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Brass Thread Adapters and Enlargers
Brass Thread Adapters and Enlargers
Brass Thread Adapters and Enlargers are precision-machined conduit fittings used to adapt, increase, or step up thread sizes at cable entry points of electrical enclosures, panel boards, junction boxes, motor terminal boxes, switchgear, and industrial control panels. Unlike reducer bushes that step down a thread, thread enlargers provide a larger internal (female) thread within a smaller external (male) thread body, enabling installation of larger-diameter cable glands, conduit fittings, or conduit locknuts into an existing enclosure entry. Available in Metric-to-Metric (ISO 965-1, 1.5 mm pitch) and NPT × Metric / Metric × NPT cross-configurations, these adapters are manufactured by Electrical Accessories India, Jamnagar, Gujarat, India—one of the world’s leading brass machined parts manufacturing centres.
Indicative Pricing
Brass Items: US$ 11.50 per kilogram, CIF US Port / Major Indian Port. Price varies by size, combination, surface treatment, and order quantity. Contact us with your RFQ for a firm quotation.
Product Overview
What Are Brass Thread Adapters and Enlargers?
A brass thread adapter (also called a conduit thread enlarger, cable entry adapter, thread step-up bush, entry adaptor, thread extension fitting, or conduit enlarging bush) is a machined brass fitting with a male thread of a smaller size and a female thread of a larger size. It threads into the conduit entry from outside (or inside) and allows installation of a cable gland, conduit connector, or PG fitting of a larger nominal size than the original enclosure knockout. This is common in retrofit or upgrade scenarios where existing enclosures need to accommodate larger cables, or where a standard enclosure with a smaller knockout must accept a conduit system of a larger size. Electrical Accessories India manufactures standard and custom thread adapter and enlarger combinations in metric and NPT configurations.
Thread Adapter vs. Thread Reducer – Engineering Distinction
A thread reducer bush reduces (steps down) the internal thread size—external thread is larger, internal thread is smaller. A thread enlarger or adapter increases (steps up) the entry size—the fitting is threaded into a smaller hole and presents a larger internal thread to accept a larger fitting. In practice, the terms “adapter”, “enlarger”, “step-up bush”, “entry adaptor”, and “reducing bush” are sometimes used interchangeably in the industry, but the distinction is: does the fitting increase or decrease the effective entry size? Thread adapters are used in both directions: adapting NPT-threaded NEMA enclosures to metric conduit systems, or adapting metric enclosures to accept NPT fittings used in American specifications.
Metric to Metric Thread Adapters
Metric-to-metric thread adapters are available in combinations stepping up or down across the standard metric conduit entry size series: M16×1.5, M20×1.5, M32×1.5, M40×1.5, M50×1.5, M63×1.5, and M75×1.5. Common enlarger combinations include: M16 male × M20 female, M20 male × M32 female, M32 male × M40 female, M40 male × M50 female. Common reducer combinations include: M20 male × M16 female, M32 male × M20 female, M40 male × M32 female, M50 male × M40 female, M63 male × M50 female, M75 male × M63 female. All threads conform to ISO 965-1 fine metric thread, 1.5 mm pitch, tolerance class 6H/6g, ensuring global interchangeability with European DIN, British BS, and IEC 62444 standard cable gland and conduit fitting dimensions.
NPT × Metric and Metric × NPT Thread Adapters
NPT × Metric adapters convert between American National Pipe Thread Tapered (ANSI/ASME B1.20.1) and ISO metric thread standards. The most common configurations are: ½” NPT male × M20 female, ¾” NPT male × M25 female, 1″ NPT male × M32 female, 1¼” NPT male × M40 female, 1½” NPT male × M50 female, and 2″ NPT male × M63 female. The reverse—Metric × NPT adapters—allow metric enclosures to accept NPT-threaded cable glands and conduit fittings used in American, Canadian (CSA C22.2), and Middle Eastern project specifications. This cross-standard compatibility is particularly important in petrochemical, LNG, power generation, and offshore projects using mixed American and European electrical equipment and cable gland standards.
Material and Alloy Grades
Standard manufacturing material is free-cutting brass IS 319 Type I, equivalent to CuZn39Pb3 / CW614N (EN 12164), BS 2874 CZ121, ASTM B16 UNS C36000. For coastal, marine, chemical, and offshore environments, dezincification-resistant (DZR) brass CuZn35Pb2Al / CW602N / BS 2874 CZ132 is offered. For high-corrosion or high-hygiene applications (food processing, pharmaceutical), electroless nickel-plated (ENP) or stainless steel (SS 316L) versions are available. Brass provides the optimal combination of machinability, electrical conductivity, mechanical strength, and corrosion resistance for conduit fitting applications across temperature ranges of -40°C to +120°C.
