Torx Countersunk Screws (GB/T 2673-2000 / ISO 14581) — Alloy Steel Class 10.9, Black

FULLERKREG Torx countersunk flat-head screws in alloy steel 10B21, Class 10.9 are manufactured to GB/T 2673-2000 and ISO 14581 standards. Featuring a 90° countersunk head with an internal Torx (TX) drive, these high-strength screws deliver superior torque transmission, reduced cam-out risk, and a flush-mount finish. The black surface treatment (black oxide / black phosphate) provides a sleek appearance with moderate corrosion protection, making them ideal for machinery, automotive, tooling, and structural assemblies where high clamping force and a low-profile head are required.

Product Specifications

Attribute	Detail
Product Name	Torx Countersunk Flat Head Screws
Standard	GB/T 2673-2000 / ISO 14581
Drive Type	Torx (TX) Internal Drive
Head Type	Countersunk (Flat Head), 90° included angle
Material	Alloy Steel 10B21
Surface Treatment	Black (Black Oxide / Black Phosphate)
Strength Grade	Class 10.9
Size Range	M3 – M12
Length Range	6 mm – 100 mm
Brand	FULLERKREG

Product Photo Gallery

[ Photo 1 ]

[ Photo 2 ]

[ Photo 3 ]

[ Photo 4 ]

Dimensional Drawing

Per GB/T 2673-2000 / ISO 14581 — Countersunk head with 90° included angle, Torx recess depth t, head diameter dk, head height k, thread pitch p.

• Head angle: 90° (±1°)
• Torx recess: TX drive per ISO 10664
• Thread: Metric coarse thread per ISO 68-1
• Thread tolerance: 6g
• Head tolerance: h13

Dimensional Data

Thread d	Pitch p (mm)	TX Drive	Head Dia. dk max (mm)	Head Dia. dk min (mm)	Head Height k max (mm)	Head Height k min (mm)	Recess Depth t min (mm)	Recess Depth t max (mm)	Min. Thread Length b (mm)	Unit Weight (g / 100 pcs)
M3	0.50	TX10	5.60	5.30	1.65	1.35	1.00	1.40	16	—
M4	0.70	TX20	7.50	7.14	2.20	1.86	1.30	1.80	20	—
M5	0.80	TX25	9.20	8.84	2.50	2.16	1.50	2.10	22	—
M6	1.00	TX30	11.00	10.57	3.00	2.61	1.80	2.50	24	—
M8	1.25	TX40	14.50	14.07	4.00	3.54	2.30	3.20	28	—
M10	1.50	TX50	18.00	17.57	5.00	4.54	2.80	3.80	32	—
M12	1.75	TX55	22.00	21.48	6.00	5.48	3.30	4.60	36	—

* All dimensions in mm. Tolerances per GB/T 2673-2000 / ISO 14581. Unit weight (g/100 pcs) to be updated upon batch confirmation.

Standard Length Range by Diameter

Thread	Available Lengths (mm)
M3	6, 8, 10, 12, 16, 20, 25, 30
M4	6, 8, 10, 12, 16, 20, 25, 30, 35, 40
M5	8, 10, 12, 16, 20, 25, 30, 35, 40, 45, 50
M6	10, 12, 16, 20, 25, 30, 35, 40, 45, 50, 55, 60
M8	12, 16, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80
M10	20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, 100
M12	25, 30, 35, 40, 45, 50, 55, 60, 70, 80, 90, 100

Selection Guide

Requirement	Recommendation
High clamping force / high-strength joint	Class 10.9 alloy steel provides min. 1040 MPa tensile strength — ideal for structural and mechanical assemblies
Flush surface finish required	Use countersunk head; ensure countersink angle matches 90°
Anti-cam-out / high torque drive	Torx (TX) drive preferred over Phillips or slotted for power tool use
Aesthetic / low-visibility fastener	Black finish provides sleek appearance; suitable for exposed assemblies
Indoor / dry environment	Black oxide finish provides moderate corrosion resistance; apply oil or grease for enhanced protection
Automotive / machinery / tooling	Class 10.9 alloy steel is the standard choice for high-load mechanical joints
Outdoor / corrosive environment	Consider stainless steel A2 or A4 grades instead

Class 10.9 vs. Other Grades — Strength Comparison

Property	Class 8.8	Class 10.9	Class 12.9
Min. Tensile Strength (Rm)	800 MPa	1040 MPa	1220 MPa
Min. Proof Load Stress (Sp)	600 MPa	830 MPa	970 MPa
Min. Yield Strength (Rp0.2)	640 MPa	940 MPa	1100 MPa
Hardness (Vickers)	250–320 HV	320–380 HV	380–435 HV
Typical Application	General structural	High-strength mechanical	Ultra-high-strength / critical

Standard Reference

GB/T 2673-2000 is the Chinese national standard for countersunk head screws with Torx recess, technically equivalent to ISO 14581:2011. Key parameters defined by the standard:

• Head angle: 90° included angle (±1°)
• Drive recess: Torx (TX) per ISO 10664
• Thread: ISO metric coarse, tolerance class 6g
• Material: Alloy steel 10B21 (boron-alloyed, quenched & tempered)
• Strength class: 10.9 per ISO 898-1 (min. tensile strength 1040 MPa)
• Surface: Black oxide / black phosphate — moderate corrosion protection; oil treatment recommended for storage and outdoor use

Material & Mechanical Properties

Property	Class 10.9 Value
Material	Alloy Steel 10B21 (Boron-alloyed, Quenched & Tempered)
Min. Tensile Strength (Rm)	1040 MPa
Min. Proof Load Stress (Sp)	830 MPa
Min. Yield Strength (Rp0.2)	940 MPa
Min. Elongation (A)	9%
Hardness (Vickers)	320–380 HV
Surface Treatment	Black Oxide / Black Phosphate
Corrosion Resistance	Moderate — suitable for dry/indoor environments; oil recommended for storage
Magnetic	Yes (ferromagnetic)
Heat Treatment	Quenched & Tempered (Q&T)

Packaging & Supply

Item	Detail
Standard Pack	100 pcs / bag, 1,000 pcs / box (varies by size)
MOQ	100 pcs (standard sizes); custom quantities available
Labeling	Size, standard, material, grade, quantity — FULLERKREG brand label
Custom Packaging	Available on request (OEM / private label)
Lead Time	In-stock items: 1–3 business days; custom orders: 7–15 business days

Why FULLERKREG

🏭 Factory Direct — Manufactured in-house with full process control, no middlemen.
📐 Standard Compliant — Strictly per GB/T 2673-2000 / ISO 14581 and ISO 898-1; third-party inspection available.
🔬 Material Certified — Mill certificates (MTC) provided; 10B21 alloy composition and mechanical properties verified per batch.
📦 Bulk Ready — Wholesale quantities from 100 pcs to millions; competitive tiered pricing.
🌍 Global Shipping — Export experience to 30+ countries; DDP / FOB / EXW terms available.
🔧 Technical Support — Engineering team available for selection guidance, drawings, and custom specs.