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OnBuy.com£7.48Visit shop Black Countersunk Hex Socket Bolts Din 7991 Iso 10642 Grade 10.9 Allen Key Flat Head Screws M4 To M8 5056826614315
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B&Q£9.78Visit shop B&Q - M4 X 12mm Black Hex Socket Countersunk Bolts (Pack Of: 10) Din 7991 Flat Head Allen Screws
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These black oxide coated hex socket countersunk bolts from DIYUK are designed for precision and durability, offering a secure, flush finish ideal for professionals, makers, and DIY enthusiasts. They are perfect for projects requiring a clean aesthetic, such as furniture assembly, 3D printer rigs, or automotive trim installation. A key consideration is their unique measurement system, where length includes the head, requiring careful attention during selection.
| Colour | Black |
|---|---|
| Model Part Number | 7991 / ISO 10642 |
| Brand | DIYUK |
Determine the thickness of the material you are joining and the required depth of the fastening. Remember countersunk bolts are measured by their *total* length, including the head. Select a bolt length that passes through your materials and engages sufficiently with the threaded hole or nut.
Grade 10.9 indicates a high-strength alloy steel. It signifies a minimum tensile strength of 1000 MPa and a yield strength of 900 MPa, offering excellent durability and load-bearing capacity.
The black oxide finish offers some corrosion resistance, making them suitable for short-term or protected outdoor use. For long-term exposure to elements, especially in coastal or high-humidity areas, stainless steel fasteners are generally recommended.
Countersunk (or flat head) bolts are designed to sit flush with the surface they are installed in, providing a smooth finish. Cap head (or socket head cap screws) have a cylindrical head that sits above the surface.
For M5 hex socket countersunk bolts, you will typically need a 4mm Allen key. Always double-check the specific tool size required for your chosen bolt diameter.
Gently wipe with a soft, dry or slightly damp cloth. Avoid using harsh chemicals or abrasive materials that could scratch or damage the finish. A light application of mineral oil can help maintain the finish and add protection.
Yes, carbon steel fasteners are typically magnetic.
Ensure the countersink hole is deep enough and wide enough for the bolt head. Check if the material is too hard and requires a larger pilot hole or a different countersink bit.
Verify you are using the correct size Allen key for the bolt's hex socket. Ensure the socket is clean and free from debris. If the socket is stripped, the bolt may need to be removed using alternative methods.
Check that the pilot hole is correctly sized and aligned. Ensure the threads on the bolt and in the receiving hole are clean and undamaged. Do not force the bolt; back it out and re-align if necessary.
The black oxide finish provides corrosion resistance but is not foolproof. Clean the bolt with a soft cloth and apply a thin layer of oil (e.g., WD-40 or a light machine oil) to inhibit further rust. For prolonged outdoor use, consider stainless steel alternatives.
Setup: Ensure you have the correct size Allen key (hex wrench) for the chosen bolt. Select a drill bit and countersink bit appropriate for the bolt's head diameter and the material you are fastening into. Drill a pilot hole, then use the countersink bit to create a recess for the bolt head to sit flush. Insert the bolt and tighten using the Allen key until snug.
Compatibility: These bolts conform to DIN 7991 / ISO 10642 standards, ensuring compatibility with standard metric nuts, threaded inserts, and tapped holes. They are compatible with most common materials including wood, plastics, and metals, provided appropriate pilot holes are used.
Sizing Note: Remember that countersunk bolt length is measured from the very top of the flat head to the tip of the screw. Always measure your required depth and ensure this total length is suitable for your application.
Care: To maintain the corrosion resistance of the black oxide finish, avoid prolonged exposure to moisture. If used in damp environments, consider applying a light coat of oil or wax periodically. Clean with a dry or slightly damp cloth; avoid abrasive cleaners.
