Product
Product Details
Brass Stop Plugs
Brass Stop Plugs
Brass Stop Plugs — also called brass blanking plugs or brass sealing plugs — are threaded closure components used to seal unused cable entry points in electrical enclosures, distribution boards, junction boxes, control panels, and industrial equipment. Manufactured from free-cutting brass to metric thread sizes M16 through M90 and NPT thread sizes 1/4″ through 2″, these plugs provide a reliable, IP-rated seal that prevents ingress of dust, moisture, and gases into protected enclosures. Electrical Accessories India supplies brass stop plugs to OEMs, panel builders, EPC contractors, and distributors worldwide from its manufacturing facility in Jamnagar, Gujarat, India.
Price: US$ 14.50 per kilogram (Ex-works, Jamnagar, India). Custom thread sizes, plating options, and bulk packaging available on request.
Product Overview
What Are Brass Stop Plugs?
A brass stop plug is a solid or semi-solid threaded fastener designed to close off an unused gland entry hole in an electrical enclosure or panel. When cable glands are removed, or when entry holes are pre-drilled but not used, stop plugs seal the opening to maintain the IP rating of the enclosure. They are machined with an external thread matching the cable gland thread — metric or NPT — and typically include a hex or knurled head for tool tightening. Stop plugs are also referred to as blanking plugs, stopping plugs, sealing plugs, knockout plugs, gland blanking inserts, or conduit hole seals depending on the region and industry. They are manufactured to match standard cable gland thread sizes so they are fully interchangeable with glands from all major manufacturers.
Design and Construction
Brass stop plugs are machined from extruded or drawn brass bar stock using CNC turning centers. The body is threaded externally to match the nominal cable gland size, and features a hex head or knurled grip for tightening with a spanner or by hand. A neoprene or EPDM sealing washer is typically fitted under the head to ensure a watertight seal against the enclosure wall. The thread form for metric plugs follows ISO 965-1 with a standard 1.5 mm pitch for sizes M16 to M63 and 2.0 mm pitch for M75 and above. NPT plugs follow ANSI/ASME B1.20.1. The plug body is solid, meaning no cable passes through — this is what distinguishes a stop plug from a cable gland body. Some variants include a nylon or rubber inner seal for enhanced ingress protection. Plugs are available in natural brass finish, nickel-plated, chrome-plated, and hot-dip tinned finishes for different environmental requirements.
Thread Standards and Compatibility
Brass stop plugs manufactured by Electrical Accessories India are compatible with all standard cable gland thread sizes. Metric plugs are threaded to ISO metric coarse thread form and are interchangeable with gland holes tapped to the same standard. NPT plugs follow the American National Taper Pipe Thread standard, providing a pressure-tight seal through thread interference. Plugs can also be supplied to PG (Panzer-Gewinde / DIN 40430) thread sizes for compatibility with German-standard enclosures, and to BSP (British Standard Pipe) thread for UK market applications. All thread forms are machined to tight tolerances ensuring proper fit and IP integrity when installed with the appropriate sealing washer.
Material Grades and Finishes
The standard material for brass stop plugs is free-machining brass CW614N (equivalent to CZ121, CuZn39Pb3, UNS C38500). For applications requiring dezincification resistance — particularly in potable water contact or aggressive industrial environments — DZR brass CW602N is used. Nickel-plated finish provides corrosion resistance for indoor panel applications, while marine-grade plugs may be supplied in stainless steel 316 for offshore and coastal installations. Chrome-plated finish is available for aesthetic panel applications. Hot-dip tinned brass is supplied for EMC-sensitive applications requiring good electrical continuity between plug and enclosure.
Sealing and IP Rating
Brass stop plugs are designed to maintain the IP rating of the enclosure when all entry points are either fitted with a cable gland or sealed with a stop plug. When assembled with the supplied neoprene sealing washer and tightened to the correct torque, metric brass stop plugs achieve IP66, IP67, and IP68 sealing grades as defined in IEC 60529. NPT thread plugs achieve equivalent sealing through the tapered thread interference fit. For IP68 rated applications, additional sealing compound or PTFE thread tape is recommended. The sealing washer must be installed in the correct orientation — against the smooth face of the enclosure — and the plug tightened to the recommended torque (see specifications table) to achieve full IP integrity.
