Torx Countersunk Screws (GB/T 2673-2000 / ISO 14581) — Marine Stainless Steel A4

FULLERKREG Torx countersunk flat-head screws in A4 (SUS 316) marine-grade stainless steel are manufactured to GB/T 2673-2000 and ISO 14581 standards. Featuring a 90° countersunk head with an internal Torx (TX) drive, these screws deliver superior torque transmission, reduced cam-out risk, and a flush-mount finish. The molybdenum-enhanced A4 alloy provides outstanding resistance to chloride corrosion, making them the preferred choice for marine, coastal, chemical, and food-processing environments. Strength grade A4-70, surface: passivated & whitened.

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	A4 Marine Stainless Steel (SUS 316 / 1.4401)
Surface Treatment	Passivated & Whitened (Bright Finish)
Strength Grade	A4-70
Size Range	M2 – M10
Length Range	3 mm – 80 mm
Brand	FULLERKREG

Product Photo Gallery

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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)
M2	0.40	TX6	3.80	3.50	1.20	0.96	0.70	1.00	12	—
M2.5	0.45	TX8	4.70	4.40	1.50	1.21	0.85	1.20	14	—
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	—

* 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)
M2	3, 4, 5, 6, 8, 10, 12, 16, 20
M2.5	4, 5, 6, 8, 10, 12, 16, 20, 25
M3	4, 5, 6, 8, 10, 12, 16, 20, 25, 30
M4	5, 6, 8, 10, 12, 16, 20, 25, 30, 35, 40
M5	6, 8, 10, 12, 16, 20, 25, 30, 35, 40, 45, 50
M6	8, 10, 12, 16, 20, 25, 30, 35, 40, 45, 50, 55, 60
M8	10, 12, 16, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80
M10	16, 20, 25, 30, 35, 40, 45, 50, 55, 60, 70, 80

Selection Guide

Requirement	Recommendation
Marine / offshore / coastal environment	A4 (SUS 316) is the preferred grade — superior chloride resistance vs. A2
Flush surface finish required	Use countersunk head; ensure countersink angle matches 90°
High torque / anti-cam-out	Torx (TX) drive preferred over Phillips or slotted
Chemical / food processing environment	A4 (SUS 316) with passivated finish; excellent resistance to acids and chlorides
Swimming pools / desalination plants	A4-70 recommended; verify chloride concentration with engineer
Thin material / sheet metal assembly	Select shorter length; verify countersink depth vs. material thickness
Structural / high-load application	Verify A4-70 tensile strength meets design load; consult engineer

A4 vs. A2 — Why Choose Marine Grade?

Property	A2 (SUS 304)	A4 (SUS 316)
Base Alloy	18% Cr, 8% Ni	16% Cr, 10% Ni, 2% Mo
Molybdenum Content	None	2–3% (key for chloride resistance)
Chloride Resistance	Moderate	Excellent
Marine Suitability	Limited (mild coastal only)	Recommended for marine & offshore
Pitting Resistance (PREN)	~18–20	~24–26
Strength Grade	A2-70	A4-70
Min. Tensile Strength	700 MPa	700 MPa

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 designation: A4 (austenitic stainless steel, SUS 316 / 1.4401)
• Strength class: A4-70 (min. tensile strength 700 MPa for d ≤ M20)
• Surface: Passivated — enhanced corrosion resistance without additional coating

Material & Mechanical Properties

Property	A4-70 Value
Material Grade	A4 (SUS 316 / 1.4401)
Composition	16–18% Cr, 10–14% Ni, 2–3% Mo
Min. Tensile Strength (Rm)	700 MPa
Min. 0.2% Proof Stress (Rp0.2)	450 MPa
Min. Elongation (A)	40%
Hardness	220 HV max
Corrosion Resistance	Excellent — marine, coastal, chemical, food-grade, and chloride-rich environments
Magnetic	Slightly magnetic after cold working
Operating Temperature	-196°C to +300°C

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, 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; third-party inspection available.
🔬 Material Certified — Mill certificates (MTC) provided; A4 SUS 316 composition and Mo content verified per heat.
📦 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.