Metric Flat Head Socket Cap Screw Dimensions & Size Chart | Maker

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Metric Flat Head Socket Cap Screw Dimensions & Size Chart
— Engineer-Grade Precision, Factory-Direct Value

Tired of mismatched fasteners that fail inspection? Get the complete metric flat head socket cap screw dimensions chart with公差, grade, and material data — trusted by 500+ OEMs in 30+ countries. Reduce sourcing errors, cut costs, and spec with confidence.

📥 Get Free Quote in 24h 📋 Download Size Chart PDF

⭐ Factory-direct pricing · ISO 9001:2015 · Free samples for qualified engineers

📑 Table of Contents

1. Common Sourcing Pain Points 2. Complete Size Chart 3. Technical Specs & Materials 4. Applications 5. Manufacturing Excellence 6. Social Proof 7. FAQ 8. Reviews 9. Get Started

⚠️ Why 1 in 3 Procurement Managers Get Fastener Specs Wrong

In 2025, a German automotive Tier-1 supplier lost €47,000 in rework because a flat head socket cap screw had a 0.2 mm head height deviation. You don’t have that margin for error.

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Inconsistent Dimensions

Head diameter varies ±0.3 mm across suppliers → assembly line jams.

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Hidden Cost Overruns

Low-cost fasteners fail torque testing → 23% scrap rate on prototypes.

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Shipping Delays

Mixed metric/imperial batches cause customs holds — 5–8 day delays.

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Certification Gaps

No traceable ISO/CE docs → rejected by QA on arrival.

The fix? A single, authoritative metric flat head socket cap screw dimensions chart backed by a factory that guarantees every micron.

📐 Complete Metric Flat Head Socket Cap Screw Dimensions & Size Chart

Below is the standard ISO 10642 / DIN 7991 compliant size chart for metric flat head socket cap screws (also known as countersunk hex socket screws). All values in mm unless noted. Use this chart to spec your next order with zero ambiguity.

Thread Size (M)	Pitch (mm)	Head Diameter dk (max)	Head Height k (max)	Hex Key Size s (mm)	Socket Depth t (min)	Drill Ø for Csk
M3	0.5	6.0	1.7	2.0	1.2	3.2
M4	0.7	8.0	2.3	2.5	1.6	4.3
M5	0.8	10.0	2.8	3.0	2.0	5.4
M6	1.0	12.0	3.3	4.0	2.4	6.6
M8	1.25	16.0	4.4	5.0	3.2	9.0
M10	1.5	20.0	5.5	6.0	4.0	11.0
M12	1.75	24.0	6.6	8.0	4.8	13.0
M16	2.0	30.0	8.8	10.0	6.4	17.5
M20	2.5	36.0	11.0	12.0	8.0	22.0

📌 Tolerances per ISO 10642: dk ±0.3 mm, k ±0.2 mm. Full chart includes M2–M24 available on request.

🔩 Mechanical & Material Grades

Grade	Material	Tensile Strength (MPa)	Hardness (HRC)	Corrosion Resistance	Typical Use
12.9	Alloy Steel	1220	39–44	Medium (Zn/Ni plating)	Automotive, aerospace
10.9	Carbon Steel	1040	32–39	Medium (Zn plating)	Industrial machinery
A2-70	SS 304	700	≤ 22	⭐⭐⭐⭐ High	Food, medical, marine
A4-80	SS 316	800	≤ 26	⭐⭐⭐⭐⭐ Very High	Chemical, offshore

✅ All grades available — we stock 12.9, 10.9, A2-70, A4-80 and custom alloys. Free material certification included with every batch.

⚙️ Key Performance Specs

🔹 Thread tolerance: 6g (ISO 965)
🔹 Surface finish: Black oxide, Zn plating, HDG, passivated
🔹 Head angle: 90° ± 1° (countersunk)
🔹 Max length: 200 mm (custom up to 400 mm)
🔹 Testing: 100% torque & hardness batch test
🔹 Packaging: Bulk boxes, poly bags, labeled per customer spec

📏 Length Availability (M3–M20)

📌 Standard lengths: 6, 8, 10, 12, 16, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, 100 mm
📌 Increments: 5 mm up to 100 mm, 10 mm above
📌 Custom lengths: ±0.5 mm tolerance, MOQ 500 pcs
📌 Partial thread: Available per DIN/ISO or customer drawing

🔧 Pro tip: For countersunk applications, match drill Ø to the 90° head angle for a flush finish.

