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Stainless Steel Lock Nuts for Cable Glands
Stainless Steel Lock Nuts for Cable Glands — SS316 and SS304 Metric and NPT Cable Gland Locknuts
Stainless Steel Lock Nuts for Cable Glands (also referred to as stainless steel cable gland locknuts, SS gland lock nuts, stainless steel gland retaining nuts, or SS cable entry lock rings) are precision-machined fastening components that secure cable glands, conduit connectors, and cable entry fittings into electrical enclosure walls, junction box panels, switchgear cabinets, and process equipment housings. Manufactured from AISI 316 (Grade 316, 1.4401) and AISI 304 (Grade 304, 1.4301) austenitic stainless steel, these locknuts are produced in metric thread series (M12 to M63, per ISO 965-1) and NPT thread series for full compatibility with stainless steel cable glands in marine, offshore, chemical, food processing, pharmaceutical, and hazardous area installations where the use of brass or nickel-plated brass locknuts would be inadequate due to corrosion risk. Electrical Accessories India manufactures stainless steel cable gland locknuts in hexagonal, round (spanner-ring), and sealing-washer integrated profiles to match all standard cable gland product ranges. Price: US$ 10.90/Kilogram
Product Overview
Function and Design of Cable Gland Lock Nuts
The cable gland locknut is the rear-face fastening element of a cable gland assembly. When a cable gland is inserted through an enclosure wall entry hole (drilled, punched, or tapped), the locknut is threaded onto the gland body thread from the inside face of the enclosure and tightened to the specified installation torque to secure the gland and compress the enclosure-face O-ring (on parallel-thread metric glands) for IP sealing. The locknut functions simultaneously as: (a) mechanical retention — resisting pull-out forces on the gland body from cable weight, cable movement, and vibration; (b) IP sealing pressure — applying compressive load on the enclosure-face O-ring to achieve the rated IP66/67/68 sealing; (c) earthing contact (metallic enclosures) — providing metallic continuity between the gland body and enclosure metalwork for protective earth and EMC bonding; and (d) torque control — the locknut’s geometry determines the applied installation torque and ensures consistent gland-to-enclosure engagement across multiple installations. Stainless steel locknuts are machined to the same thread dimensions as the gland body thread, ensuring correct engagement without thread galling — a critical consideration with stainless steel (anti-galling thread lubricant is recommended during installation).
Hexagonal vs Round (Spanner Ring) Lock Nut Profiles
Cable gland locknuts are manufactured in two primary external profiles depending on the enclosure internal space available and the installation tool preferred. Hexagonal profile locknuts (hex locknuts) are the most common type — driven by standard metric spanners, adjustable spanners, or socket wrenches; hex profile enables precise torque wrench installation for consistent gland clamping; hex AF (across-flats) dimensions follow standard metric hex nut sizing (e.g., M20 hex locknut has 27 mm AF). Round profile locknuts (spanner-ring locknuts, round locknuts, or C-wrenched locknuts) have a cylindrical profile with two or four radial slots or notched edges for engagement by a spanner hook, pin spanner, or special locknut installation tool; round locknuts are used when enclosure internal space is insufficient for hex spanner engagement, particularly in densely populated enclosures with multiple cable entries and closely spaced glands. Both hex and round profiles are machined from SS316/304 bar stock on CNC turning and milling centres to identical thread tolerances.
Metric Thread Locknuts: M12 to M63
Stainless steel cable gland locknuts are produced in the full metric range matching IEC-standard cable gland thread sizes: M12, M16, M20, M25, M32, M40, M50, and M63. For each size, the internal thread (mating with the gland body external thread) is machined to ISO 965-1 tolerance class 6H (standard nut thread). The locknut thickness (height) is specified to ensure adequate thread engagement — minimum 1.5× pitch engagement is maintained for all sizes. Locknut outer profile dimensions: hex AF follows DIN 934 (ISO 4032) nut standard dimensions as a reference but with modified height for cable gland application; round profile OD is typically 95–100% of the enclosure KO diameter to maximize the sealing footprint on the enclosure inner face. Stainless steel locknuts are compatible with the full range of IEC-standard cable glands from Electrical Accessories India and standard metric cable glands from all major manufacturers (CMP, Hawke, Jacob, Roxtec, Wiska, Lapp).
