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This guide is for professionals, makers, and DIY enthusiasts seeking durable and aesthetically pleasing fasteners. The key benefit is a secure, flush finish for a clean look, with a potential caveat being the specific measurement method for countersunk bolts. These M6 x 16mm black oxide bolts are constructed from high-tensile carbon steel (Grade 10.9) and conform to DIN 7991 / ISO 10642 standards, featuring a hex socket drive for easy installation and a corrosion-resistant black oxide finish. They are ideal for furniture assembly, machinery, and bicycle applications where a low-profile, strong fastening solution is required.
| Colour | Black |
|---|---|
| Model Part Number | M6 X 16mm |
| Brand | DIYUK |
Unlike cap head screws, the length of a countersunk bolt is measured from the very top of the flat head down to the tip of the screw. Always measure the total length, including the head, when selecting countersunk bolts.
For an M6 size bolt with a hex socket drive, the standard Allen key (hex wrench) size required is 5mm.
Black oxide is a conversion coating that provides mild corrosion resistance and a matte black appearance. It is not as robust as plating or stainless steel but is suitable for many indoor and protected outdoor applications. It can wear down with friction or abrasion.
These bolts offer moderate corrosion resistance due to their black oxide finish. They are suitable for dry outdoor conditions. For prolonged exposure to rain, salt, or high humidity, stainless steel fasteners are recommended for better longevity.
Grade 10.9 is a high-strength metric fastener standard, indicating a minimum tensile strength of 1000 MPa and a minimum yield strength of 900 MPa. This makes them significantly stronger than standard Grade 8.8 bolts.
A countersunk head allows the bolt to sit flush with or below the surface of the material it's fastening. This creates a smooth, clean finish, prevents snagging, and is often preferred for aesthetic reasons or when components need to move freely over the fastener.
Yes, carbon steel bolts with a black oxide finish are typically magnetic.
Ensure the hole is properly countersunk to a 90° angle and the correct diameter for an M6 countersunk head. Verify you are using the correct bolt length; the total length includes the head.
Use a high-quality Allen key of the correct size (5mm for M6). Ensure the key is fully inserted into the socket. Apply steady, even pressure. If the socket is already damaged, the bolt may need to be carefully removed using alternative methods.
Confirm you are using an M6 threaded hole or nut. Check that the hole is not damaged or cross-threaded. Ensure the bolt is aligned straight before tightening.
The black oxide finish offers moderate corrosion resistance. For highly corrosive environments, consider using stainless steel fasteners. Clean affected areas gently and apply a light oil or protectant if the bolt is to remain in service.
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