Metric Flat Head Socket Pipe Plugs (DIN 908) — Stainless Steel A2 (SUS304)

FULLERKREG DIN 908 metric flat head socket pipe plugs are manufactured from A2 stainless steel (SUS304) to Grade A2-70, with a whitened and passivated surface finish. The flat (parallel) metric thread combined with the flat sealing face requires a copper or aluminium sealing washer (not included) to achieve a pressure-tight seal — making these plugs ideal for hydraulic systems, pneumatic equipment, machine tools, and fluid power applications where a reusable, leak-free port closure is required.

The internal hexagon (Allen key) drive allows installation and removal in recessed or confined spaces where a standard hex head plug cannot be accessed.

---

Product Specifications

Standard	DIN 908
Thread Type	Metric straight (parallel) thread per ISO 261 / DIN 13
Head Type	Flat head (flush) with internal hexagon (Allen key) drive
Sealing Method	Flat face — requires copper or aluminium sealing washer (DIN 7603)
Material	A2 Stainless Steel / SUS304 / 1.4301
Grade	A2-70
Surface Finish	Whitened & Passivated
Size Range	M10 × 1 — M52 × 2
Drive Tool	Internal hexagon (Allen key) per ISO 2936
Related Standard	DIN 906 (tapered thread socket plug)  |  DIN 910 (hex head pipe plug)

---

Product Gallery

[Product Photo 1]

[Product Photo 2]

[Product Photo 3]

[Product Photo 4]

---

Dimensional Data — DIN 908 Metric Socket Pipe Plugs

All dimensions in millimeters (mm). Data per DIN 908 standard. Verify against current standard before use in safety-critical applications.

Thread (d)	Pitch (mm)	s — A/F (mm)	e — A/C (mm)	k — Head Height (mm)	t — Socket Depth (mm)	Sealing Ø (mm)
M10	1.0	17	19.6	4	3	10
M12	1.5	19	21.9	5	4	12
M14	1.5	22	25.4	5	4	14
M16	1.5	24	27.7	6	5	16
M18	1.5	27	31.2	6	5	18
M20	1.5	30	34.6	7	6	20
M22	1.5	32	36.9	7	6	22
M24	2.0	36	41.6	8	6	24
M26	1.5	36	41.6	8	6	26
M27	2.0	41	47.3	8	6	27
M30	2.0	46	53.1	9	8	30
M33	2.0	50	57.7	10	8	33
M36	2.0	55	63.5	10	8	36
M38	1.5	55	63.5	10	8	38
M42	2.0	65	75.1	12	10	42
M45	2.0	70	80.8	12	10	45
M48	2.0	75	86.6	14	12	48
M52	2.0	80	92.4	14	12	52

* s = across flats (A/F); e = across corners (A/C); k = head height; t = minimum socket depth. All dimensions per DIN 908. For full tolerance tables refer to the complete standard.

---

Allen Key (Hex Key) Size Reference

Thread	M10	M12	M14	M16	M18	M20	M22	M24	M27	M30	M33	M36	M42	M48	M52
Hex Key (mm)	14	17	19	22	24	27	30	32	36	41	46	50	55	65	70

---

Material & Grade Properties

Property	Value
Material Designation	A2 / SUS304 / 1.4301 / 0Cr18Ni9
Property Class	A2-70
Tensile Strength (Rm)	≥ 700 MPa
0.2% Proof Stress (Rp0.2)	≥ 450 MPa
Hardness	≤ 250 HV
Corrosion Resistance	Good — suitable for general outdoor, food, and mild chemical environments
Magnetic	Slightly magnetic after cold working
Surface Finish	Whitened & Passivated (electropolished appearance)
Temperature Range	−50°C to +300°C (continuous service)

---

Sealing & Installation Notes

• Thread type: Metric straight (parallel) — does NOT self-seal. A sealing washer is mandatory for pressure-tight installation.
• Recommended sealing washer: Copper (DIN 7603 Form A) or aluminium sealing washer — sized to match thread diameter.
• Torque: Apply recommended torque per thread size. Over-torquing may damage the sealing face or thread.
• PTFE tape: Not recommended as primary sealant for metric straight thread — use a proper sealing washer.
• Re-use: Replace sealing washer on each re-installation to ensure leak-free seal.
• Drive tool: Use a correctly sized, high-quality hex key or hex bit socket. Worn or undersized keys risk rounding the socket.
• Thread engagement: Ensure full thread engagement before torquing to avoid cross-threading.

---

DIN 908 vs DIN 906 vs DIN 910 — Which Plug to Choose?

Feature	DIN 908 (This Product)	DIN 906	DIN 910
Drive	Internal hex (Allen key)	Internal hex (Allen key)	External hex (wrench)
Thread	Metric straight (parallel)	Metric tapered / BSPT	Metric straight / BSPP
Sealing	Flat face — sealing washer required	Taper thread self-seals	Flat face — sealing washer required
Head Profile	Flat / flush head	Flat / flush head	Raised hex head
Access	Recessed / confined spaces	Recessed / confined spaces	Open access required
Re-usability	High — replace washer each time	Good — PTFE tape on re-use	High — replace washer each time
Typical Use	Hydraulic manifolds, machine tools, metric ports	General fluid sealing, metric & BSP ports	High-torque ports, open-access locations

---

Typical Applications

• 🔧 Hydraulic systems — sealing unused ports on manifolds, cylinders, and valve blocks
• 💨 Pneumatic equipment — closing unused ports on pneumatic valves, actuators, and fittings
• ⚙️ Machine tools & CNC equipment — sealing coolant and lubrication circuit ports
• 🏭 Industrial machinery — oil and fluid circuit port closures in stainless-required environments
• 🌊 Marine & food processing — where A2 stainless corrosion resistance is required

---

Frequently Asked Questions

Q: Does DIN 908 require a sealing washer?
A: Yes. DIN 908 uses a straight (parallel) metric thread with a flat sealing face. Unlike tapered thread plugs (DIN 906), it does not self-seal — a copper or aluminium sealing washer (DIN 7603) must be used to achieve a pressure-tight seal.

Q: What is the difference between DIN 908 and DIN 906?
A: DIN 906 uses a tapered thread (metric taper or BSPT) that self-seals through thread interference. DIN 908 uses a straight metric thread with a flat face seal — requiring a sealing washer but offering more precise thread engagement and easier re-use.

Q: What Allen key size do I need?
A: The hex key size equals the across-flats (s) dimension of the plug head. For example: M16 plug uses a 22mm hex key, M20 uses 27mm, M24 uses 32mm. See the Allen Key Size Reference table above.

Q: Is A2 stainless suitable for seawater applications?
A: A2 (SUS304) provides good general corrosion resistance but is not recommended for continuous seawater or high-chloride immersion. For marine and offshore applications, specify A4 (SUS316) grade instead.

Q: What pressure rating do DIN 908 plugs have?
A: Pressure rating depends on thread size, material, and installation quality. Consult your system engineer for application-specific pressure ratings. FULLERKREG can provide material test reports on request.