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

FULLERKREG DIN 908 imperial BSPP flat head socket pipe plugs are manufactured from A2 stainless steel (SUS304) to Grade A2-70, with a whitened and passivated surface finish. These plugs feature British Standard Pipe Parallel (BSPP / G thread) — the straight parallel pipe thread widely used in hydraulic and pneumatic systems across the UK, Europe, Asia, and Commonwealth markets.

The A2 stainless steel construction provides excellent corrosion resistance for outdoor, marine-adjacent, food-grade, and chemical environments where carbon steel plugs would corrode. The flat head with internal hexagon (Allen key) drive allows installation in recessed or confined port locations. A bonded seal (Dowty washer) or O-ring face seal is required to achieve a pressure-tight connection.

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Product Specifications

Standard	DIN 908 (Imperial Pipe Thread — BSPP, Flat Head)
Thread Type	BSPP — British Standard Pipe Parallel (G thread) per ISO 228-1 / BS EN ISO 228
Thread Profile	Whitworth 55° thread form, parallel (straight) — does NOT self-seal
Head Type	Flat head (flush) with internal hexagon (Allen key) drive
Sealing Method	Flat face — requires bonded seal (Dowty washer) or O-ring face seal
Material	A2 Stainless Steel / SUS304 / 1.4301
Grade	A2-70
Surface Finish	Whitened & Passivated
Size Range	G1/8 — G2 (BSPP)
Drive Tool	Internal hexagon (Allen key) per ISO 2936
Key Advantage	Stainless corrosion resistance + BSPP thread — ideal for corrosive or hygienic environments with G-thread ports

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Dimensional Data — DIN 908 BSPP Flat Head Socket Pipe Plugs

All dimensions in millimeters (mm) unless noted. Thread sizes in BSP (G) designation. Data per DIN 908 standard / ISO 228-1.

Thread (G)	TPI	Thread Ø (mm)	s — A/F (mm)	e — A/C (mm)	k — Head Height (mm)	t — Socket Depth (mm)	Sealing Ø (mm)
G 1/8	28	9.728	14	16.2	4	3	10
G 1/4	19	13.157	19	21.9	5	4	14
G 3/8	19	16.662	22	25.4	5	4	17
G 1/2	14	20.955	27	31.2	6	5	21
G 5/8	14	22.911	30	34.6	6	5	23
G 3/4	14	26.441	32	36.9	7	6	27
G 7/8	14	30.201	36	41.6	7	6	30
G 1	11	33.249	41	47.3	8	6	33
G 1 1/8	11	37.897	46	53.1	8	6	38
G 1 1/4	11	41.910	50	57.7	9	8	42
G 1 1/2	11	47.803	55	63.5	10	8	48
G 1 3/4	11	53.746	60	69.3	10	8	54
G 2	11	59.614	65	75.1	12	10	60

* s = across flats (A/F); e = across corners (A/C); k = head height; t = minimum socket depth; TPI = threads per inch. All dimensions per DIN 908 / ISO 228-1.

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Allen Key (Hex Key) Size Reference

Thread	G1/8	G1/4	G3/8	G1/2	G3/4	G1	G1¼	G1½	G2
Hex Key (mm)	12	17	19	24	30	36	46	50	60

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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-grade, and mild chemical environments
Magnetic	Slightly magnetic after cold working
Surface Finish	Whitened & Passivated
Temperature Range	−50°C to +300°C (continuous service)

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BSPP (G Thread) — Key Facts

• Thread form: Whitworth 55° parallel thread — constant diameter along thread length
• Standard: ISO 228-1 / BS EN ISO 228 — also known as G thread or BSP parallel
• Does NOT self-seal: Parallel thread requires a bonded seal (Dowty washer) or O-ring face seal for pressure-tight connection
• Common markets: UK, Europe, Asia, Commonwealth — dominant thread in hydraulic and pneumatic systems
• Not interchangeable with BSPT (R thread): Despite similar pitch, BSPP and BSPT are different thread forms and must not be mixed
• Size designation: G1/8, G1/4, G3/8, G1/2 … G2 — the number refers to the nominal bore of the pipe, not the actual thread diameter

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Sealing & Installation Notes

• Thread type: BSPP (G thread) is a parallel thread — it does NOT self-seal. A bonded seal (Dowty washer) or O-ring face seal is mandatory for pressure-tight installation.
• Recommended sealant: Bonded seal (Dowty washer) in stainless-compatible material (e.g. stainless outer ring with NBR or Viton rubber) sized to match thread designation.
• Do NOT use PTFE tape: PTFE tape is designed for tapered threads (BSPT/NPT) and is not effective as a primary sealant for BSPP parallel threads.
• Port compatibility: BSPP (G) plugs fit BSPP-tapped ports only. Do NOT install in BSPT (R thread) tapered ports.
• Galvanic compatibility: A2 stainless is compatible with most stainless steel and aluminium components. Avoid direct contact with carbon steel in wet environments to prevent galvanic corrosion of the carbon steel part.
• Torque: Apply recommended torque per thread size. Do not over-torque — stainless threads can gall (seize) if over-torqued without lubrication.
• Anti-galling: Apply a small amount of anti-seize compound (e.g. copper-based or nickel-based) to threads before installation to prevent galling on stainless-to-stainless connections.
• Re-use: Replace bonded seal on each re-installation.

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Typical Applications

• 🔧 Hydraulic systems — sealing unused BSPP ports on stainless manifolds, cylinders, and valve blocks in corrosive or food-grade environments
• 💨 Pneumatic equipment — closing unused G-thread ports on stainless pneumatic valves and fittings
• 🍼 Food & beverage / pharmaceutical — hygienic port closures in food-grade processing equipment with BSPP ports
• 🌊 Marine & coastal — sealing G-thread ports in marine hydraulic and fluid systems where carbon steel would corrode
• 🧪 Chemical processing — port closures in mild chemical environments where A2 stainless provides adequate resistance
• ⚙️ Machine tools — coolant and lubrication circuit port closures with BSPP ports requiring stainless for hygiene or corrosion resistance

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Frequently Asked Questions

Q: What is the difference between this plug and the carbon steel BSPP version?
A: This plug is manufactured from A2 stainless steel (SUS304) providing significantly better corrosion resistance than carbon steel (black oxide or zinc plated). Choose A2 stainless when the installation environment is corrosive, humid, outdoor, food-grade, or marine-adjacent. Choose carbon steel when cost is the primary consideration and the environment is dry or oil-wetted indoors.

Q: Does BSPP (G thread) self-seal?
A: No. BSPP is a parallel (straight) thread — it does not self-seal through thread interference. A bonded seal (Dowty washer) or O-ring face seal must be used. Do not use PTFE tape as a primary sealant for BSPP connections.

Q: Can stainless steel threads gall (seize)?
A: Yes. Stainless steel is susceptible to galling (cold welding / thread seizure) when stainless threads are torqued against stainless ports without lubrication. Apply a small amount of anti-seize compound (copper-based or nickel-based) to the threads before installation to prevent galling.

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

Q: How do I identify if my port is BSPP or BSPT?
A: Measure the thread diameter at multiple points along the thread length. BSPP threads maintain a constant diameter; BSPT threads taper (reduce in diameter) along the thread length. When in doubt, consult the equipment manufacturer’s documentation or contact FULLERKREG for assistance.