Applications and Industries
Brass stop plugs are used in virtually every sector of electrical and industrial engineering. In panel building and switchgear manufacturing, they seal unused knockout or pre-drilled entry holes in metal enclosures during commissioning and field installation. In the oil and gas industry, they are installed in explosion-proof (Ex d) enclosures to maintain flame-path integrity where cable glands are not fitted. In marine and offshore applications, stainless steel or nickel-plated brass plugs seal junction boxes exposed to salt air and water ingress. In building automation and HVAC, they are used in distribution boards during installation phases. In machine building and OEM equipment, plugs seal any unused entries in motor terminal boxes, control cabinets, and sensor housings. They are also used in the water treatment, food and beverage, and pharmaceutical industries where IP65 or higher enclosure ratings are mandatory.
Comparison with Alternative Sealing Methods
Brass stop plugs are the preferred method for sealing unused cable entries in metal enclosures because they are permanent, reusable, and provide a defined IP rating. Alternative methods such as rubber grommets, plastic snap-in blanks, and adhesive foam pads do not provide the same mechanical strength, temperature resistance, or long-term sealing reliability. Brass plugs withstand temperatures from -40°C to +120°C, resist UV degradation, and maintain their thread integrity over years of service. Unlike plastic blanking plugs, brass plugs do not crack or shrink with age. In explosion-proof (Ex d) enclosures, brass stop plugs (or stainless steel) are required by standard — plastic plugs are not permitted. For IECEx and ATEX certified enclosures, only certified metallic blanking plugs can be used.
Installation and Torque Requirements
Correct installation of brass stop plugs is critical to achieving the required IP rating. The plug should be screwed in by hand initially to verify thread engagement, then tightened with a spanner to the recommended torque. Over-tightening can crack the enclosure wall or damage the thread; under-tightening results in incomplete sealing. For M20 plugs in a 2 mm steel enclosure, a torque of 3–4 Nm is typical. For M63 plugs, 15–20 Nm. The sealing washer should be replaced if the plug is removed and refitted. For NPT plugs, 2–3 turns of PTFE thread tape is recommended on the thread before assembly. Plugs in Ex enclosures must be tightened to the torque specified in the enclosure manufacturer’s installation instructions and must not be loosened without de-energising the circuit.
Key Features
- Metric thread M16 to M90 (1.5 mm pitch) and NPT 1/4″ to 2″ thread forms
- Free-machining brass CW614N / CZ121 construction; DZR brass available
- Natural brass, nickel-plated, chrome-plated, and tinned finish options
- IP66/IP67/IP68 sealing with EPDM/neoprene washer
- ATEX/IECEx compatible for Ex d enclosure sealing
- Compatible with all major cable gland thread patterns
- CNC machined to ISO 965-1 and ANSI/ASME B1.20.1 tolerances
- Available with PG, BSP, metric, and NPT thread forms
- High temperature resistance: -40°C to +120°C
- Bulk packaging for MRO and OEM supply
Thread Form Accuracy
All thread forms are machined on CNC lathes with automatic thread gauging. Go/No-Go gauges verify every production batch. Metric threads comply with ISO 965-1 6g tolerance class. NPT threads are gauged per ANSI/ASME B1.20.1. PG threads comply with DIN 40430. This ensures every plug seats correctly in the tapped entry hole and provides full thread engagement for maximum pull-out strength and seal integrity.
Finish and Corrosion Resistance
Natural brass plugs are suitable for indoor enclosures in non-corrosive environments. Nickel-plated plugs (5–10 µm electroless or electrolytic nickel) provide enhanced corrosion resistance for industrial and outdoor panels. Chrome-plated plugs meet aesthetic requirements for consumer switchgear. Tinned plugs maintain good electrical contact for EMC bonding. For coastal, marine, and offshore environments, stainless steel 316 plugs are recommended. All plating is done in-house at the Jamnagar facility under controlled bath chemistry.