Body Design and Sealing
Brass thread adapters are turned with a hexagonal or round flange providing a mechanical stop against the enclosure wall or knockout edge. The flange design ensures tool-tightened installation without pull-through. A neoprene or EPDM flat washer or O-ring (optional) between flange and enclosure face achieves IP54 to IP67 sealing when combined with a locknut on the opposite side. Extended body versions accommodate thicker enclosure walls (3–6 mm) or gland plates (3–5 mm thick). The internal female thread accepts standard cable glands conforming to BS EN 50262 / IEC 62444 / IS 12943, including armoured cable glands (SWA/AWA type), unarmoured types, EMC shielded types, and Ex-certified glands for hazardous area use.
NPT-to-Metric Cross Compatibility for International Projects
International engineering projects—particularly in the Middle East, North Africa, Southeast Asia, and Africa—frequently involve enclosures with NPT entry threads (specified to NEMA, UL, or IEC standards for North American export) that must accept metric cable glands or conduit (specified to BS, IEC, or DIN standards preferred locally). Brass thread adapters with ¾” NPT male × M20 female, or 1″ NPT male × M32 female, are the most widely ordered configuration for this cross-standard challenge. Conversely, European or Asian-manufactured enclosures with M20 or M25 metric entries are adapted to accept ½” or ¾” NPT cable glands for projects using American material takeoffs. Both directions of adaptation are available from stock.
Corrosion Protection and Surface Treatments
Standard finish is natural bright machined brass. Optional finishes include: electroless nickel plating (ENP, 25–50 µm) for marine and chemical resistance; hot-dip tin plating for enhanced solderability and corrosion protection; black oxide for aesthetic and mild corrosion protection; electrolytic zinc-nickel alloy plating for automotive and outdoor applications. All plating processes comply with RoHS 2011/65/EU. Salt-fog resistance testing per IEC 60068-2-52 and ASTM B117 is available on request. UV-stabilised surfaces for outdoor installations can also be arranged through specialised coating processes.
Key Features
- Metric × Metric (M16–M75, all 1.5 mm pitch) and NPT × Metric / Metric × NPT configurations
- Material: Brass IS 319 / CuZn39Pb3 / CW614N; DZR brass available for marine/chemical use
- Complies with ISO 965-1 (metric thread) and ANSI/ASME B1.20.1 (NPT thread)
- Hexagonal or round flanged design for spanner-tightened installation
- Compatible with IEC 62444 / BS EN 50262 / IS 12943 cable glands
- Optional sealing washer (neoprene/EPDM) for IP66/IP67 assembly
- ATEX / IECEx compatible versions for hazardous area installations
- RoHS and REACH compliant; MSDS and MTR certificates available
- Custom thread combinations and non-standard sizes on request
- Applications in power, oil and gas, marine, renewables, railways, and defence
Flanged Entry Design for Enclosure Integrity
The flanged design of the thread adapter ensures a secure mechanical stop against the enclosure wall preventing push-through under cable pull force. The flange OD is sized to adequately overlap the knockout edge for all standard enclosure cutout tolerances. Knurling or serrations on the flange underface resist rotation caused by torque transmitted through cable gland tightening. For thin-wall enclosures (1–2 mm sheet metal), the flat face of the flange distributes clamping load to avoid deformation of the panel wall. Spanner A/F dimensions follow standard metric spanner sizing (typically 27 mm A/F for M20, 36 mm A/F for M32, etc.).
Electrical Continuity and Earthing
When installed in metallic conduit systems or with earthed metal cable glands, brass thread adapters maintain full electrical continuity of the conduit earth and cable screen bonding path. This supports compliance with IEC 60364-5-54 (earthing and bonding), NEC Article 250, and AS/NZS 3000 for equipotential bonding in electrical installations. The metallic path through the adapter and locknut assembly provides a low-impedance earth return path, critical for fault protection and EMC shielding performance in industrial and commercial installations.
Wide Range of Thread Combinations for OEM Use
For OEM panel builders, machine builders, and enclosure manufacturers, Electrical Accessories India offers thread adapters with part numbering, laser engraving, colour-coded anodising, and custom packaging. Common OEM combinations include: M20 × M16 (for European panels), ¾” NPT × M20 (for petrochemical export), M32 × M25 (for mid-size cable entries), M40 × M32 (for larger cable routes). Small batch samples are available for fitment testing before series production commitment.
