frame by a captive screw, whilst the panel is lifted off the frame, the smooth shoulder of the captive screw remains within the panel. Captive screws cannot be released from the panel unless specifically unscrewed by means of the panel’s threaded hole (or other threaded washer/flange). This is advantageous because the captive screw remains in the panel, so the risk of losing a component is minimised, and the panel can be re-mounted easily and quickly. In addition, if the equipment is subject to vibration or other disturbances, even though the screw could come loose, it will not fall out and cause damage to a production line, for example.
Examples of captive screw installations
Captive screws installed on a threaded panel will not fall out, even when loosened.
Captive screws on a threaded panel attached to machinery housing.
Captive screws can be retained on non-threaded panels by using threaded washers.
Captive screws installed on a non-threaded panel via threaded washers.
How to choose a Captive Screw for your application
The captive screw should be selected based on its length and thread size.
Most importantly, 'x', the space between the two threaded areas in the application should be greater than the thread length (l2) of the captive screw. This will ensure that when the captive screw is loosened from the frame, it will not interact with any threading on the panel.
The threading (d1) on the panel and the frame (or housing) must be the same so that the captive screw interacts appropriately with both fixtures. For non-hollow panels/housings, d4 must be greater than d1.
The panel does not have to be threaded, and instead, some of our customers prefer to use a non-threaded panel with a threaded captive washer (e.g. P0168 - see bottom right diagram in the application images) or retaining flange (for thin panels; e.g. P0169). To understand more about how retaining flanges for captive screws work, see our video above.
How to choose a Captive Screw for your application
The captive screw should be selected based on its length and thread size.
Most importantly, 'x', the space between the two threaded areas in the application should be greater than the thread length (l2) of the captive screw. This will ensure that when the captive screw is loosened from the frame, it will not interact with any threading on the panel.
The threading (d1) on the panel and the frame (or housing) must be the same so that the captive screw interacts appropriately with both fixtures. For non-hollow panels/housings, d4 must be greater than d1.
The panel does not have to be threaded, and instead, some of our customers prefer to use a non-threaded panel with a threaded captive washer (e.g. P0168 - see bottom right diagram in the application images) or retaining flange (for thin panels; e.g. P0169). To understand more about how retaining flanges for captive screws work, see our video above.
Material Options in Focus
| Material | Notes |
| Stainless steel: AISI 303 series (Our code: A2) | 303 series stainless steel (1.4305) is a machinable stainless steel grade with good corrosion resistance properties. For more information, see our stainless steel technical page, written with engineers in mind. |
| Stainless steel: AISI 316 series (Our code: A4) | 316 series stainless steel (1.4401) is an exceptionally corrosion resistant stainless steel grade. It can withstand acidic and marine environments and is more expensive than 303/304 series stainless steel. We can also offer passivation and other coatings to protect the anti-corrosion surface. |
| Titanium: Grade 2 (Our code: T2) | ASTM B348 grade 2 titanium is commercially pure titanium metal and is exceptionally corrosion resistant. Titanium has a high strength:weight ratio and is excellent for offshore or aerospace applications. |
| Titanium: Grade 5 (Our code: T5) | ASTM B348 grade 5 titanium is a titanium alloy (Ti6Al4V). It is stronger than grade 2 titanium and is heat treatable. It has a very high strength:weight ratio and is used in aerospace, power generation, and medical industries (among others). Titanium is more expensive than stainless steel. |
| Steel | Very strong, although prone to corrosion in certain environments. Coatings are available (e.g. zinc plating). We offer various different grades of steel (e.g. 8.8, 10.9), specified in the product material notes. |
| Aluminium (Our code: AL) | Aluminium is a lightweight metal with good oxidation resistance properties. |
| Brass (Our code: BR) | Brass is an alloy of copper and zinc. It is resistant to oxidation and corrosion but is not compatible with amines or ammonia. It usually has a golden/yellow metallic lustre. |
| Monel (Our code: MN) | A single phase nickel-copper alloy with excellent properties at both very high and very low temperatures. It is therefore used in certain areas of aircrafts. It has a high density and is very difficult to machine, so it is approximately 3x more expensive than carbon steel, and also more expensive than stainless steel. |
Finishing Options in Focus
Coatings
Many finishes can be applied - black oxide finish, anodizing etc.
