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Black Hex Socket Countersunk Bolts - M8 X 20mm

Black Hex Socket Countersunk Bolts - M8 X 20mm

Upgrade your fasteners with professional-grade Black Oxide Bolts. Designed for precision and durab...

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Black Countersunk Hex Socket Bolts Din 7991 Iso 10642 Grade 10.9 Allen Key Flat Head Screws M4 To M8 5056826614322

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B&Q - M4 X 12mm Black Hex Socket Countersunk Bolts (Pack Of: 50) Din 7991 Flat Head Allen Screws

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OnBuy.comBlack Countersunk Hex Socket Bolts Din 7991 Iso 10642 Grade 10.9 Allen Key Flat Head Screws M4 To M8 5056826614322
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£7.88
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B&QB&Q - M4 X 12mm Black Hex Socket Countersunk Bolts (Pack Of: 50) Din 7991 Flat Head Allen Screws
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£10.38
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Product Information

Full details

This guide is for professionals, makers, and DIY enthusiasts seeking durable and aesthetically pleasing fasteners. The key benefit is a secure, flush finish ideal for projects requiring a clean look. A caveat to note is the specific measurement convention for countersunk bolts. These M8 x 20mm black oxide bolts are crafted from high-tensile carbon steel (Grade 10.9) for superior strength and feature a corrosion-resistant black oxide finish, complying with DIN 7991 / ISO 10642 standards.

All features

ColourBlack
Model Part NumberM8 X 20mm
BrandDIYUK

Extended Product Information

FAQs

How do I measure a countersunk bolt?

Countersunk bolts are measured by their total length, from the very top of the flat head down to the tip of the screw. This is different from cap head screws where the measurement is typically to the underside of the head.

What size Allen key do I need for M8 bolts?

For M8 size hex socket bolts, you will typically need a 5mm metric Allen key.

What does 'Grade 10.9' mean?

Grade 10.9 indicates a high-strength classification for steel bolts, signifying excellent tensile strength and durability, suitable for demanding applications.

Is the black oxide finish suitable for outdoor use?

The black oxide finish provides good corrosion resistance for indoor and moderate outdoor conditions. For prolonged exposure to harsh weather, additional protective measures may be beneficial.

Can I use these bolts in hard wood?

Yes, these bolts can be used in hardwood. Ensure you pre-drill a pilot hole and properly countersink the hole to accommodate the bolt's head for a flush finish.

What is the standard these bolts conform to?

These bolts conform to DIN 7991 and ISO 10642 standards, which specify dimensions and requirements for hexagon socket countersunk head cap screws.

Troubleshooting

Bolt head does not sit flush.

Ensure the hole is correctly countersunk to a 90° angle. The countersink depth may need to be adjusted.

Allen key is stripping the hex socket.

Verify you are using the correct size metric Allen key (5mm for M8). Ensure the key is fully inserted and the socket is free of debris. Do not overtighten.

Bolt feels loose after tightening.

Check that the threaded hole or nut is correctly sized and tapped for an M8 bolt. Ensure the material being fastened is sufficiently strong to hold the bolt.

Signs of rust or corrosion.

While the black oxide finish offers resistance, it is not entirely impervious. Clean the affected area and apply a protective coating like wax or a light oil.

Pros and Cons

Pros

  • High-strength material for reliable performance.
  • Corrosion-resistant finish for longevity.
  • Flush mounting capability for a clean aesthetic.
  • Standard drive type for easy installation.
  • Suitable for heavy-duty applications.

Cons

  • Requires a specific size Allen key for installation.
  • Black oxide finish can wear over time with extensive friction.
  • Countersunk design means the hole must be pre-drilled and countersunk.
  • Specific measurement convention requires careful attention.

Setup, Compatibility & Care

Setup:

  1. Hole Preparation: Ensure the material has a pre-drilled hole appropriately sized for an M8 bolt. Crucially, the hole must also be countersunk to a 90° angle to accommodate the bolt's head.
  2. Measurement: Verify the total length of the bolt (from the top of the head to the tip) is suitable for your material thickness. Remember, countersunk bolt length includes the head.
  3. Installation: Insert the bolt into the prepared hole. Use a suitable metric Allen key (typically 5mm for M8) to drive the bolt until it sits flush with the surface.

Compatibility:

  • Material: Designed for use in wood, plastic, metal, and other solid materials that can be drilled and countersunk.
  • Tools: Requires a standard 5mm metric Allen key.
  • Standards: Compatible with components designed for M8 bolts conforming to DIN 7991 / ISO 10642 standards.

Care:

  • Clean with a dry or slightly damp cloth. Avoid abrasive cleaners.
  • For extended outdoor use or in high-moisture environments, consider applying a light coat of lubricant or wax to the exposed threads to further enhance corrosion resistance.
  • Periodically check for tightness, especially in applications subject to vibration.

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