Sealing Washer Options
Standard sealing washers are neoprene (CR) rubber, suitable for -20°C to +90°C service temperature. EPDM washers are available for applications involving ozone, UV, or steam. Silicone washers are used where food-grade or pharmaceutical-grade compliance is required. Viton (FKM) washers are supplied for petrochemical applications involving hydrocarbons, acids, and solvents. Flat copper washers are available for metallic sealing in Ex enclosures. The washer OD matches the plug head diameter to provide full face sealing against the enclosure panel.
ATEX / IECEx Suitability
Brass stop plugs for use in certified Ex d (flameproof) enclosures must be of metallic construction with sufficient thread engagement depth to maintain the flame path. Electrical Accessories India supplies plugs with extended thread engagement length specifically for Ex d applications, complying with IEC 60079-1 and EN 60079-1 requirements for stopping plugs. These plugs are marked with the minimum engagement depth and are supplied with a calibrated sealing washer. For IECEx and ATEX certified enclosures, always verify the enclosure manufacturer’s approved accessories list before substituting plugs.
Dimensional Consistency for OEM Supply
OEM and panel builder customers require plug dimensions to be consistent across production batches to avoid fitment issues during assembly. Electrical Accessories India maintains tight dimensional control with SPC (Statistical Process Control) on all critical dimensions: thread pitch diameter, head across-flats, washer seat diameter, and overall length. CPK values are reviewed monthly and maintained above 1.33 for all critical dimensions. This ensures plug fitment is repeatable across large volume deliveries.
Technical Specifications
| Parameter | Specification |
|---|---|
| Product Name | Brass Stop Plugs / Brass Blanking Plugs |
| Material | Brass CW614N (CZ121, CuZn39Pb3); DZR CW602N optional |
| Thread — Metric | M16, M20, M25, M32, M40, M50, M63, M75, M90 × 1.5 mm pitch (M75/M90 × 2.0 mm) |
| Thread — NPT | 1/4″, 3/8″, 1/2″, 3/4″, 1″, 1¼”, 1½”, 2″ NPT |
| Thread Standard — Metric | ISO 965-1, tolerance class 6g |
| Thread Standard — NPT | ANSI/ASME B1.20.1 |
| Head Type | Hex head (spanner drive); Knurled head (hand tighten) |
| Sealing Washer | Neoprene / EPDM / Silicone / Viton (customer specified) |
| IP Rating (with washer) | IP66, IP67, IP68 (IEC 60529) |
| Temperature Range | -40°C to +120°C (standard); +200°C (Viton/SS variant) |
| Finish Options | Natural Brass, Nickel Plated (5–10 µm), Chrome Plated, Tin Plated, Bare |
| Hardness | 75–90 HRB |
| Tensile Strength | ≥ 390 MPa |
| Price (Brass) | US$ 14.50 per kilogram Ex-works Jamnagar |
| MOQ | 50 kg per size; mixed size orders accepted |
| Lead Time | 2–4 weeks standard; 1 week for repeat orders |
Metric Thread Size Chart — Brass Stop Plugs
| Size | Thread (mm) | Pitch (mm) | Hex A/F (mm) | Body OD (mm) | Length (mm) | Rec. Torque (Nm) | SKU |
|---|---|---|---|---|---|---|---|
| M16 | M16 | 1.5 | 22 | 16.0 | 10 | 2–3 | EAI-BSP-M16 |
| M20 | M20 | 1.5 | 27 | 20.0 | 11 | 3–4 | EAI-BSP-M20 |
| M25 | M25 | 1.5 | 32 | 25.0 | 12 | 4–6 | EAI-BSP-M25 |
| M32 | M32 | 1.5 | 41 | 32.0 | 13 | 6–8 | EAI-BSP-M32 |
| M40 | M40 | 1.5 | 50 | 40.0 | 14 | 8–10 | EAI-BSP-M40 |
| M50 | M50 | 1.5 | 60 | 50.0 | 15 | 10–13 | EAI-BSP-M50 |
| M63 | M63 | 1.5 | 75 | 63.0 | 16 | 13–16 | EAI-BSP-M63 |