ATEX/IECEx Application Support
For hazardous area zone 1 and zone 2 installations per ATEX Directive 2014/34/EU and IECEx System, thread adapters are supplied with tight dimensional tolerances and material certifications to support certified Ex-e and Ex-d cable gland assemblies. Batch-level material test reports (MTR), RoHS/REACH declarations, and dimensional certificates are provided. Third-party inspection by Lloyd’s Register, DNV GL, SGS, Intertek, or Bureau Veritas can be arranged for export orders to the Middle East, Europe, and offshore projects.
Compatibility with International Enclosure Standards
Brass thread adapters from Electrical Accessories India are compatible with enclosures conforming to IEC 60439, IEC 61439, NEMA 250, UL 508A, BS EN 60439, IP54 to IP67 (IEC 60529), GOST R (Russia), and SASO (Saudi Arabia). They accommodate enclosure wall thicknesses from 1.5 mm to 6 mm through standard and extended body versions. Compatibility with flange plates (sub-plates), gland plates, and modular cable entry systems is also supported through custom sizing.
Technical Specifications
| Parameter | Specification |
|---|---|
| Material (Standard) | Free-Cutting Brass IS 319 / CuZn39Pb3 / CW614N |
| Material (DZR Option) | DZR Brass CuZn35Pb2Al / CW602N / BS 2874 CZ132 |
| Thread Standard (Metric) | ISO 965-1, Pitch 1.5 mm, Tolerance Class 6H/6g |
| Thread Standard (NPT) | ANSI/ASME B1.20.1 Tapered Pipe Thread |
| Metric Thread Range | M16×1.5, M20×1.5, M32×1.5, M40×1.5, M50×1.5, M63×1.5, M75×1.5 |
| NPT Thread Range | ½” NPT, ¾” NPT, 1″ NPT, 1¼” NPT, 1½” NPT, 2″ NPT |
| Surface Finish (Standard) | Natural bright machined brass |
| Surface Finish (Options) | Electroless Nickel Plating (ENP), Tin Plating, Black Oxide, Zinc-Nickel |
| Sealing Provision | Neoprene / EPDM flat washer or O-ring (optional) |
| IP Rating (with locknut + washer) | Up to IP66 / IP67 |
| Operating Temperature | -40°C to +120°C |
| Hardness (Brass) | 80–120 HV |
| Tensile Strength | 380–420 MPa |
| Country of Origin | Jamnagar, Gujarat, India |
| RoHS Compliance | Yes – RoHS 2011/65/EU |
International Material Equivalent Table
| Standard | Designation | Description |
|---|---|---|
| Indian IS 319 | IS 319 Type I | Free-cutting brass bar |
| European EN 12164 | CuZn39Pb3 / CW614N | Free-machining brass rod |
| British BS 2874 | CZ121 | Leaded brass rod |
| American ASTM B16 | UNS C36000 | Free-cutting brass |
| German DIN 17660 | CuZn39Pb3 | Brass machining rod |
| Japanese JIS H3250 | C3604 | Free-cutting brass rod |
| DZR (EN) | CuZn35Pb2Al / CW602N | DZR brass rod |
Thread Adapter Size Matrix (Common Combinations)
| Adapter Type | External (Male) Thread | Internal (Female) Thread | Application |
|---|---|---|---|
| Metric Enlarger | M16×1.5 | M20×1.5 | Step-up for cable gland upgrade |
| Metric Enlarger | M20×1.5 | M32×1.5 | Retrofit to larger cable gland |
| Metric Reducer | M20×1.5 | M16×1.5 | Reduce entry for smaller gland |
| Metric Reducer | M32×1.5 | M20×1.5 | Standard reducer |
| Metric Reducer | M40×1.5 | M32×1.5 | Standard reducer |
| Metric Reducer | M50×1.5 | M40×1.5 | Standard reducer |
| Metric Reducer | M63×1.5 | M50×1.5 | Standard reducer |
| NPT × Metric | ½” NPT | M20×1.5 | NEMA enclosure to metric gland |
| NPT × Metric | ¾” NPT | M25×1.5 / M32×1.5 | NEMA to metric adaptation |
| NPT × Metric | 1″ NPT | M32×1.5 / M40×1.5 | Petrochemical cross-standard |
| Metric × NPT | M20×1.5 | ½” NPT | Metric enclosure to NPT gland |
| Metric × NPT | M32×1.5 | ¾” NPT | Metric to American standard |
Product Types and Variants
-
- Type A – Metric × Metric Enlarger Bush: Step-up adapter; smaller male thread, larger internal female thread. For upgrading existing enclosure entry to larger cable gland.
- Type B – Metric × Metric Reducer Bush: Step-down adapter; larger male thread, smaller internal female thread. Standard reducer for cable entry size reduction.