🏭 Where Metric Flat Head Socket Cap Screws Are Used

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Automotive

Engine components, brake systems, interior trim

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Industrial Machinery

Gearboxes, pumps, conveyor systems

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Energy & Solar

PV mounting, wind turbine internals

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Construction

Steel structures, handrails, facade systems

💡 Case in point: A French agricultural machinery maker replaced their 8.8 grade bolts with our 12.9 flat head screws and reduced fastener weight by 18% while improving joint fatigue life by 32%. Read the full case study →

🏭 From Our Factory to Your Assembly Line

At Handan Boen Fastener Manufacturing Co., Ltd. (est. 2010), we produce metric flat head socket cap screws on CNC cold-forming lines with real-time laser gauging. Every batch is traceable from raw material (imported SAE 10B21, 42CrMo4, SS 304/316) to final torque test.

✅ 10+ years export experience
✅ 30+ countries served across Europe, Americas, SEA
✅ ISO 9001:2015 certified quality system
✅ Factory-direct pricing — save 15–25% vs. distributors

📞 +86 15630072814 | shuan@fastenboen.com

CNC cold-forming line, Handan factory

🤝 Trusted by Global Engineering Teams

“We switched to Boen for M6×20 flat head screws. Torque failure dropped from 4.2% to 0.3%. Their dimension chart is spot-on.”

— Lars, Senior Buyer, Danish Industrial Components

“The metric socket head cap screw size chart from Boen saved us 3 weeks of back-and-forth. We ordered 50k pieces — all within spec.”

— María, Procurement Manager, Spanish Automotive Tier-1

“Consistent 12.9 grade, fast lead time, and they actually answer the phone. Our new default supplier for metric fasteners.”

— Andrew, Engineering Director, UK Machinery OEM

❓ Frequently Asked Questions

What are the standard metric flat head socket cap screw dimensions?

Per ISO 10642, head diameter (dk) ranges from 6.0 mm (M3) to 36.0 mm (M20), with head height (k) from 1.7 mm to 11.0 mm. See our full chart above for all M3–M20 values.

What is the difference between DIN 7991 and ISO 10642?

ISO 10642 has slightly tighter tolerances on head diameter and socket depth. DIN 7991 is older but still used. We stock both and can advise based on your application.

Do you offer custom lengths or non-standard sizes?

Yes. Custom lengths from 5 mm to 400 mm, with ±0.5 mm tolerance. MOQ from 500 pcs. We also support custom head markings and packaging.

What is the lead time for a typical order?

Standard stock sizes: 7–12 days. Custom production: 18–25 days. Express shipping available for urgent orders (DHL, FedEx).

Do you provide free samples for qualification?

Yes. We offer free samples (up to 10 pcs per size) for qualified engineers and procurement managers. You only pay shipping.

What certifications come with your metric flat head screws?

ISO 9001:2015, CE, RoHS. Material certificates (EN 10204 3.1) and test reports are included with each shipment.

How do I place an order for metric socket head cap screws?

Email us at shuan@fastenboen.com or use the contact form. Provide thread size, length, grade, finish, and quantity. We’ll send a proforma invoice within 4 hours.

⭐ What Our Customers Say

“We’ve been sourcing M8×30 flat head screws from Boen for 2 years. Zero defects, consistent hardness, and their logistics team always keeps us updated.”

— Thomas, Purchasing Lead, German Automation GmbH

“The metric socket head cap screw size chart is the most accurate I’ve seen. We reduced our inspection time by 40%.”

— Elena, Quality Engineer, Italian Robotics

“Boen’s factory-direct pricing saved us 22% on our annual fastener spend. The quality is as good as European brands.”

— James, Supply Chain Manager, US Construction Equipment

✍️ About the Author — David Chen

David is a Senior Fastener Engineer at Handan Boen Fastener with 14 years of experience in metric and imperial fastener design, manufacturing, and quality control. He has authored over 40 technical guides for engineering teams across Europe and North America, and regularly speaks at industry conferences on fastener standardization and procurement best practices.