Home » Imperial BSPT Socket Pipe Plugs (DIN 906) - Marine Stainless Steel (A4)

Imperial BSPT Socket Pipe Plugs (DIN 906) - Marine Stainless Steel (A4)

Imperial BSPT Socket Pipe Plugs - DIN 906 | Marine Stainless Steel A4 (SUS316) | A4-70 | Pickled & Passivated

FULLERKREG DIN 906 imperial BSPT (British Standard Pipe Taper) hexagon socket screw plugs in A4 marine-grade stainless steel (SUS316 / EN 1.4401), A4-70 strength grade, pickled & passivated surface finish. The premium choice for self-sealing port closures in saltwater, chemical, and aggressive industrial environments. BSPT (R thread, ISO 7-1) tapered thread creates a self-sealing interference fit on tightening. Internal hexagon socket drive allows flush or recessed installation where external wrench access is restricted.

Product Overview

  • Standard: DIN 906 (Tapered Hexagon Socket Screw Plugs)
  • Thread Standard: BSPT - British Standard Pipe Taper (ISO 7-1 / R Thread)
  • Thread Type: Tapered pipe thread - self-sealing by thread interference
  • Material: A4 Marine Stainless Steel (SUS316 / EN 1.4401)
  • Strength Grade: A4-70 (ISO 3506-1)
  • Surface Treatment: Pickled & Passivated
  • Drive: Internal hexagon socket (Allen / hex key)
  • Size Range: R 1/8 to R 2
  • Brand: FULLERKREG

Dimensions - DIN 906 BSPT / R Thread (Marine Stainless Steel)

All dimensions in mm. Per DIN 906 standard for BSPT plugs. h = plug height, k = socket depth. Weight in kg/100pcs.

Thread (R) TPI Thread OD (mm) h (mm) k (mm) S/AF (mm) Weight (kg/100pcs)
R 1/8 28 9.728 6 3 4 2
R 1/4 19 13.157 8 5 5 4
R 3/8 19 16.662 10 6 6 7
R 1/2 14 20.955 10 7 8 9
R 3/4 14 26.441 10 8 10 18
R 1 11 33.249 12 10 12 35
R 1-1/4 11 41.910 12 10 14 39
R 1-1/2 11 47.803 12 12 17 63
R 2 11 59.614 15 12 19 39

S/AF = internal hex socket size (Allen key size). Thread OD per ISO 7-1. Dimensions per DIN 906 standard for BSPT plugs.

BSPT Thread Reference (ISO 7-1 / R Thread)

Thread (R) TPI Pitch (mm) Major Dia. (mm) Taper
R 1/8 28 0.907 9.728 1:16
R 1/4 19 1.337 13.157 1:16
R 3/8 19 1.337 16.662 1:16
R 1/2 14 1.814 20.955 1:16
R 3/4 14 1.814 26.441 1:16
R 1 11 2.309 33.249 1:16
R 1-1/4 11 2.309 41.910 1:16
R 1-1/2 11 2.309 47.803 1:16
R 2 11 2.309 59.614 1:16

Material & Mechanical Properties

  • Material: A4 / AISI 316 / SUS316 / EN 1.4401 - Austenitic stainless steel with molybdenum
  • Molybdenum Content: 2-3% Mo - key differentiator providing superior pitting and crevice corrosion resistance vs A2
  • Strength Class: A4-70 per ISO 3506-1
  • Tensile Strength: 700 N/mm2 min (101,500 PSI)
  • Proof Load Stress: 450 N/mm2 min
  • Hardness: HV 220 max
  • Surface: Pickled & Passivated - removes free iron, maximises chromium oxide passive layer
  • Generally non-magnetic in annealed condition

Surface Treatment: Pickled & Passivated

  • Pickling: Acid treatment removes heat tint, scale, and free iron contamination from manufacturing
  • Passivation: Rebuilds dense chromium oxide (Cr2O3) passive film for maximum corrosion protection
  • Result: Bright silver-white surface with maximum corrosion resistance
  • No dimensional change - thread tolerances fully maintained
  • Per ASTM A967 / ISO 16048 passivation requirements

Key Features

  • Marine-grade corrosion resistance: 2-3% molybdenum in SUS316 dramatically improves resistance to chloride pitting - essential for saltwater, coastal, and offshore environments
  • Self-sealing BSPT tapered thread: 1:16 taper creates interference seal on tightening - no sealing washer required in most applications
  • Internal hex socket drive: Allen key installation allows flush or below-surface fitting - ideal where external wrench access is restricted
  • Compact low-profile design: Minimal protrusion above mating surface
  • A4-70 strength: High strength combined with maximum corrosion resistance for demanding environments
  • Chemical resistance: Resistant to many acids, alkalis, chlorides, and industrial chemicals
  • Wide size range: R 1/8 to R 2 from stock

A4 (SUS316) vs A2 (SUS304) - Why Choose Marine Grade?