NPT Thread Lock Nuts for American and API-Spec Equipment
For NPT-threaded cable glands and conduit connectors used in NEMA enclosures and API-specification process equipment, stainless steel NPT locknuts (1/2″ to 2″ NPT, ASME B1.20.1) are produced. NPT locknut geometry differs from metric — because NPT is a tapered thread, the locknut does not seal at its own thread; rather, it acts as a retaining jam nut against the enclosure inner face, providing mechanical retention and torque loading. NPT SS locknuts in hex and round profiles are supplied as a set with NPT SS cable glands for complete assembly.
Sealing Washer Integrated Lock Nuts (Earthing/Sealing Profile)
Some cable gland installations require an earthing bond between the gland body and the metallic enclosure in addition to mechanical retention. Integrated sealing/earthing locknuts combine: the locknut body (SS316); a nylon or stainless steel flat washer bonded to the locknut face; and an optional integral star earth washer (serrated, SS316) that bites through enclosure surface coatings to ensure metallic contact for earth bonding and EMC performance. These integrated assembly locknuts simplify installation by eliminating separate washer handling in field installation environments and are particularly valuable for marine and offshore panel assembly where component handling is difficult. IP sealing between the locknut face and the enclosure inner surface is achieved by the nylon washer or EPDM sealing washer bonded to the locknut contact face — providing inner-face IP contribution to the cable gland’s overall IP rating.
Anti-Galling and Thread Lubrication for SS Locknuts
Stainless steel thread galling (cold welding/seizing) is a critical consideration with austenitic stainless steel fasteners (including locknuts). When two stainless steel surfaces (gland body thread and locknut thread) slide against each other under load, the protective oxide layer can be locally disrupted, causing metal-to-metal adhesion (galling) that can seize the fastener permanently — even at correct installation torque. To prevent this, all Electrical Accessories India stainless steel locknuts are supplied with the recommendation for anti-galling thread lubricant (nickel-based anti-seize, Molykote D-Paste, or food-grade equivalent) at the gland-locknut thread interface during installation. Where anti-galling is critical (installation at elevated temperature, repeated assembly/disassembly), PTFE-coated stainless steel locknuts or A4 (316) grade locknuts with passivated thread are specified. Alternative: use of a dissimilar pair (SS316 gland + A2/304 locknut) reduces galling risk while maintaining corrosion resistance in most environments.
Electrical Earthing and Bonding Through SS Lock Nuts
In metallic enclosures (stainless steel, steel, or aluminium), the cable gland locknut provides the metallic continuity path between the gland body (and thus the cable armour or conduit connected to it) and the enclosure body. This path is critical for: protective earth continuity (PE) — required by IEC 60364-5-54 and IEE Wiring Regulations; EMC cable shielding — the 360° metallic contact of the locknut to the enclosure inner face at the cable entry point is part of the EMC bonding chain for cable screen earthing. Stainless steel locknuts provide lower contact resistance at the locknut-to-enclosure interface than zinc-plated steel or nickel brass locknuts in corrosive environments, where non-SS locknuts develop resistive oxide layers over time. For critical earthing applications, the SS locknut contact face is supplied with machined (not oxidised) contact area and the mating enclosure entry face should be locally cleaned or fitted with a serrated earth washer.
Corrosion Resistance Comparison of Locknut Materials
| Material | Salt Spray (hrs, ISO 9227) | Marine Suitability | Chemical Suitability | Food Grade |
|---|---|---|---|---|
| SS 316 (1.4401) | >5,000 | Excellent | Very Good | Yes (with EP) |
| SS 304 (1.4301) | >2,000 | Good (non-chloride) | Good | Yes |
| Nickel-plated Brass | 400–600 | Limited | Poor | No |
| Zinc-plated Steel | 96–200 | No | Poor | No |
| Hot-dip Galv Steel | 500–1000 | Limited | Poor | No |
Dimensional Standards and Compatibility
Stainless steel cable gland locknuts are produced to compatible dimensions for all major cable gland standards. Thread size and profile match IEC 62444 / BS 6121 metric gland threads. Hex AF dimensions follow DIN 934 reference as standard. Round profile OD is matched to IEC 60423 knockout dimensions for enclosure inner-face seating. Thread tolerances: 6H per ISO 965-1. Locknuts from Electrical Accessories India are tested for thread engagement compatibility with our own SS cable glands and with standard metric cable glands from the market.