- Type C – NPT × Metric Adapter: External NPT tapered male thread, internal ISO metric female thread. For NEMA / UL enclosures accepting metric cable glands.
- Type D – Metric × NPT Adapter: External ISO metric male thread, internal NPT tapered female thread. For metric enclosures accepting American NPT cable glands.
- Type E – DZR Brass Thread Adapter: All above types in dezincification-resistant brass for offshore, marine, and chemical installations.
Type F – Nickel-Plated Thread Adapter:
- ENP-coated for coastal, humid, or corrosive atmosphere installations.
Applications in Industry
- Power Generation and Utilities: Generator terminal boxes, transformer marshalling boxes, substation control panels, SCADA panels requiring mixed thread standards
- Oil and Gas / Petrochemical: Hazardous area Ex-d / Ex-e junction boxes requiring NPT × Metric or Metric × NPT adaptation for mixed international equipment
- Marine and Offshore: Ship engine room panel wiring, offshore platform junction boxes, subsea topside panel adapters
- Renewable Energy: Wind turbine nacelle junction boxes with mixed European/American component supply, solar PV string combiner boxes, EV charging station assemblies
- Defence and Rail: Military vehicle panel wiring, railcar junction boxes, locomotive control cubicles with international supply specifications
- Building Services / Infra: Airport, metro, hospital, and data centre panels requiring cross-standard cable gland adaptation
- Panel Builders and OEMs: MCC panels, PLC control cabinets, VFD enclosures, motor starters, and custom switchgear requiring non-standard cable entries
Manufacturing Process
Brass thread adapters and enlargers are manufactured on CNC multi-spindle automatic lathes (Swiss-type or Davenport-type) from precision brass bar stock (IS 319 / CW614N). The sequence is: (1) bar feeding and stock positioning, (2) external profile rough and finish turning, (3) hexagonal or round flange forming (milling or forming), (4) drilling and counterboring of internal bore, (5) external thread cutting by die head or single-point CNC threading (metric or NPT), (6) internal thread cutting by tapping head or thread milling for metric; by NPT pipe tap for tapered thread, (7) parting off and chamfering, (8) ultrasonic deburring and cleaning, (9) thread gauging with Go/No-Go gauges to ISO 965-1 and ANSI B1.20.1, (10) dimensional verification with CMM, (11) surface treatment (ENP, tin, or black oxide if specified), (12) final inspection, tagging, and packing. Production capacity: 30,000–50,000 pieces/day on standard sizes. Custom combinations available with 2–4 week lead time.
Quality Standards and Certifications
- ISO 9001:2015 Quality Management System certified manufacturing facility
- Thread gauging per ISO 965-1 (metric) and ANSI B1.20.1 (NPT)
- Dimensional inspection by CMM and optical comparator
- RoHS 2011/65/EU compliance; REACH SVHC declarations on request
- Salt-spray testing per IEC 60068-2-52 and ASTM B117
- Cable gland compatibility: IEC 62444 / BS EN 50262 / IS 12943
- ATEX/IECEx component specifications available for Ex-certified assembly
- Marine classification: Lloyd’s Register, DNV GL, Bureau Veritas approvals available
- Material Test Reports (MTR) and Certificate of Conformity (COC) standard with shipment
Why Choose Electrical Accessories India
- Comprehensive Thread Range: Full matrix of metric (M16–M75) and NPT (½”–2″) thread adapter combinations—more combinations in stock than most competitors.
- Jamnagar Manufacturing Precision: Automated CNC turning, thread gauging, and quality systems ensure dimensional consistency across large orders.
- Cross-Standard Expertise: Deep knowledge of ISO, DIN, BS, ANSI, and IEC thread standards for conduit and cable gland applications.
- Export Documentation: Commercial invoice, packing list, COO, MSDS, MTR, and inspection certificates provided for all export orders.
- Custom OEM Supply: Part marking, custom packaging, special alloys, and non-standard thread combinations available.
- Competitive Pricing: Jamnagar-based manufacturing with direct export pricing: US$ 11.50/kg for brass—highly competitive globally.
Frequently Asked Questions (FAQ)
Q1: What is the difference between a thread adapter and a thread reducer?
A thread reducer bush steps down the internal thread size (external larger, internal smaller). A thread adapter can refer to either step-up (enlarger) or step-down (reducer) or a cross-standard adapter (Metric to NPT or vice versa). The term is often used generically for any fitting that adapts between two different thread types or sizes.
Q2: What thread adapter do I need to fit a metric cable gland into a ¾” NPT enclosure knockout?
You need a ¾” NPT male × M25 or M32 female adapter. This threads into the ¾” NPT knockout of your NEMA enclosure and presents an M25 or M32 metric female thread to accept the metric cable gland. Contact us specifying the gland manufacturer and model for a precise recommendation.