Property A2 (SUS304) A4 (SUS316) - This Product
Base Alloy 18% Cr, 8% Ni 16% Cr, 10% Ni, 2-3% Mo
Molybdenum None 2-3% (pitting resistance)
Saltwater Resistance Moderate Excellent
Chloride Resistance Limited Superior
Chemical Resistance Good Very Good
Strength Grade A2-70 A4-70
Best For General industrial Marine, chemical, harsh environments

BSPT vs BSPP - Know the Difference

Property BSPT (This Product) BSPP (Parallel)
Thread Form Tapered (1:16) Parallel (cylindrical)
Standard ISO 7-1 / R thread ISO 228-1 / G thread
Sealing Method Thread interference - self-sealing Face seal (collar + washer/O-ring)
Sealing Washer Not required Required for pressure sealing
Reusability Limited - taper deforms slightly Excellent - no thread deformation
Interchangeable? No - do not mix BSPT and BSPP threads

Typical Applications

  • Marine and offshore equipment - hull fittings, seawater systems with BSPT ports
  • Shipbuilding and boat manufacturing
  • Coastal and harbour infrastructure
  • Chemical and petrochemical processing pipelines
  • Pharmaceutical and food processing (CIP systems)
  • Hydraulic manifold and cylinder port closures (BSPT-threaded)
  • Desalination plants and water treatment facilities
  • Swimming pool and spa equipment
  • Machine tool coolant systems with aggressive coolants
  • OEM production line fastener supply

Standards & Compliance

  • DIN 906 - Tapered Hexagon Socket Screw Plugs
  • ISO 7-1 - Pipe threads where pressure-tight joints are made on the threads (BSPT / R thread)
  • BS 21 - British Standard for taper pipe threads
  • ISO 3506-1 - Mechanical properties of corrosion-resistant stainless steel fasteners
  • ASTM A967 / ISO 16048 - Passivation of stainless steel
  • RoHS / REACH - Compliant
  • Mill Test Certificates (EN 10204 3.1) available on request

Ordering & Packaging

  • Standard bulk packaging: per 100 pcs or per 1000 pcs
  • Custom quantities for OEM and production orders
  • Labelled with thread size (R), material grade (A4-70), surface treatment, and DIN 906
  • Most sizes available from stock - fast dispatch
  • MTC / EN 10204 3.1 certificates available on request

FAQ

Q: What makes A4 better than A2 for marine applications?
A: A4 (SUS316) contains 2-3% molybdenum which dramatically improves resistance to chloride pitting and crevice corrosion - the primary failure mode in saltwater environments. A2 (SUS304) lacks molybdenum and is not recommended for prolonged saltwater exposure.

Q: What is BSPT thread and how does it differ from BSPP?
A: BSPT (R thread per ISO 7-1) is a tapered thread that seals by thread interference - no washer needed. BSPP (G thread per ISO 228-1) is parallel and requires a face seal washer. They use the same 55 degree Whitworth thread form but are not interchangeable.

Q: Does a BSPT plug need PTFE tape or thread sealant?
A: For low-pressure applications, the taper interference alone is often sufficient. For higher pressure or critical sealing, PTFE tape or anaerobic thread sealant is recommended as additional insurance.

Q: What Allen key size do I need?
A: The internal hex socket size (S/AF) varies by thread size - see the dimensions table above. For example, R 1/2 uses an 8mm hex key, R 1 uses a 12mm hex key.

Q: Are Mill Test Certificates available?
A: Yes. FULLERKREG provides EN 10204 3.1 material certificates for all A4 stainless steel fasteners upon request.

Q: Is A4 stainless suitable for high-temperature applications?
A: A4 (SUS316) performs well up to approximately 870 degrees C in intermittent service. For sustained high-temperature applications above 300 degrees C, please consult our technical team.

All FULLERKREG DIN 906 BSPT marine stainless steel socket pipe plugs are manufactured to DIN and ISO standards. Contact FULLERKREG for bulk pricing, OEM supply, or technical support.

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