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Home / Screws / Grade 12.9 High Strength Black Nickel Internal Hex Screw Cylinder Head Extended Screw Bolt M2.5M3M4M5M6M8

Attributes

Brand -
Category Standard Parts, Components & Industrial Consumables / Screws
Origin -
Material Grade Alloy Steel Grade 12.9
Surface Finish Black Nickel Plated
Drive Type Internal Hex (Allen)
Head Style Cylinder Head (Socket Cap)
Available Sizes M2.5, M3, M4, M5, M6, M8
Thread Pitch Standard Coarse Thread
Tensile Strength Minimum 1220 MPa
Application High-Stress Mechanical Assembly
Corrosion Resistance Moderate (Indoor Use Recommended)
Package Type Bulk Box or Individual Packs

6 reviews

A

Anonymous

Mar 28, 2026

Rating: 5/5

Perfect fit

Ordered the M5 size and they fit precisely into my pre-drilled holes. The extended length option was very helpful for my specific setup.

A

Anonymous

Mar 20, 2026

Rating: 5/5

Excellent quality for high-torque applications

These bolts are exactly what I needed for my CNC machine assembly. The Grade 12.9 rating holds up well under significant torque without stripping the hex drive.

A

Anonymous

Mar 18, 2026

Rating: 4/5

Good value, fast shipping

The black nickel finish looks professional and matches my project aesthetics. One bolt had a slightly imperfect thread, but the rest of the batch was perfect.

A

Anonymous

Mar 17, 2026

Rating: 5/5

Strong and durable

Used these for a custom bicycle frame modification. They handle the vibration and stress perfectly. Highly recommend for serious builders.

A

Anonymous

Mar 16, 2026

Rating: 5/5

Repeat purchase for a reason

I've ordered these three times now for various automotive projects. They never fail, and the consistency in sizing is impressive.

A

Anonymous

Mar 08, 2026

Rating: 4/5

Solid hardware

Very strong screws. Just make sure you use a high-quality Allen key, as cheaper tools might round off the socket if you apply too much force.

5 FAQ

Q: What is the maximum torque rating for the M6 size?

A: For an M6 Grade 12.9 bolt with standard lubrication, the recommended tightening torque is approximately 10-12 Nm. Please refer to specific engineering tables for your exact application requirements.

Q: Is the head height standard for socket cap screws?

A: Yes, our cylinder head dimensions adhere to ISO 4762 standards, ensuring compatibility with standard sockets and fittings for the respective metric sizes.

Q: Can I return unopened boxes if I ordered the wrong size?

A: Absolutely. We accept returns on unopened packaging within 30 days of delivery. Please initiate a return request through your order history page.

Q: Are these screws suitable for outdoor use in rainy conditions?

A: While the black nickel plating offers some protection, Grade 12.9 alloy steel is prone to rust in prolonged wet environments. We recommend using them indoors or applying additional corrosion protection for outdoor use.

Q: Do you sell matching washers for these bolts?

A: Yes, we carry hardened steel washers compatible with Grade 12.9 fasteners. Please search our store for 'Grade 12.9 Washers' to find the matching sizes for your order.

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