RS PRO Black, Self-Colour Steel Hex Socket Countersunk Screw, DIN 7991, M4 x 20mm

RS PRO hexagon socket countersunk screws are an excellent choice when you need a fastener to sit flush or below the surface of your material.
These popular metric thread countersunk screws are produced in 10.9 grade steel and are designed for light duty applications where space is limited. These fasteners have a black finish which ensures an attractive, quality appearance and finish wherever they are used.
These screws fasteners can be tightened or undone using an Allen key.

Various thread sizes available, including M3, M4, M5, M6, M8 and M16
Countersunk – the head does not stick out so that nothing can hit it and interfere with the operation of the application
Also used in many internal joinery applications
Have the marking on the head
More resilient than 8.8 grade
Nominal strength of 1040 N/mm²
Yield strength of 940 N/mm²
Requires a Hex key / Allen key

Although uses may vary, as standard, these screws are fasteners for industrial equipment or machines which requires parts to be fixed onto a surface or together. The socket will need to be the same metric thread as the screw itself. As an example, some of the types of uses would be:
Woodworking
Domestic applications
Fasteners and fixings
Machine tooling and repair
Security guarding
Panel Building
Electronic applications
Automotive industry
Medical applications
Facilities and maintenance applications

Socket screws are defined by their name. They are a type of threaded bolt which screws into the intended socket. There are various thread sizes and lengths and can be used for both industrial and personal purposes. Good quality and reliable RS PRO socket screws ensures the fixing will remain strong and stable, whatever the application.

Requires a Hex key
We offer a range of hexagon countersunk socket screws in black self-coloured steel, available in various thread sizes and lengths. Refer to the Datasheet and Range Overview download file for details.
If black oxide self-coloured steel is not what you are looking for we also offer steel hexagon countersunk socket screws with a BZP finish or alternatively A2 (306) and A4 (316) stainless steel.

Threaded in accordance with DIN 7991

Want to prevent screws from sticking out of your equipment or surfaces? Turn to this countersunk fastener from RS PRO. It has a high strength-to-weight ratio thanks to its stainless steel material, while the black oxide coating enhances its thickness and resistance to corrosion. This means it can withstand heavy-duty applications in tough industrial environments.


For fast and simple installation, use an Allen or hex key to tighten the screw. As it's small in size, it can easily fit into tight spaces. This type of screw is commonly used for domestic and commercial applications, including woodworking, DIY constructions and building panels.