Q3: Are metric thread adapters available with all 1.5 mm pitch?
Yes. All standard metric conduit thread adapters are manufactured with 1.5 mm pitch per ISO 965-1. Sizes available: M16, M20, M32, M40, M50, M63, and M75. M25 and M63 are also available on request.
Q4: What is the price for brass thread adapters and enlargers?
Price: US$ 11.50 per kilogram, CIF US Port or Major Indian Port. DZR brass, nickel-plated, and stainless steel versions are quoted separately. Volume pricing available for orders above 500 kg/month.
Q5: Can I use a metric × NPT adapter to fit a ½” NPT cable gland into an M20 enclosure entry?
Yes. An M20×1.5 male × ½” NPT female adapter fits into the M20 enclosure knockout and provides a ½” NPT internal thread to accept the NPT cable gland. Ensure the gland OD and installation torque are compatible with the adapter body dimensions.
Q6: Are these adapters suitable for ATEX hazardous area installations?
Yes, with appropriate certification documentation. We supply adapters with the dimensional tolerances and material certifications required for Ex-e and Ex-d cable gland assemblies conforming to ATEX Directive 2014/34/EU and IECEx. Contact us for hazardous area specific requirements.
Q7: What wall thickness range can these adapters accommodate?
Standard versions accommodate enclosure wall thicknesses of 1.5 mm to 3 mm. Extended body versions are available for 3 mm to 6 mm walls or installations through gland plates or sub-plates up to 5 mm thick.
Q8: Do you supply test certificates and material reports?
Yes. Material Test Reports (MTR), RoHS and REACH compliance certificates, dimensional inspection reports, and Certificates of Conformity are issued with each lot. Third-party inspection by SGS, Bureau Veritas, or Intertek available on request.
Q9: What is the minimum order quantity for thread adapters?
Sample orders: 50–100 pieces. Commercial MOQ: 500–1000 pieces per thread combination. Custom non-standard combinations: 500 pieces minimum. Bulk orders of 10,000+ pieces/month accommodated.
Q10: Can you supply Metric × NPT adapters for oil and gas projects in the Middle East?
Yes. We regularly supply M20×M16, M20×M25, ¾” NPT × M20, 1″ NPT × M32, and other combinations to EPC contractors and distributors in Saudi Arabia, UAE, Kuwait, Oman, Qatar, and Bahrain with full export documentation including SASO-compliant packing and test certificates.
Equivalent Terms in European Languages
| Language | Equivalent Terms |
|---|---|
| Spanish | Adaptador de rosca para conduit; Ampliador de rosca para caja eléctrica; Adaptador métrico a NPT; Buje adaptador de entrada de cable |
| Russian | Резьбовой адаптер для кабельных вводов; Переходник с метрической на NPT резьбу; Адаптер кабельного ввода; Переходная втулка резьбовая |
| French | Adaptateur de filetage pour presse-câble; Réducteur-agrandisseur de filetage conduit; Adaptateur métrique NPT; Bague adaptatrice pour entrée de câble |
| Portuguese | Adaptador de rosca para eletroduto; Ampliador de entrada de cabo; Adaptador métrico para NPT; Bucha adaptadora de conduíte latão |
| Italian | Adattatore filettato per passacavi; Boccola adattatrice per conduit; Adattatore metrico NPT; Raccordo adattatore per ingresso cavi |
Related / Linked Parts and Terms
- Brass Conduit Thread Reducer Bushes (Metric to Metric and NPT)
- Brass Conduit Bushes (Standard Entry)
- Conduit Fittings – Full Range
- Flexible Conduit Adapters
- Flexible Conduit Fixed Connectors
- Flexible Conduit Swivel Connectors
- Brass Conduit Locknuts (Metric and NPT)
- Cable Glands (Type A, B, C, BW, W, E1W) per BS EN 50262
- PG Thread Adapters (PG7 to PG48)
- NPT to BSP Thread Adapters
- Conduit Couplers, Nipples, and Union Fittings
- Electrical Enclosure Blank Gland Plates
Comprehensive Thread Comparison Chart for Conduit Fittings
The following reference chart compares all major thread standards used in conduit fittings, cable glands, and electrical enclosure entries supplied by Electrical Accessories India. Use this chart to identify equivalent sizes across Metric (ISO 965-1), NPT (ANSI/ASME B1.20.1), PG (DIN 40430), and BSP (BS 2779 / ISO 228) thread systems—critical for cross-standard adapter selection in international projects.
