Automotion Components is a leading manufacturer of captive screws. Our captive screws can be produced to customer drawings and we can offer a wide range of materials and finishing options. We hold a large volume of captive screws in stock which means that we can usually offer same-day shipping from our warehouse in the UK.
What are captive screws?
Captive screws are designed to provide “captivation” (meaning a permanent hold). Captive screws can still be removed from their installation, but only intentionally - they are very unlikely to fall out accidentally once installed because 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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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.
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 below.
Captive screw material options
| 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. |
Our popular button head captive screw in marine grade stainless steel (A4/AISI 316 series). Also comes with a variety of different drive types, such as Phillips or TX (hexalobular).
Our countersunk captive screws offer an aesthetically pleasing flush finish when used in conjunction with a counterbored panel hole. Shown here with a black coating.
This titanium captive thumb screw is hand-tightenable, has a high strength:weight ratio, and is very resistant to corrosion. Available in ASTM B348 grade 2 and grade 5 titanium.
Our popular cap head captive screw is in stock in zinc-plated steel - a good combination of materials/finishing for a compromise between strength and corrosion resistance.
Materials
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. |
| 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. |
Special thin captive thumb screws with pointed end for easy location. Slot drive.
Thin headed captive thumb screw - shown here in titanium.
Cheese head hex drive captive screw. Slotted drive version available too.
Associated products
What is a retaining flange and how is it used?
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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Retainer flange for captive screw installation on thin, non-threaded panels.
Threaded captive washer for captive screw installation on non-threaded panels.
Why choose Automotion Components Ltd.'s 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 captive screws in stock and many 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.
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!
