Product Description
M4 × 0.7mm A4 stainless-steel countersunk socket screws, currently available in a 40mm length and manufactured to the traditional DIN 7991 countersunk socket pattern.
These corrosion-resistant metric screws feature a flat countersunk head and an internal 2.5mm hexagon drive. When installed into a correctly formed countersink, the head can sit flush with or below the surrounding surface, making them suitable for marine equipment, machinery, panels, brackets, fabrication and general engineering assemblies.
- Thread size: M4
- Thread pitch: 0.7mm metric coarse
- Available length: 40mm
- Threading: Part threaded according to the existing product description – verify stock
- Head style: Flat countersunk socket head
- Head diameter: Approximately 8mm
- Head height: Approximately 2.3mm
- Drive type: Internal hexagon / Allen key
- Allen key size: 2.5mm
- Material: A4 stainless steel
- Comparable stainless type: Commonly associated with 316 stainless steel
- Finish: Natural stainless-steel finish
- Traditional standard: DIN 7991
- Current international standard: ISO 10642
- British adoption: BS EN ISO 10642
- Pack sizes available: 5, 10, 20, 50, 100, 250, 500 and 1000
These M4 countersunk socket screws are suitable for marine fittings, coastal equipment, machinery, covers, panels, brackets, automotive components, fabrication and general engineering applications.
The standard M4 × 0.7mm metric coarse thread must be used with a corresponding M4 nut, threaded insert or tapped hole. It is not interchangeable with M3, M5 or M4 metric fine thread forms.
The flat countersunk head is intended to fit into a matching countersunk recess so that the top of the screw sits flush with the surrounding component. The countersink angle, diameter and depth should be checked before installation to ensure that the head bears evenly against the mating surface.
Countersunk socket screws have reduced loadability compared with conventional cylindrical socket cap screws because the countersunk profile and internal hexagon recess reduce the amount of material in the head. They should not automatically be substituted for standard socket cap screws in highly loaded joints.
A4 stainless steel contains molybdenum and generally offers improved resistance to moisture, salt spray and many corrosive environments compared with A2 stainless steel. It is commonly selected for marine, coastal, exterior, food-processing and chemical-processing applications.
The term “marine grade” indicates improved corrosion resistance but does not mean that the fastener is immune to corrosion in every environment. Chemicals, temperature, crevices, surface contamination and contact with dissimilar metals can all affect service life.
Stainless-steel threaded fasteners can suffer from thread galling or cold welding, particularly when installed quickly, overtightened, fitted dry or used with a stainless-steel mating thread. A suitable anti-seize compound and controlled installation speed may help reduce this risk.
Use a correctly fitting 2.5mm Allen key or hex socket bit and ensure that it is fully inserted into the recess before applying torque. An undersized, worn or incorrectly seated tool may damage the internal drive.
Unlike raised-head screws, countersunk screw length is normally measured over the complete screw, including the countersunk head. The stated 40mm length should therefore be treated as the overall screw length.
Please note: DIN 7991 is the traditional designation. ISO 10642 is the current international standard for hexagon socket countersunk head screws, with BS EN ISO 10642 being the corresponding British adoption.
| A | B | C | D | E | F |
| 4mm | 40mm | 8mm | 2.3mm | 2.5mm | 0.7 |
Please Note: Specifications given are intended as a guide only. If critical to your project please check with us first.
