Socket Screws & Bolts
Black Hex Socket Countersunk Bolts DIN 7991
Black Hex Socket Countersunk Bolts - DIN 7991 Grade 10.9
20% off applied
Overview
Countersunk hex socket bolts manufactured to DIN 7991, made from carbon steel to property class 10.9.
The defining feature is the head geometry: a conical 90° countersunk profile that seats flush with, or just below, the surrounding material once fully driven home, leaving a smooth, snag-free surface rather than a proud bolt head. Drive is via a fully recessed internal hexagon (Allen key) socket, so you can tighten the bolt with an Allen key, straight down the centre of the fastener – useful both for reaching full seating on a hard carbon-steel bolt and for working in a recess too shallow or tight for a spanner or screwdriver. The bolts have a black oxide finish.
Key Features
- Manufactured to DIN 7991
- Property class 10.9 carbon steel
- 90° conical countersunk head sits flush with, or below, the surrounding surface for a smooth, snag-free finish
- Fully recessed internal hexagon (Allen key) drive lets you tighten the bolt straight down the centre of the fastener, even in tight or recessed fixing points
- Black oxide finish
- Ten sizes covering M4 x 8mm up to M8 x 35mm, so light fixings and heavier-duty fastening are covered from the same range
- Pairs with a tapped hole, standard nut, or threaded insert of the matching metric thread
Specification
| Size | Head diameter | Head height | Hex socket (Allen key) size |
|---|---|---|---|
| M4 x 8mm (0.31in) | 8mm (0.31in) | 2.3mm (0.09in) | 2.5mm (0.10in) |
| M4 x 12mm (0.47in) | 8mm (0.31in) | 2.3mm (0.09in) | 2.5mm (0.10in) |
| M5 x 10mm (0.39in) | 10mm (0.39in) | 2.8mm (0.11in) | 3mm (0.12in) |
| M5 x 20mm (0.79in) | 10mm (0.39in) | 2.8mm (0.11in) | 3mm (0.12in) |
| M6 x 16mm (0.63in) | 12mm (0.47in) | 3.3mm (0.13in) | 4mm (0.16in) |
| M6 x 30mm (1.18in) | 12mm (0.47in) | 3.3mm (0.13in) | 4mm (0.16in) |
| M8 x 20mm (0.79in) | 16mm (0.63in) | 4.4mm (0.17in) | 5mm (0.20in) |
| M8 x 25mm (0.98in) | 16mm (0.63in) | 4.4mm (0.17in) | 5mm (0.20in) |
| M8 x 30mm (1.18in) | 16mm (0.63in) | 4.4mm (0.17in) | 5mm (0.20in) |
| M8 x 35mm (1.38in) | 16mm (0.63in) | 4.4mm (0.17in) | 5mm (0.20in) |
Sizing note: unlike dome or cap head screws, countersunk bolts are measured by their total length, including the head – measure from the flat top face of the head to the tip of the thread to confirm the correct length for your application.
Installation Guidance
Drill, punch or machine a countersink taper into the fixing material sized to match the bolt head, so it seats flush rather than standing proud or sinking below the surface. Drive with the correct size hex key for the bolt diameter – 2.5mm (0.10in) for M4, 3mm (0.12in) for M5, 4mm (0.16in) for M6, and 5mm (0.20in) for M8, as listed in the specification table above – and continue until the head is fully seated in the countersink. The bolt then pairs with a tapped hole, a standard nut, or a threaded insert of the matching metric thread on the far side of the joint.
Typical Applications
- Flat-pack furniture and cabinetry assembly, where a flush head avoids snagging on clothing, hands, or adjoining panels
- 3D printer and machine frame builds, where a compact, fully recessed drive suits enclosed or awkward-to-reach fixing points
- Electronics enclosures, where a smooth external profile matters for both appearance and safe handling
- General workshop and DIY fixing jobs needing a high-tensile, low-profile bolt that can be driven with a simple Allen key rather than a spanner
Order before 2pm Mon–Fri for same-day dispatch from our UK warehouse.