| M75 | M75 | 2.0 | 90 | 75.0 | 18 | 16–20 | EAI-BSP-M75 |
| M90 | M90 | 2.0 | 105 | 90.0 | 20 | 20–25 | EAI-BSP-M90 |
NPT Thread Size Chart — Brass Stop Plugs
| NPT Size | OD (in) | TPI | Hex A/F (mm) | Length (mm) | SKU |
|---|---|---|---|---|---|
| 1/4″ NPT | 0.540 | 18 | 16 | 10 | EAI-BSP-NPT14 |
| 3/8″ NPT | 0.675 | 18 | 19 | 11 | EAI-BSP-NPT38 |
| 1/2″ NPT | 0.840 | 14 | 22 | 13 | EAI-BSP-NPT12 |
| 3/4″ NPT | 1.050 | 14 | 27 | 14 | EAI-BSP-NPT34 |
| 1″ NPT | 1.315 | 11.5 | 34 | 16 | EAI-BSP-NPT1 |
| 1¼” NPT | 1.660 | 11.5 | 43 | 18 | EAI-BSP-NPT114 |
| 1½” NPT | 1.900 | 11.5 | 50 | 19 | EAI-BSP-NPT112 |
| 2″ NPT | 2.375 | 11.5 | 60 | 21 | EAI-BSP-NPT2 |
Raw Material Grade Equivalents
| Standard | Grade | Cu % | Zn % | Pb % |
|---|---|---|---|---|
| EN / BS | CW614N / CZ121 | 57–59 | Bal. | 2.5–3.5 |
| EN / BS | CW617N / CZ122 | 56–58 | Bal. | 1.5–2.5 |
| DIN | CuZn39Pb3 | 57–59 | Bal. | 2.5–3.5 |
| UNS (ASTM) | C38500 | 57 | Bal. | 3.0 |
| JIS | C3604 | 59–63 | Bal. | 1.8–3.7 |
| IS (India) | IS 319 Type II | 57–59 | Bal. | 2.5–3.5 |
| DZR Brass | CW602N | 61–63 | Bal. | 0.2–0.5 |
Product Variants
| Variant | Thread | Material | Finish | Washer | IP Rating | Application |
|---|---|---|---|---|---|---|
| Standard Hex Head | Metric / NPT | Brass CW614N | Natural Brass | Neoprene | IP66 | Indoor panels, enclosures |
| Nickel Plated | Metric / NPT | Brass CW614N | Nickel (5–10 µm) | EPDM | IP66/67 | Industrial, outdoor |
| Chrome Plated | Metric | Brass CW614N | Chrome | Neoprene | IP65 | Consumer switchgear |
| Knurled Head | Metric | Brass CW614N | Natural / Nickel | EPDM | IP65 | Hand-tighten applications |
| Ex d Grade | Metric / NPT | Brass CW614N | Nickel Plated | Viton | IP66/68 | ATEX / IECEx Ex d enclosures |
| DZR Brass | Metric / NPT | Brass CW602N | Natural / Nickel | EPDM | IP67 | Potable water, corrosive envir. |
| Stainless Steel 316 | Metric / NPT | SS 316 | Passivated | Silicone | IP68 | Marine, offshore, food grade |
| Large Size M75–M90 | M75 / M90 | Brass CW614N | Natural / Nickel | EPDM | IP66 | Large cable entry sealing |
Applications in Industry
| Industry | Application | Typical Size | Finish Required |
|---|---|---|---|
| Panel Building / Switchgear | Sealing unused gland entries in MCC, MDB, SDB panels | M20, M25, M32 | Nickel Plated |
| Oil & Gas — Onshore | Ex d flameproof junction box sealing | M20, M25, M32, M40 | Nickel Plated / Brass |
| Oil & Gas — Offshore | Marine grade enclosure sealing, IP68 | M20–M63 | SS 316 / Nickel |
| Power Utilities | Transformer terminal box, switchgear enclosures | M32, M40, M50 | Brass / Nickel |
| Marine & Shipbuilding | Deck junction boxes, engine room panels | M20–M50 | SS 316 |
| Building Automation | BMS panels, fire alarm control panels | M16, M20, M25 | Nickel / Chrome |
| Machine Building / OEM | Motor terminal boxes, control cabinets | M20, M25, M32 | Natural Brass / Nickel |
| Water Treatment | IP65/IP66 enclosures in wet environments | M20, M25 | DZR / Nickel |
| Food & Beverage | Stainless panels in wash-down zones | M20, M25 | SS 316 / Silicone |
| Renewable Energy | Solar inverter combiner boxes, wind turbine panels | M20, M25, M32 | Nickel Plated |
Manufacturing Process
- Material Procurement: Extruded brass bar CW614N or drawn hex bar procured from certified Indian brass mills. Material certificates (EN 10204 3.1 or 2.2) supplied on request.
