M1.6 M2 M2.5 M3 M4 Black Socket Countersunk Allen Head Bolts Grade 10.9 carbon steel Socket Screws - HomeDIYer
M1.6 M2 M2.5 M3 M4 Black Socket Countersunk Allen Head Bolts Grade 10.9 carbon steel Socket Screws - HomeDIYer
M1.6 M2 M2.5 M3 M4 Black Socket Countersunk Allen Head Bolts Grade 10.9 carbon steel Socket Screws - HomeDIYer
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M1.6 M2 M2.5 M3 M4 Black Socket Countersunk Allen Head Bolts Grade 10.9 carbon steel Socket Screws - HomeDIYerM1.6 M2 M2.5 M3 M4 Black Socket Countersunk Allen Head Bolts Grade 10.9 carbon steel Socket Screws - HomeDIYerM1.6 M2 M2.5 M3 M4 Black Socket Countersunk Allen Head Bolts Grade 10.9 carbon steel Socket Screws - HomeDIYer

M1.6 M2 M2.5 M3 M4 Black Socket Countersunk Allen Head Bolts Grade 10.9 carbon steel Socket Screws

HomeDIYer
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By HomeDIYer®

Thread SizexPitch: M1.6x0.35mm
Length: 4mm
Colour/Finish: Black
Price:
$0.75 USD
Stock:
In stock (100 units), ready to be shipped

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Description

Black Socket Countersunk Allen Head Bolts — Precision Fastening for Demanding Applications

When a loose fastener means a failed assembly, engineers and makers reach for a bolt they can trust. These M1.6–M4 black socket countersunk screws are built for professionals who need flush, secure, and corrosion-resistant fastening in tight spaces — from robotics enclosures to automotive panels.

Machined from Grade 10.9 high-strength carbon steel and finished with a black oxide coating, each screw features a precision countersunk head and a hex socket drive. Available in thread sizes M1.6, M2, M2.5, M3, and M4, with lengths ranging from 3 mm to 50 mm (approximately 0.12 in to 1.97 in).

Ideal for electronics assembly, CNC machine frames, RC vehicle builds, optical instrument housings, and any application where a flush surface and reliable clamping force are non-negotiable.

✅ Compatible with standard metric hex keys (Allen wrenches) and hex-bit drivers. Suitable for M1.6, M2, M2.5, M3, and M4 threaded holes per ISO 10642 countersunk socket screw standards.

Key Features

  • 🔩 Grade 10.9 Carbon Steel Durability — Made from high-strength Grade 10.9 carbon steel, these Allen head bolts deliver exceptional tensile strength and fatigue resistance, ideal for industrial machinery, automotive components, and high-stress applications demanding reliability.
  • 🖤 Corrosion-Resistant Black Finish — Featuring a sleek black oxide coating, these screws resist rust, abrasion, and environmental wear, ensuring longevity and a professional appearance in both indoor and outdoor settings.
  • 📐 Precision Countersunk Head Design — Engineered with a flush-mount countersunk head, these bolts sit seamlessly flat on surfaces, eliminating protrusions for streamlined assemblies in tight spaces or high-clearance equipment.
  • 🔬 Versatile Miniature Sizing (M1.6–M4) — Covering sizes from ultra-precise M1.6 to robust M4, this range excels in delicate tasks like electronics, robotics, and micro-mechanical systems, as well as compact machinery and automotive paneling.
  • 🔑 Hex Socket Accuracy & Reliability — Designed for secure Allen key engagement, the precision-machined hex socket minimizes stripping risks and ensures consistent torque control for fast, frustration-free installations every time.
  • 📦 Wide Length Selection — Available in lengths from 3 mm to 50 mm, giving you the exact grip length needed for thin panels, deep bores, and everything in between — no compromises on fit.

Who Is This For

🔧 DIY Makers & Hobbyists

Building a custom 3D printer frame, RC car chassis, or electronics enclosure? The flush countersunk head keeps your build clean and snag-free, while the hex socket gives you precise torque control even in confined spaces.

🏭 Engineers & Technicians

Assembling industrial machinery, optical instruments, or automation components where Grade 10.9 tensile strength and dimensional accuracy are mandatory — these screws meet the spec without compromise.

🚗 Automotive & Motorsport Builders

Securing interior panels, brackets, and lightweight components where a flush surface and vibration resistance matter. The black oxide finish blends seamlessly with dark trim and underbody hardware.

🎁 Workshop Stock & Maintenance Teams

Keep a full range of M1.6–M4 sizes on hand for rapid repairs and prototyping. The broad size matrix means fewer stock-outs and faster turnaround on the bench.

Technical Specifications

Thread Standard Metric (ISO)
Thread Sizes Available M1.6, M2, M2.5, M3, M4
Pitch M1.6×0.35 mm / M2×0.4 mm / M2.5×0.45 mm / M3×0.5 mm / M4×0.7 mm
Length Range 3 mm – 50 mm (varies by thread size)
Head Style Countersunk (Flat Head)
Drive Style Hex Socket (Allen / Internal Hex)
Material Carbon Steel
Grade / Property Class 10.9
Finish / Coating Black Oxide
Colour Black
Standard Reference ISO 10642 (DIN 7991)
Quantity See variant options

Frequently Asked Questions

What grade are these countersunk bolts?
These screws are Grade 10.9 carbon steel, which provides a minimum tensile strength of 1040 MPa — significantly stronger than the more common Grade 8.8 fasteners. They are suitable for high-stress and vibration-prone assemblies.
What size Allen key do I need?
The required hex key size varies by thread diameter: M1.6 typically uses a 0.7 mm key, M2 uses 1.5 mm, M2.5 uses 2 mm, M3 uses 2.5 mm, and M4 uses 3 mm. Always verify with a calibrated hex key set for best results.
Are these screws suitable for outdoor use?
The black oxide finish provides moderate corrosion resistance suitable for indoor and sheltered outdoor environments. For prolonged exposure to moisture, salt spray, or harsh chemicals, we recommend applying a light coat of oil or using stainless steel alternatives.
What is the countersink angle?
These screws conform to ISO 10642 (equivalent to DIN 7991), which specifies a 90° countersink angle. Ensure your mating material is drilled with a matching 90° countersink bit for a flush fit.
Can I use these in aluminium or plastic?
Yes. These screws are commonly used in aluminium extrusions, CNC-machined aluminium parts, and hard plastics such as acetal (Delrin) and nylon. For soft plastics, take care not to overtighten, as the countersunk head can crack brittle materials.
How do I choose the correct length?
For countersunk screws, the stated length includes the head. As a general rule, the engaged thread length should be at least 1× the thread diameter in steel, and 1.5–2× in softer materials like aluminium. Select a length that allows full thread engagement without bottoming out.
Are these RoHS compliant?
Black oxide is a conversion coating that does not contain restricted substances under RoHS directives. If your application requires a formal compliance certificate, please contact us to confirm.
Need a specific size or bulk quantity? Add your preferred variant to cart — or contact us if you need a size combination not listed above.

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