Chart 1 – Metric ISO Conduit Threads (ISO 965-1, 1.5 mm Pitch)
| Thread Designation | Nominal OD (mm) | Pitch (mm) | Thread Form | Tolerance Class | Max Cable OD (approx.) | Typical Cable Gland Size | Conduit OD (mm) | Typical Application |
|---|---|---|---|---|---|---|---|---|
| M16×1.5 | 16.0 | 1.5 | ISO Metric Fine | 6H/6g | 7–10 mm | M16 cable gland | 16 | Small control cables, sensor wiring |
| M20×1.5 | 20.0 | 1.5 | ISO Metric Fine | 6H/6g | 10–14 mm | M20 cable gland | 20 | Control cables, instrument cables |
| M25×1.5 | 25.0 | 1.5 | ISO Metric Fine | 6H/6g | 14–18 mm | M25 cable gland | 25 | Power and control cables |
| M32×1.5 | 32.0 | 1.5 | ISO Metric Fine | 6H/6g | 18–25 mm | M32 cable gland | 32 | Medium power cables, armoured SWA |
| M40×1.5 | 40.0 | 1.5 | ISO Metric Fine | 6H/6g | 25–32 mm | M40 cable gland | 40 | Armoured cables, motor feeders |
| M50×1.5 | 50.0 | 1.5 | ISO Metric Fine | 6H/6g | 32–42 mm | M50 cable gland | 50 | Large power cables, VFD output cables |
| M63×1.5 | 63.0 | 1.5 | ISO Metric Fine | 6H/6g | 42–55 mm | M63 cable gland | 63 | HV/LV feeder cables, busbars |
| M75×1.5 | 75.0 | 1.5 | ISO Metric Fine | 6H/6g | 55–67 mm | M75 cable gland | 75 | Extra-large power cables, transformer entries |
Chart 2 – NPT Thread Sizes (ANSI/ASME B1.20.1) for Conduit Fittings
| NPT Size | Thread OD at Entry (mm) | Threads per Inch (TPI) | Thread Pitch (mm) | Taper | Nearest Metric Equivalent | Nominal Pipe Size (inches) | Typical Conduit Use |
|---|---|---|---|---|---|---|---|
| ½” NPT | 21.3 | 14 | 1.814 | 1:16 (3/4″ per ft) | M16 / M20 | ½” | Small junction box entries, instrument panels |
| ¾” NPT | 26.7 | 14 | 1.814 | 1:16 | M20 / M25 | ¾” | Control panels, NEMA 4X enclosures |
| 1″ NPT | 33.4 | 11.5 | 2.209 | 1:16 | M32 / M40 | 1″ | Motor terminal boxes, MCC panels |
| 1¼” NPT | 42.2 | 11.5 | 2.209 | 1:16 | M40 / M50 | 1¼” | Power cables, armoured cable glands |
| 1½” NPT | 48.3 | 11.5 | 2.209 | 1:16 | M50 | 1½” | Large feeder cables, oil & gas panels |
| 2″ NPT | 60.3 | 11.5 | 2.209 | 1:16 | M63 | 2″ | Heavy power cables, transformer LV panels |
| 2½” NPT | 73.0 | 8 | 3.175 | 1:16 | M75 | 2½” | Extra-large cables, substation entries |
Chart 3 – NPT × Metric Cross-Reference for Thread Adapters and Reducer Bushes
| NPT Thread (External / Male) | NPT OD at Entry (mm) | Metric Equivalent (Internal / Female) | Metric OD (mm) | Adapter Part Type | Available from EAI | Typical Use Case |
|---|---|---|---|---|---|---|
| ½” NPT | 21.3 | M16×1.5 or M20×1.5 | 16 / 20 | NPT × Metric Bush | ✔ Yes | NEMA enclosure to small metric gland |
| ¾” NPT | 26.7 | M20×1.5 or M25×1.5 | 20 / 25 | NPT × Metric Bush | ✔ Yes | Control panel retrofit, NEMA to IEC |
| 1″ NPT | 33.4 | M32×1.5 or M40×1.5 | 32 / 40 | NPT × Metric Bush | ✔ Yes | Petrochemical Ex-d junction boxes |
| 1¼” NPT | 42.2 | M40×1.5 or M50×1.5 | 40 / 50 | NPT × Metric Bush | ✔ Yes | Oil & gas feeder panels, offshore |
| 1½” NPT | 48.3 | M50×1.5 | 50 | NPT × Metric Bush | ✔ Yes | Power cable entries, LNG plant panels |
| 2″ NPT | 60.3 | M63×1.5 | 63 | NPT × Metric Bush | ✔ Yes | Large cable entries, substation panels |
| M20×1.5 | 20.0 | ½” NPT | 21.3 | Metric × NPT Bush | ✔ Yes | Metric enclosure to American NPT gland |
| M32×1.5 | 32.0 | ¾” NPT | 26.7 | Metric × NPT Bush | ✔ Yes | European panel to US spec gland |
| M40×1.5 | 40.0 | 1″ NPT | 33.4 | Metric × NPT Bush | ✔ Yes | Cross-standard MCC, power panels |
Chart 4 – PG Thread Sizes (DIN 40430) vs Metric Equivalents
PG (Panzer-Gewinde / Armoured Thread) threads per DIN 40430 are a legacy European standard still found in older switchgear and enclosures. The table below cross-references PG sizes to nearest metric equivalents for use when adapter bushes are needed.