- CNC Bar Turning: Plugs are machined on multi-spindle CNC lathes. OD, thread, and hex features are machined in one setup for concentricity and positional accuracy.
- Thread Cutting / Rolling: Threads are cut or rolled on the same CNC turning center. Thread rolling is preferred for stronger thread roots and better surface finish.
- Thread Gauging: Every part is gauged with Go/No-Go thread gauges. For metric threads: ISO 965-1 6g; for NPT: ANSI/ASME B1.20.1.
- Deburring and Washing: Parts are tumble-deburred to remove machining burrs, then ultrasonically cleaned and phosphate degreased before plating.
- Plating: Nickel plating (electroless or electrolytic), chrome plating, or tin plating applied in in-house plating baths. Plating thickness verified by XRF.
- Washer Assembly: Neoprene/EPDM/Viton washers fitted to each plug. Washer OD, ID, and thickness verified per drawing.
- Final Inspection: Dimensional check (OD, length, hex A/F, thread), visual inspection for surface defects, plating adhesion check per ASTM B571.
- Packing: Packed in polybag + box by size and SKU. Boxes labeled with size, material, finish, quantity, and batch number. Pallet packing for bulk orders.
Quality Standards and Certifications
| Standard / Certification | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — manufacturing and inspection |
| IEC 60529 | IP rating standard — sealing performance classification |
| BS 6121 / BS EN 62444 | Cable gland standards applicable to accessories |
| ISO 965-1 | Metric thread tolerance standard (6g for external threads) |
| ANSI/ASME B1.20.1 | NPT pipe thread standard |
| IEC 60079-1 / EN 60079-1 | Ex d flameproof enclosure requirements (stopping plugs) |
| REACH / RoHS | Hazardous substance compliance for EU export |
| EN 10204 3.1 | Material test certificate available on request |
Why Choose Electrical Accessories India
- Manufacturer with 25+ years in precision brass machined components for electrical OEMs
- Complete range of cable gland accessories: Brass Lock Nuts, Stainless Steel Lock Nuts, PVC Shrouds for Cable Glands, Earth Tags, Thread Reducers and Adapters
- Full range of Cable Glands including Brass CW Cable Glands, Brass BW Cable Glands, Brass CET Glands, Stainless Steel Cable Glands
- CNC machining capacity: 200+ lathes, multi-spindle and CNC turning centers
- In-house plating: nickel, chrome, tin, silver
- Thread gauging on 100% of production
- Material traceability: heat number to finished part
- Export to 40+ countries; established agent network in UK, Germany, UAE, USA, Australia
- Custom thread forms, sizes, and packaging available on request
Frequently Asked Questions
What is a brass stop plug used for?
A brass stop plug seals unused cable entry holes in electrical enclosures, panels, and junction boxes. It maintains the IP rating of the enclosure and prevents ingress of dust, water, and gases through open gland entries.
What thread sizes are available for brass stop plugs?
Electrical Accessories India supplies brass stop plugs in metric sizes M16, M20, M25, M32, M40, M50, M63, M75, and M90 (1.5 mm pitch), and in NPT sizes from 1/4″ to 2″. PG and BSP threads are available on request.
What is the difference between a stop plug and a blanking plug?
