DIN 7991 / ISO 10642
DIN 7991 / ISO 10642 are metric screws with a flat countersunk head and internal hexagon drive. With a correctly prepared countersink, the head can sit approximately flush with the component surface.
DIN 7991 is the traditional designation that was replaced by ISO 10642. Head dimensions, head height, thread lengths and diameter ranges differ between editions, so complete interchangeability must not be assumed without checking the drawing.
The materials, property classes, finishes and lengths below describe possible manufacturing and supply programmes. They do not confirm JENPEX stock for a specific combination.
Technical specification
- Standard
- DIN 7991 / ISO 10642
- Technical name
- Hexagon socket countersunk head screw
- Head type
- Flat countersunk head, 90° to 92°
- Drive
- Internal hexagon
- Thread
- Metric coarse thread; ISO 10642:2026 covers M2 to M20
- Materials for enquiry
- Steel / A2 stainless steel / A4 stainless steel
- Steel property classes
- 8.8 / 10.9 / 12.9; ISO 10642:2026 markings 08.8 / 010.9 / 012.9
- Steel finishes
- Black oxide, zinc plated or another industrial finish depending on version
Material versions
Steel
For engineering joints with specified strength. Property class and surface finish are selected separately.
A2 stainless steel
Corrosion-resistant material for general industrial and indoor environments.
A4 stainless steel
Material with increased resistance in more demanding or chloride-bearing environments.
Steel screw property classes
8.8 / 08.8
Steel version for standard-strength engineering joints.
10.9 / 010.9
Steel version for more highly loaded engineering joints.
12.9 / 012.9
High-strength steel version for demanding industrial applications.
Important: the countersunk head has reduced loadability because of its geometry. ISO 10642:2026 specifies head loadability at 80% of thread loadability and requires a leading zero in the property-class marking. Not every size is available in every class and material.
Steel surface finishes
Surface finish is a separate property and must not be confused with the screw material. Depending on the version, steel screws may be supplied with:
- black oxide finish,
- electroplated zinc finish,
- other industrial surface finishes according to the joint requirements.
The finish, property class, size and quantity must be checked together.
DIN 7991 / ISO 10642 dimensions
The table gives the practical industrial range M3 to M20 according to ISO 10642: nominal thread d, theoretical maximum head diameter dk, maximum head height k, nominal internal hexagon s, minimum socket depth t and countersunk angle α.
| Thread d | dk theor. max. | k max. | Hexagon s | Depth t min. | Angle α |
|---|---|---|---|---|---|
| M3 | 6.72 | 1.86 | 2 | 1.10 | 90–92° |
| M4 | 8.96 | 2.48 | 2.5 | 1.40 | 90–92° |
| M5 | 11.20 | 3.10 | 3 | 1.75 | 90–92° |
| M6 | 13.44 | 3.72 | 4 | 2.20 | 90–92° |
| M8 | 17.92 | 4.96 | 5 | 2.90 | 90–92° |
| M10 | 22.40 | 6.20 | 6 | 3.50 | 90–92° |
| M12 | 26.88 | 7.44 | 8 | 4.30 | 90–92° |
| M14 | 30.80 | 8.40 | 10 | 4.50 | 90–92° |
| M16 | 33.60 | 8.80 | 10 | 4.80 | 90–92° |
| M20 | 40.32 | 10.16 | 12 | 5.60 | 90–92° |
Available lengths
The following guide shows selected spans found in manufacturer and supplier programmes. It is neither a complete normative matrix nor a statement of current JENPEX stock.
The range of manufactured and available lengths depends on diameter, material, property class and surface finish.
For a countersunk-head screw, nominal length L is the overall length including the head, measured from the flat top face to the screw end.
| Thread d | Indicative L range | Note |
|---|---|---|
| M3 | 6–30 mm | selected short lengths in supplier programmes |
| M4 | 6–40 mm | selected short to medium lengths |
| M5 | 8–60 mm | selected short to medium lengths |
| M6 | 8–70 mm | selected short to longer lengths |
| M8 | 12–100 mm | broad selection depending on material and class |
| M10 | 16–110 mm | broad selection depending on material and class |
| M12 | 20–110 mm | medium and longer versions |
| M14 | 25–110 mm | non-preferred ISO diameter; verify the exact combination |
| M16 | 25–130 mm | medium and longer versions |
| M20 | 40–140 mm | longer industrial versions |
Need a non-standard length?
Not every diameter, length, material and property-class combination is manufactured as a standard item.
If you cannot find the required size in the standard range, send us the thread diameter, required length, material or property class, quantity and required surface finish, if applicable. We will check availability, a suitable alternative or manufacturing possibilities.
DIN 7991 or ISO 10642?
DIN 7991 is the older designation, but it remains widely used in practice. ISO 10642 is the current international standard for this screw type; the current edition is ISO 10642:2026.
JENPEX therefore uses the combined designation DIN 7991 / ISO 10642, so buyers can find the product under either standard.
The designations are not completely interchangeable without checking head dimensions, countersink, thread length and the reduced-loadability marking.
Applications
The countersunk head allows a joint with a minimally projecting screw head when the hole is correctly prepared and the head is aligned with the countersink bearing surface.
- mechanical engineering,
- manufacturing equipment,
- machines and process equipment,
- automotive assemblies,
- fixtures and structural assemblies,
- moulds and tools,
- machine servicing and maintenance.
Technical information
What is DIN 7991 / ISO 10642?
It is a metric screw with a flat countersunk head and internal hexagon drive for joints requiring a minimally projecting head.
Are DIN 7991 and ISO 10642 completely identical?
No. They differ mainly in head dimensions, some thread lengths, the diameter range and the property-class marking.
How is nominal length measured?
For a countersunk-head screw, nominal length includes the head and is measured from the top face to the screw end.
Is every size available in property classes 8.8, 10.9 and 12.9?
No. ISO 10642:2026 uses the markings 08.8, 010.9 and 012.9 for reduced loadability, and supply depends on the specific version.
What is the difference between material and surface finish?
Steel, A2 and A4 identify material versions. Black oxide, zinc plating and other industrial coatings are separate finishes selected mainly for steel screws.
Related catalogue sections
Looking for a specific DIN 7991 / ISO 10642 size?
Send us the required size, material or steel property class, quantity and requested surface finish. We will check availability or a suitable alternative.
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