| PG Thread Size | PG Thread OD (mm) | PG Pitch (mm) | Nearest Metric (ISO 965-1) | Metric OD (mm) | Max Cable OD for PG | Notes |
|---|---|---|---|---|---|---|
| PG7 | 12.5 | 1.27 | M12×1.5 | 12.0 | 3–6.5 mm | Very small sensor/signal cables |
| PG9 | 15.2 | 1.41 | M16×1.5 | 16.0 | 4–8 mm | Signal and small control cables |
| PG11 | 18.6 | 1.41 | M20×1.5 | 20.0 | 5–10 mm | Most common small entry size |
| PG13.5 | 20.4 | 1.41 | M20×1.5 | 20.0 | 6–12 mm | Control and instrument cables |
| PG16 | 22.5 | 1.41 | M25×1.5 | 25.0 | 10–14 mm | Mid-size control cables |
| PG21 | 28.3 | 1.41 | M25×1.5 / M32×1.5 | 25/32 | 13–18 mm | Standard power cable entry |
| PG29 | 37.0 | 1.41 | M32×1.5 / M40×1.5 | 32/40 | 18–25 mm | Armoured cables, larger entries |
| PG36 | 47.0 | 1.41 | M40×1.5 / M50×1.5 | 40/50 | 22–32 mm | Large power cables |
| PG42 | 54.0 | 1.41 | M50×1.5 | 50.0 | 30–38 mm | Heavy power cables |
| PG48 | 59.3 | 1.41 | M63×1.5 | 63.0 | 34–44 mm | Extra-large cable entries |
Chart 5 – BSP (British Standard Pipe) Threads vs Metric for Conduit Applications
BSP threads (BSPP – parallel, BSPT – taper) per BS 2779 / ISO 228 are used in older British and Commonwealth enclosures and some hydraulic-rated cable entry systems. The chart below cross-references BSP to nearest metric equivalents.
| BSP Size | Thread OD (mm) | TPI | Pitch (mm) | Thread Form | Nearest Metric Equiv. | Nearest NPT Equiv. | Application |
|---|---|---|---|---|---|---|---|
| ⅛” BSP | 9.73 | 28 | 0.907 | 55° Whitworth | M10×1.5 | ⅛” NPT | Very small cable entries |
| ¼” BSP | 13.16 | 19 | 1.337 | 55° Whitworth | M14×1.5 | ¼” NPT | Instrument and signal cables |
| ⅜” BSP | 16.66 | 19 | 1.337 | 55° Whitworth | M16×1.5 | ⅜” NPT | Small control cables |
| ½” BSP | 20.96 | 14 | 1.814 | 55° Whitworth | M20×1.5 | ½” NPT | Control panel entries, British std. |
| ¾” BSP | 26.44 | 14 | 1.814 | 55° Whitworth | M25×1.5 | ¾” NPT | Mid-size cable entries |
| 1″ BSP | 33.25 | 11 | 2.309 | 55° Whitworth | M32×1.5 | 1″ NPT | Power cables, BS std. enclosures |
| 1¼” BSP | 41.91 | 11 | 2.309 | 55° Whitworth | M40×1.5 | 1¼” NPT | Armoured cable entries |
| 1½” BSP | 47.80 | 11 | 2.309 | 55° Whitworth | M50×1.5 | 1½” NPT | Large power cables |
| 2″ BSP | 59.61 | 11 | 2.309 | 55° Whitworth | M63×1.5 | 2″ NPT | Extra-large cable entries |
Chart 6 – Thread Tightening Torque Guide for Brass Conduit Fittings
The following torque values are recommended guidelines for tightening brass conduit locknuts, reducer bushes, and adapters. Over-tightening can strip threads on thin enclosure walls; under-tightening compromises IP rating and vibration resistance. Always use calibrated torque tools for ATEX/IECEx certified assemblies.