Stop plug and blanking plug are two names for the same product — a solid threaded fastener used to seal unused cable entries. The term “stop plug” is more common in UK/European markets; “blanking plug” is used interchangeably. Both terms refer to the same component.
Can brass stop plugs be used in ATEX/IECEx Ex d enclosures?
Yes. Brass stop plugs with sufficient thread engagement depth and metallic construction are suitable for use in Ex d (flameproof) enclosures. Always verify that the plug is approved for the specific enclosure certification and tightened to the torque specified by the enclosure manufacturer.
What IP rating do brass stop plugs achieve?
With the supplied neoprene or EPDM sealing washer correctly installed and tightened to the recommended torque, brass stop plugs achieve IP66 and IP67 as defined in IEC 60529. IP68 can be achieved with Viton washer and thread sealant. NPT plugs achieve equivalent sealing through thread interference.
Are brass stop plugs compatible with all cable gland brands?
Yes. Brass stop plugs are threaded to standard metric ISO or NPT thread forms, making them compatible with gland holes from all major manufacturers including Hawke, Roxtec, Wiska, Jacob, and CMP, provided the thread form and size match.
What material is used for brass stop plugs?
Standard material is free-machining brass CW614N (equivalent to CZ121 per BS EN 12164, and UNS C38500). DZR brass CW602N is available for dezincification-resistant applications. Stainless steel 316 is available for marine and offshore use.
What is the price of brass stop plugs?
Brass stop plugs are priced at US$ 14.50 per kilogram ex-works Jamnagar, India. Pricing is subject to copper LME fluctuation. Nickel-plated variants carry a surface treatment premium. Contact us for exact pricing based on size, quantity, and finish.
Do brass stop plugs come with sealing washers?
Yes. All brass stop plugs are supplied with a neoprene sealing washer as standard. EPDM, Silicone, and Viton washer options are available. The washer is pre-fitted on the plug for ease of installation.
What is the minimum order quantity for brass stop plugs?
The standard minimum order quantity is 50 kg per size. Mixed size orders are accepted with a minimum of 10 kg per size. Sample quantities of 1–5 kg are available for evaluation at cost-plus pricing.
Equivalent Terms in Other Languages
| Language | Term 1 | Term 2 | Term 3 |
|---|---|---|---|
| Spanish | Tapón de latón | Tapón ciego de latón | Tapón de sellado de latón |
| French | Bouchon obturateur en laiton | Bouchon borgne en laiton | Bouchon d’obturation en laiton |
| Russian | Латунная заглушка | Латунная глухая пробка | Латунный уплотнительный штуцер |
| Portuguese | Tampa de latão para prensa-cabo | Plug cego de latão | Tampão de latão |
| Italian | Tappo cieco in ottone | Tappo di chiusura in ottone | Tappo passacavo in ottone |
Related Products
- Brass Lock Nuts — Metric M16–M90 and NPT lock nuts for cable gland securing
- Stainless Steel Lock Nuts — SS 316 lock nuts for marine and corrosive environments
- PVC Shrouds for Cable Glands — Weatherproof shrouds for outdoor cable gland protection
- Earth Tags Brass — Earthing continuity tags for cable gland assemblies
- Thread Reducers and Adapters — Metric and NPT thread reducers for gland size adaptation
- Brass CW Cable Glands — Standard brass cable glands for armoured cable
- Brass BW Cable Glands — Brass glands for unarmoured cable
- Brass CET Glands — Central Earth Termination cable glands
- Stainless Steel Cable Glands — SS 316 glands for harsh environments
- Marine Cable Glands — Marine grade glands for shipboard use
- Aluminium Cable Glands — Lightweight aluminium glands for zone 1 hazardous areas
Request a Quote
To receive a quotation for brass stop plugs, please provide: thread type (metric/NPT), size range, quantity (kg or pieces per size), finish required, and delivery destination. Our team will respond within 24 hours on business days.
Email: sales@elecaccs.com
Phone/WhatsApp: +91-98765-XXXXX
Contact Form: Contact Electrical Accessories India