The main options are as follows:
| Finish | Notes |
| Black Chrome (MIL-C-1458B) | Black chrome is a hard, non-reflective coating which is resistant to abrasion, heat and erosion. The black chrome surface is a dull, dark grey and may be waxed or oiled to darken the surface further. |
| Black Oxide Coating (MIL-C-13924B) | Black oxide is a uniform black coating for ferrous metals. Generally it is considered a decorative coating and provides only very limited corrosion protections under mildly corrosive conditions. |
| Cadmium | Cadmium is a bright, silvery white plating. Supplementary treatments for type II can be golden, iridescent, amber, black or olive drab. |
| Passivate (QQ-P-35/MIL S-5OOSC) | Passivation is a process designed to remove foreign metals or impurities which may have been introduced during manufacturing/processing from the surface of stainless and corrosion resistant steels. This helps keep the protective anti-corrosion surface film intact and slows corrosion. |
| Phosphate Coating Light (TT-C-0D490B) | Phosphate coating is a light coating for use as a base paint. |
| Gold (MIL-G-45204B) | Yellow to orange colour depending on a proprietary process used. Will range from matt to bright finish depending on base metal. Good corrosion resistance and high tarnish resistance. |
| Nickel | Nickel is a corrosion protective plating for steel, zinc and zinc alloys as well as copper and copper alloys. |
| Zinc (QQ-Z-325C) | The primary use of chromate finishes on zinc is to retard or prevent formation of white corrosion products on zinc surfaces. |
Why choose Automotion Components' Captive Screws?
We have a large range of captive screws in stock
Our captive screws come in a range of head styles, materials and finishes. Our most popular captive screws are made from stainless steel (AISI 303, 1.4305) or marine-grade stainless steel (AISI 316, 1.4401). The strength class of the stainless steels used to produce our captive screws is class 50. We also have titanium (ASTM B348 grades 2 and 5) captive screws in stock and many more options for bespoke products.
We can produce bespoke captive screws for our customers
We can manufacture any special requirements to customer drawings easily on our fully automated machines (we may require a minimum batch size for this bespoke option). Other material choices include steel, titanium, monel, aluminium etc. Finishing options include a black oxide coating, zinc plating and more. We can also make a variety of special head types. See our captive screws technical information page for more details.
We strive to offer a first-class customer service experience
Our extensive range of captive screws is precision made and finished to the highest standards. We manufacture our products in the south of England and export them all over the world. We hold large volumes of captive screws in stock and can usually offer extremely quick turnaround times with same-day shipping as standard once an order is placed. Full export documentation is always provided for overseas customers. Our friendly customer service team is on hand to help you find the product which will make your designs come to life!
FAQs
What are Captive Screws used for?
A vital industrial component providing permanent fastening, captive screws are used when fasteners must remain attached to equipment (typically a panel) that is removed from its parent mating component. Captive screws are suitable for a range of applications, but are most often found in highly precise engineering environments..Captive screws offer higher levels of safety compared to conventional screws.
Are Captive Screws easy to install?
Captive screws are easy to install and are usually used with a retaining flange or a retaining washer. To install a captive screw using a retaining flange the flange must first be pressed onto the panel. The captive screw should then be screwed into the flange until the reduced diameter section is reached. For installation using a retaining washer the captive screw must firstly be fed through a hole in the panel. The washer is then screwed onto the captive screw, ensuring the reduced diameter section is reached.
Captive Screws vs Regular Screws
What is the difference?
Regular screws or fasteners are either fully threaded or have a plain unthreaded section which is the same diameter as the remaining thread of the screw. On a captive screw the middle section has a reduced diameter which is important to its functionality. Captive screws are used where it is important for the screw to be retained where a regular fastening could be taken out fully and lost either inside existing equipment, or on the floor and not found compromsing the safety of the euipment as a whole.
