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Home / Screws / Grade 12.9 Black Oxide Socket Head Cap Screws Cylindrical Head High-Strength Cup Head Bolts M3 M4 M5 M6 M8 M10 M12

Attributes

Brand -
Category Standard Parts, Components & Industrial Consumables / Screws
Origin -
Material Grade Alloy Steel Grade 12.9
Surface Finish Black Oxide Coating
Head Style Socket Head Cap (Cylindrical)
Drive Type Internal Hex (Allen)
Thread Standard ISO Metric Coarse
Available Sizes M3, M4, M5, M6, M8, M10, M12
Tensile Strength Minimum 1220 MPa
Yield Strength Minimum 1100 MPa
Hardness 39-44 HRC
Application High-stress machinery and automotive assembly

6 reviews

A

Anonymous

Mar 25, 2026

Rating: 4/5

Solid industrial fasteners

Very strong bolts. The hex socket is deep enough to get good leverage. Only minor issue was a slight variation in the black coating shade, but it doesn't affect performance.

A

Anonymous

Mar 22, 2026

Rating: 5/5

Excellent quality for high-torque applications

These bolts are exactly what I needed for my CNC machine rebuild. The black oxide finish is uniform, and they held up perfectly under high torque without stripping.

A

Anonymous

Mar 14, 2026

Rating: 4/5

Good bolts, packaging could be better

The screws themselves are top-notch and fit perfectly. However, some of the smaller M3 sizes were a bit loose in the bag. Still recommend for the quality.

A

Anonymous

Mar 11, 2026

Rating: 5/5

Perfect for automotive suspension work

Used these on my suspension setup. The high tensile strength gives me peace of mind knowing they won't shear under stress. Will buy again.

A

Anonymous

Mar 05, 2026

Rating: 5/5

Consistent sizing and threading

Ordered a mix of M6 and M8. Every single bolt threaded smoothly into tapped holes. No cross-threading issues at all.

A

Anonymous

Mar 04, 2026

Rating: 5/5

True Grade 12.9 strength

I tested a sample batch, and the hardness matches the specifications for Grade 12.9 steel. Great value for professional-grade fasteners.

5 FAQ

Q: Are these bolts suitable for outdoor use?

A: While the black oxide coating offers some corrosion resistance, these are best used in indoor or controlled environments. For harsh outdoor conditions, we recommend stainless steel or zinc-plated variants.

Q: Can I use these on aluminum parts?

A: Yes, but please ensure you use the correct torque settings to avoid galling or stripping the aluminum threads. Using a thread locker is also advisable.

Q: What size Allen key do I need for the M8 bolts?

A: For standard ISO metric M8 socket head cap screws, you will typically need a 6mm Allen key (hex wrench).

Q: What is the return policy if the size is wrong?

A: We accept returns within 30 days for unused items in original packaging. Please contact our customer service team to initiate a return request.

Q: Do these come with washers included?

A: No, these are sold as standalone bolts. Washers and nuts are available separately in our hardware section.

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