Key Features
- AISI 316 (1.4401) and AISI 304 (1.4301) stainless steel for marine, chemical, and food-grade environments
- Full metric range M12 to M63 matching all standard IEC cable gland sizes
- NPT sizes 1/2″ to 2″ for NEMA and API-specification equipment
- Hexagonal and round (spanner ring) profiles for full enclosure access compatibility
- Integrated sealing/earthing locknuts with bonded nylon washer and optional star earth washer
- ISO 965-1 Class 6H thread — precision thread for secure gland engagement
- Anti-galling recommendations supplied with all SS locknut orders
- ISO 9001:2015 certified manufacturing; material certificates supplied
Thin-Profile Lock Nuts for Dense Panel Installations
For enclosures with high gland density (multiple glands in a restricted wall area), thin-profile (low-height) stainless steel locknuts are produced — these have reduced hex height (typically 40–50% of standard) to allow adjacent gland locknuts to be tightened without spanner interference. Thin-profile locknuts maintain the same thread engagement and mechanical retention as standard but require controlled torque application (lower than standard torque, with thread engagement verification) due to reduced nut height.
Large-Diameter Lock Nuts (M50, M63)
Large-diameter SS locknuts (M50 and M63) for large cable glands (used on cables 35 mm to 55 mm OD) are produced with extended hex AF or larger round profile for adequate spanner grip. The larger sizes require proportionally higher installation torque (up to 80–120 Nm) — torque wrench installation is strongly recommended. These large locknuts are used in power feeder cable entries on transformers, large MCC panels, and offshore power distribution boards.
Stainless Steel Lock Nuts as Replacement Hardware
Stainless steel locknuts are frequently specified as replacement hardware on existing installations where original brass or steel locknuts have corroded and require replacement without replacing the cable gland itself. Provided the gland body thread is in good condition, an SS locknut can directly replace a brass locknut of the same thread size. This is a common maintenance practice in marine, coastal, and chemical plant electrical systems upgrading to SS hardware for extended service life.
Lock Nut Material Selection Guide
| Environment | Recommended Locknut Grade | Surface Finish |
|---|---|---|
| Marine / Offshore (seawater exposure) | AISI 316 (1.4401) | Passivated |
| Chemical plant (acid/chloride) | AISI 316 / 316L | Passivated |
| Food / Dairy / Pharma | AISI 316 (1.4401) | Electropolished |
| Outdoor substation / coastal | AISI 316 | Passivated |
| Indoor industrial panel | AISI 304 (1.4301) | Machined |
| Cleanroom / pharmaceutical | AISI 316 (1.4401) | Electropolished |
Technical Specifications
| Parameter | Specification |
|---|---|
| Material | AISI 316 (1.4401) / AISI 304 (1.4301) |
| Thread Standard (Metric) | M12, M16, M20, M25, M32, M40, M50, M63 per ISO 965-1 |
| Thread Standard (NPT) | 1/2″, 3/4″, 1″, 1-1/4″, 1-1/2″, 2″ per ASME B1.20.1 |
| Thread Tolerance | 6H (internal, ISO 965-1) |
| Profile Options | Hexagonal (hex AF per DIN 934 reference) / Round (spanner ring) |
| Height Options | Standard / Thin-profile (40–50% reduced height) |
| Surface Finish | Machined (Ra 1.6 µm) / Passivated / Electropolished (Ra ≤ 0.8 µm) |
| Temperature Rating | -60°C to +300°C (continuous, SS body) |
| Salt Spray Resistance (SS316) | >5,000 hours (ISO 9227) |
| Compatible With | All EN 62444 / BS 6121 metric cable glands |
| Price | US$ 10.90/Kilogram |
Stainless Steel Grade and International Equivalents
| Grade | EN (Europe) | UNS (USA) | BS (UK) | IS (India) | Application |
|---|---|---|---|---|---|
| AISI 316 | 1.4401 | S31600 | 316 S 31 | IS 6911 SS316 | Marine, offshore, chemical, food |
| AISI 316L | 1.4404 | S31603 | 316 S 11 | IS 6911 SS316L | Highly corrosive, max corrosion resist |
| AISI 304 | 1.4301 | S30400 | 304 S 31 | IS 6911 SS304 | Indoor industrial, pharmaceutical |
Metric Lock Nut Size Reference Table
| Thread Size | Hex AF (mm) | Round OD (approx.) | Standard Height (mm) | Compatible Gland Range |
|---|---|---|---|---|
| M12 | 19 | 17 mm | 5 | M12 cable glands |
| M16 | 22 | 21 mm | 6 | M16 cable glands |
| M20 | 27 | 26 mm | 7 | M20 cable glands |