| Thread Size | Locknut Tightening Torque (N·m) | Reducer Bush Torque (N·m) | Spanner A/F (mm) | Enclosure Wall (mm) | Notes |
|---|---|---|---|---|---|
| M16×1.5 | 5–8 | 4–6 | 22 | 1.5–3.0 | Hand-tight + ¼ turn spanner |
| M20×1.5 | 8–12 | 6–10 | 27 | 1.5–3.0 | Most common size; verify IP seal |
| M25×1.5 | 12–18 | 10–15 | 32 | 2.0–4.0 | Check washer compression |
| M32×1.5 | 18–25 | 15–20 | 41 | 2.0–4.0 | Use pin spanner for serrated type |
| M40×1.5 | 25–35 | 20–30 | 50 | 2.5–5.0 | Pin spanner recommended |
| M50×1.5 | 35–50 | 30–45 | 60 | 2.5–5.0 | Use locknut wrench, large sizes |
| M63×1.5 | 50–70 | 45–60 | 75 | 3.0–6.0 | Double locknut for Ex-d assemblies |
| M75×1.5 | 65–90 | 55–75 | 90 | 3.0–6.0 | Verify enclosure wall integrity |
| ½” NPT | 8–12 | 6–10 | 27 | 1.5–3.0 | NPT taper; hand-tight + 1–2 turns |
| ¾” NPT | 10–18 | 8–15 | 32 | 2.0–4.0 | Sealant tape optional on taper |
| 1″ NPT | 18–28 | 15–22 | 41 | 2.0–4.0 | PTFE tape on NPT recommended |
| 1½” NPT | 30–45 | 25–38 | 55 | 2.5–5.0 | Check enclosure wall clamping face |
| 2″ NPT | 45–65 | 38–55 | 70 | 3.0–6.0 | Power torque tool for large sizes |
Chart 7 – Thread Standard Summary: Conduit Fittings Global Reference
| Thread Standard | Standard Reference | Thread Angle | Thread Form | Profile | Taper / Parallel | Primary Markets | Common Conduit Use |
|---|---|---|---|---|---|---|---|
| Metric ISO Fine | ISO 965-1 | 60° | V-thread | Metric mm | Parallel | Europe, Asia, India, Middle East, Africa | Cable glands, conduit fittings, locknuts (M16–M75) |
| NPT (National Pipe Taper) | ANSI/ASME B1.20.1 | 60° | V-thread | Inches (TPI) | Taper 1:16 | USA, Canada, Saudi Arabia, some Middle East | NEMA enclosures, American conduit systems (½”–2″) |
| NPS (National Pipe Straight) | ANSI/ASME B1.20.1 | 60° | V-thread | Inches (TPI) | Parallel | USA (less common in conduit) | Straight-thread cable entry connectors |
| PG (Panzer-Gewinde) | DIN 40430 | 80° | Rounded (Rd) | mm nominal | Parallel | Germany, legacy European equipment | Old switchgear, legacy enclosures (PG7–PG48) |
| BSP Parallel (BSPP) | BS 2779 / ISO 228 | 55° | Whitworth | Inches (TPI) | Parallel | UK, Commonwealth, Australia, Middle East | British std. enclosures, BSPP cable glands |
| BSP Taper (BSPT) | BS 21 / ISO 7-1 | 55° | Whitworth | Inches (TPI) | Taper 1:16 | UK, Commonwealth | Hydraulic-rated cable entry, legacy BS panels |
| Metric Coarse (Standard) | ISO 261 / ISO 965 | 60° | V-thread | Metric mm | Parallel | Global (fasteners, not conduit) | Fixing screws, not for cable gland entries |
| UNF (Unified Fine) | ANSI/ASME B1.1 | 60° | V-thread | Inches (TPI) | Parallel | USA, Canada (aerospace, defence) | Defence panel fittings, specialist connectors |
Note: Thread dimensions shown are nominal. Always verify with calibrated Go/No-Go thread gauges before installation. For cross-standard adapter sizing, contact Electrical Accessories India with the enclosure thread standard, knockout size, cable gland thread, and enclosure wall thickness for a precise product recommendation. All brass fittings: US$ 11.50 per kilogram, CIF US Port.
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Request a Quote for Brass Thread Adapters and Enlargers
Electrical Accessories India – Manufacturer and Exporter, Jamnagar, Gujarat, India.
We supply brass thread adapters and enlargers in all Metric × Metric (M16–M75, 1.5 mm pitch) and NPT × Metric / Metric × NPT configurations to electrical OEMs, EPC contractors, panel builders, and distributors worldwide.
Contact us with your thread combination (male and female sizes/types), quantity, and destination port for a competitive CIF quotation.
Email: info@elecaccs.com | Website: www.elecaccs.com