Specifications
| Material | Steel |
|---|---|
| Finish | Black oxide |
| Size | M4 x 8mm to M8 x 35mm |
| Weight | 0.0009 kg |
All 40 options and prices
| Size | Pack quantity | Price inc. VAT | ex. VAT | Per piece | Select |
|---|---|---|---|---|---|
| M4 x 8mm | 2 | £4.38 | £3.65 | £2.19 | Sold out |
| M4 x 8mm | 10 | £4.68 | £3.90 | £0.47 | Sold out |
| M4 x 8mm | 50 | £4.98 | £4.15 | £0.10 | Sold out |
| M4 x 8mm | 100 | £5.98 | £4.99 | £0.06 | Sold out |
| M4 x 12mm | 2 | £4.38 | £3.65 | £2.19 | |
| M4 x 12mm | 10 | £4.68 | £3.90 | £0.47 | |
| M4 x 12mm | 50 | £4.98 | £4.15 | £0.10 | |
| M4 x 12mm | 100 | £6.28 | £5.23 | £0.06 | |
| M5 x 10mm | 2 | £4.38 | £3.65 | £2.19 | |
| M5 x 10mm | 10 | £4.78 | £3.98 | £0.48 | |
| M5 x 10mm | 50 | £5.98 | £4.99 | £0.12 | |
| M5 x 10mm | 100 | £6.78 | £5.65 | £0.07 | |
| M5 x 20mm | 2 | £4.38 | £3.65 | £2.19 | |
| M5 x 20mm | 10 | £4.78 | £3.98 | £0.48 | |
| M5 x 20mm | 50 | £6.28 | £5.23 | £0.13 | |
| M5 x 20mm | 100 | £6.98 | £5.81 | £0.07 | |
| M6 x 16mm | 2 | £4.38 | £3.65 | £2.19 | |
| M6 x 16mm | 10 | £4.88 | £4.07 | £0.49 | |
| M6 x 16mm | 50 | £6.48 | £5.40 | £0.13 | |
| M6 x 16mm | 100 | £7.58 | £6.31 | £0.08 | |
| M6 x 30mm | 2 | £4.48 | £3.73 | £2.24 | |
| M6 x 30mm | 10 | £4.98 | £4.15 | £0.50 | |
| M6 x 30mm | 50 | £7.18 | £5.98 | £0.14 | Sold out |
| M6 x 30mm | 100 | £8.98 | £7.48 | £0.09 | Sold out |
| M8 x 20mm | 2 | £4.48 | £3.73 | £2.24 | |
| M8 x 20mm | 10 | £5.88 | £4.90 | £0.59 | |
| M8 x 20mm | 50 | £7.68 | £6.40 | £0.15 | Sold out |
| M8 x 20mm | 100 | £12.28 | £10.23 | £0.12 | Sold out |
| M8 x 25mm | 2 | £4.48 | £3.73 | £2.24 | |
| M8 x 25mm | 10 | £5.88 | £4.90 | £0.59 | |
| M8 x 25mm | 50 | £7.98 | £6.65 | £0.16 | |
| M8 x 25mm | 100 | £12.98 | £10.81 | £0.13 | |
| M8 x 30mm | 2 | £4.48 | £3.73 | £2.24 | |
| M8 x 30mm | 10 | £5.98 | £4.99 | £0.60 | |
| M8 x 30mm | 50 | £8.58 | £7.15 | £0.17 | |
| M8 x 30mm | 100 | £13.98 | £11.65 | £0.14 | |
| M8 x 35mm | 2 | £4.58 | £3.81 | £2.29 | |
| M8 x 35mm | 10 | £6.38 | £5.31 | £0.64 | |
| M8 x 35mm | 50 | £10.38 | £8.65 | £0.21 | |
| M8 x 35mm | 100 | £17.68 | £14.73 | £0.18 |
Delivery and returns
Free standard UK delivery, or Next Day Delivery for £0.99 (order by 2pm).
Order before 2pm Mon–Fri for same-day dispatch
60-day returns
Where to use it.