| M25 | 32 | 31 mm | 8 | M25 cable glands |
| M32 | 41 | 38 mm | 9 | M32 cable glands |
| M40 | 50 | 47 mm | 10 | M40 cable glands |
| M50 | 60 | 57 mm | 12 | M50 cable glands |
| M63 | 75 | 72 mm | 14 | M63 cable glands |
Product Types and Variants
| Type | Thread | Profile | Material | Application |
|---|---|---|---|---|
| Standard Hex Locknut | Metric M12–M63 | Hexagonal | SS316 / SS304 | General cable gland retention |
| Round Spanner Locknut | Metric M12–M63 | Round (slotted) | SS316 / SS304 | Dense panel installations |
| Thin-Profile Hex Locknut | Metric M16–M40 | Hexagonal, reduced height | SS316 / SS304 | High-density cable entries |
| Integrated Sealing Locknut | Metric M16–M50 | Hex with bonded nylon washer | SS316 | IP contribution at inner face |
| Earthing Locknut | Metric M16–M50 | Hex with star earth washer | SS316 | EMC and PE earthing continuity |
| NPT Hex Locknut | NPT 1/2″–2″ | Hexagonal | SS316 / SS304 | NEMA, API-spec equipment |
| Electropolished (Food Grade) | Metric M16–M50 | Hex or round | SS316 (EP) | Food, dairy, pharma installations |
Applications in Industry
| Industry | Application | Grade | Profile |
|---|---|---|---|
| Marine / Offshore | Junction box, switchboard cable gland locknuts | SS316 | Hex / Round |
| Oil and Gas | ATEX Zone 1/2 panel locknut replacement hardware | SS316 | Hex |
| Chemical Processing | Corrosive environment panel cable gland hardware | SS316 / 316L | Hex |
| Food and Beverage | IP69K washdown panel locknut hardware | SS316 (EP) | Hex / Round |
| Pharmaceutical | Cleanroom panel and equipment cable entries | SS316 (EP) | Hex |
| Water / Wastewater | Wet well, treatment plant panel hardware | SS316 | Hex |
| Power Utilities | Outdoor substation, coastal switchgear | SS316 / SS304 | Hex |
| Maintenance / Upgrade | Replacement for corroded brass/steel locknuts | SS316 | Hex / Round |
Manufacturing Process
Stainless steel cable gland locknuts are CNC-machined from certified SS316 or SS304 bar stock. Process: (1) Material incoming inspection — mill test certificate (MTC) review including chemical composition (Mo content verification for SS316) and mechanical properties; PMI (XRF) spot check on each batch; (2) CNC turning — locknut OD profile, internal thread, and face chamfer machined in one or two setups; (3) Hex milling — AF flats machined on CNC milling centre (for hex profile locknuts); slot milling — radial slots machined for round spanner profile; (4) Thread gauging — internal thread verified by ISO 965-1 go/no-go thread gauge on every locknut; (5) Deburring — all thread entry chamfers and machined edges deburred; (6) Passivation — citric acid bath per ASTM A967; (7) Electropolishing (food/pharma grade) per ASTM B912 — Ra ≤ 0.8 µm; (8) Washer bonding (for integrated sealing locknuts) — nylon or EPDM sealing washer bonded to locknut contact face; (9) Dimensional inspection — thread, OD, height, and AF per inspection plan; (10) Batch marking and packaging — size, material grade, and lot number marked; individual polybag or tray-packed in carton.
Quality Standards and Certifications
| Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 965-1 | Metric thread tolerances — Class 6H internal thread |
| ASME B1.20.1 | NPT thread standard |
| ASTM A967 / A380 | Passivation of stainless steel parts |
| ASTM B912 | Electropolishing of stainless steel |
| EN 10204 3.1 | Material test certificate for SS bar stock |
| ISO 9227 | Salt spray corrosion resistance testing |
| EN 62444 / BS 6121 | Cable gland dimensional compatibility (for locknut sizing) |
Why Choose Electrical Accessories India?
- Full Size Range M12–M63 — complete metric range for all IEC cable gland sizes from one source
- Both SS316 and SS304 — marine-grade and general-purpose grades available, PMI-verified
- Hex and Round Profiles — both installation profiles for dense and standard panel applications
- Integrated Sealing and Earthing — locknuts with bonded sealing washer and earth washer options
- Food Grade Electropolished — SS316 EP locknuts for hygienic panel installations
- Drop-In Replacement — dimensional compatibility with all major cable gland brands
- Price: US$ 10.90/Kilogram — competitive for marine, chemical, and offshore MRO procurement
Frequently Asked Questions
Q1. Do SS locknuts fit all brands of cable glands?
Yes, for the same metric thread size. Cable gland locknuts are threaded to ISO 965-1 Class 6H, compatible with all cable glands whose external body thread conforms to ISO 1502 metric thread standard. Our locknuts have been checked for compatibility with CMP, Hawke, Jacob, Lapp, and standard metric cable glands. For specific brand compatibility verification, please provide the gland brand and size.
Q2. Can SS locknuts replace brass locknuts on existing cable glands?
Yes. Stainless steel locknuts can directly replace brass, nickel-plated brass, or zinc-plated steel locknuts of the same thread size. This is a common upgrade practice for marine, coastal, and chemical plant installations. Apply anti-seize thread lubricant to the SS-to-SS interface to prevent galling if the gland body is also stainless steel.
Q3. What is the risk of galling with SS locknuts on SS cable glands?
Thread galling (seizing) between two SS surfaces is a real risk if dry-threaded without lubricant and if over-torqued. To prevent galling: always use anti-seize thread lubricant (nickel-based anti-seize, Molykote D-Paste, or food-grade equivalent) on the thread; tighten to specified torque and stop; avoid repeated assembly/disassembly dry. Using a SS304 locknut with an SS316 gland (dissimilar pair) reduces galling risk while maintaining corrosion resistance in most environments.
Q4. What is the difference between standard height and thin-profile locknuts?
Standard height locknuts have full thread engagement depth (1.5–2.5× pitch) and specified installation torque. Thin-profile locknuts have 40–50% reduced height — for use where enclosure internal space is restricted and adjacent glands prevent full-height locknut installation. Thin-profile locknuts require reduced installation torque and should be verified for adequate thread engagement before use in vibration or high-cable-weight applications.
Q5. Are integrated sealing locknuts (with bonded washer) available?
Yes. SS316 locknuts with pre-bonded nylon sealing washer on the inner enclosure face are available for M16 to M50 sizes. These simplify installation (no separate washer to handle) and provide consistent inner-face IP contribution when the gland O-ring seals the outer face. EPDM sealing face options are available for IP68 applications.
Q6. Do you supply earthing/bonding locknuts?
Yes. SS316 hex locknuts with integrated serrated (star) earth washer on the contact face are available for M16–M50. The serrated earth washer bites through enclosure paint and surface coatings at installation, establishing direct metal-to-metal earth contact. These are used where the gland body earthing continuity to the enclosure is required per IEC 60364-5-54 and IEE Wiring Regulations.
Q7. What is the minimum order quantity?
Standard hex locknuts (M16–M40, SS316 passivated): MOQ 100 pieces. Round profile locknuts: MOQ 50 pieces. Large sizes (M50, M63): MOQ 25 pieces. Integrated sealing/earthing locknuts: MOQ 50 pieces. Sample quantities (10–20 pieces) for specification trials and approval are available.
Q8. Can you supply complete cable gland kits (gland + locknut + washer)?
Yes. Complete cable gland kits including SS cable gland body + SS locknut + SS flat washer + sealing insert are available as pre-packed kits for M16 to M50 in SS316 and SS304. Kits are supplied in individual polybags with part number and batch label for field installation traceability.
Equivalent Terms in Other Languages
| Language | Term 1 | Term 2 | Term 3 |
|---|---|---|---|
| Spanish | Contratuercas inox para prensaestopas | Tuercas de bloqueo acero inoxidable | Contratuercas de cable inoxidable |
| Russian | Контргайки из нержавеющей стали для кабельных вводов | Гайки блокировочные нержавейка | Стопорные гайки нержавеющая сталь |
| French | Contre-écrous inox pour presse-étoupes | Écrous de blocage acier inoxydable | Bagues de serrage inox câble |
| Portuguese | Contraporcas inox para prensa-cabos | Porcas de bloqueio aço inoxidável | Contraporcas de cabo inox |
| Italian | Controdadi inox per pressacavi | Dadi di bloccaggio acciaio inossidabile | Ghiere di serraggio inox |
Related Stainless Steel Products
- Stainless Steel Cable Glands (Metric and NPT)
- Stainless Steel Glands and Connectors for Flexible Conduits
- Cable Glands Accessories (Brass)
- Cable Glands (Brass)
- Aluminum Machined Washers
Get a Quote — Stainless Steel Lock Nuts for Cable Glands
Specify thread size (M_), material grade (SS316/SS304), profile (hex/round), height (standard/thin), finish (passivated/electropolished), and quantity. For replacement orders, specify the cable gland brand and size to confirm compatibility.
Price: US$ 10.90/Kilogram | MOQ: 25–100 pcs | Gujarat, India | Global Export
