Cable Glands: Technical Selection Guide with Sizing Charts

Cable glands are vital fittings that secure and seal cables where they enter electrical equipment. They protect terminations from dust and moisture, provide strain relief, and, for certain cable types, ensure correct earthing. This guide explains the main gland types, how they pair with common cables (SWA, 3183Y flex, YY, CY, SY), thread standards, materials, and installation tips—useful whether you’re a DIYer or an electrical contractor.

What are cable glands and why use them?

Cable glands (also called stuffing glands or cable connectors) attach to the cable and the enclosure entry. They:

• Seal and protect: Maintain the IP rating of boxes, panels, and devices by closing gaps around the cable.

• Provide strain relief: Clamp the outer sheath so any pull on the cable isn’t transferred to live terminations.

• Retain the cable: Hold it firmly in place—important with heavy cables or vibration.

• Bond screens/armour: On armoured or braided cables, metallic glands earth the armour/screen safely.

Selecting the right gland means matching it to the cable construction, overall diameter, environment (indoor/outdoor), and entry thread. A poor match risks leaks, failed strain relief, or lost earthing.

Glands by cable application

SWA (Steel Wire Armoured)

SWA needs a gland that clamps the steel armour and bonds it to earth.

• BW (indoor brass): For dry internal locations where you don’t need a weather seal on the outer sheath. The gland clamps the armour between cone and ring and is usually supplied with locknut, earth tag (banjo), and shroud.

• CW (outdoor brass): Adds a compression seal onto the cable’s outer sheath for weatherproofing (typically IP66+). Use wherever the gland is exposed to the elements or where an IP-rated outer seal is required.

Choose the gland size by the cable’s OD and armour details. The earth tag connects the gland/armour to the protective conductor. In metal enclosures, an earthing locknut can replace a separate banjo.

Rule of thumb: BW for dry internal SWA; CW for external or wet areas.

SY & CY (braided/screened control cables)

• SY: Flexible control cable with galvanised steel wire braid for mechanical protection (limited EMI benefit). The braid is not usually a safety earth.

• CY: Tinned copper braid for EMC shielding; the braid is normally bonded at one or both ends.

Use EMC/braided cable glands that provide 360° contact with the braid while sealing the outer sheath. This preserves shielding performance (CY) and neat, secure terminations (SY). Avoid plain plastic glands that simply cut the braid away—you’ll lose the shield and risk frayed strands.

YY and standard flex (e.g., 3183Y)

For unscreened, unarmoured cables use nylon dome-top (compression) glands. They grip the outer sheath, give IP sealing (often IP68 when installed correctly), and provide strain relief. They’re ideal for general panel entries and junction boxes.

Do not use plastic compression glands to terminate SWA or braided cables; they don’t bond armour/screen.

Hybrid, multi-purpose options

Newer designs simplify terminations across different cable types:

• Universal/hybrid glands (e.g., designs combining a polyamide body with metallic internals) can terminate SWA, SY, CY and unarmoured cables in one system, often to IP68, without a separate shroud. Many include faster earthing accessories (earthing locknuts or spring rings) for quick, reliable bonding.

These can cut installation time and reduce the number of variants you need to stock.

Nylon dome-top glands (IP68, unarmoured cables)

Typical clamping ranges (guide only—check the datasheet):

• M12: 3–6.5 mm

• M16: 5–10 mm

• M20: 6–12 mm or 10–14 mm (two variants are common)

• M25: 13–18 mm

• M32: 18–25 mm

Packs usually include a matching locknut for plain (non-threaded) holes.

Consumer unit tail glands

Tail glands allow two meter tails (often 25 mm²) and a main earth (typically 16 mm²) to enter through a single hole for neatness, strain relief, and to avoid eddy currents in metal boards. Look for kits with reducers to suit common knock-outs (e.g., M32/M40), inserts for multiple conductors, and IP65–IP68 ratings.

Thread standards

Most modern glands use metric threads (M12, M16, M20, M25, M32, M40, M50, M63). You may also encounter:

• PG (older German standard: PG7, PG9, PG11, etc.)

• NPT (tapered, common in North America and some hazardous-area fittings)

Match the gland to the enclosure thread, or use an adaptor. Cross-threading ruins seals and IP ratings.

Materials and finishes

• Nylon/polyamide: Light, corrosion-proof, flame-retardant; ideal for unarmoured cables.

• Brass (nickel-plated): Robust, conductive; the standard for SWA and braided/screened cables and harsher environments.

• Stainless steel: For highly corrosive or hygienic settings.

• PVC/LSZH shrouds: Used with traditional brass glands for coverage and neatness (hybrids often don’t need separate shrouds).

Choose based on environment and cable type. Outdoors or industrial? Prefer metallic or hybrid designs. Armoured/braided? You’ll need a conductive path for bonding.

Installation tips

• Size correctly: Use manufacturer charts to match gland size to cable OD and armour/braid spec.

• Prepare cleanly: Strip to the right lengths; flare braid neatly for EMC glands if required.

• Seal properly: Use sealing washers/O-rings under the gland shoulder where needed to maintain IP.

• Secure firmly: Use locknuts for plain holes; tighten to the recommended torque.

• Bond safely: On armoured/braided terminations, fit the earth tag/earthing locknut and connect to the earth bar—always run a dedicated earth in plastic enclosures.

• Inspect: Check even clamping of armour/braid, compressed seals, and perform a tug test.

Quick selection workflow

1. Identify the cable: SWA / SY / CY / YY / 3183Y flex.

2. Set the environment: Internal dry vs external/wet and target IP.

3. Pick the gland type:

   • SWA: BW (indoor) or CW (outdoor).

   • SY/CY: EMC/braided gland with 360° contact.

   • YY/flex: nylon dome-top.

   • Mixed/fast-fit needs: hybrid/universal gland.

4. Match the thread: Prefer metric; adapt PG/NPT only if necessary.

5. Choose materials: Nylon for unarmoured; nickel-plated brass/hybrid or stainless for armour/braid or harsh sites.

6. Confirm size and accessories: Check OD range, add locknut, sealing washer, shroud/earthing parts as required.

Selecting the right gland—and fitting it correctly—protects your wiring, preserves enclosure IP ratings, and ensures safe earthing where needed. If you’re unsure on sizing, share the cable type and overall diameter and a supplier can match an appropriate gland or kit.

For more information on Cable Glands: Technical Selection Guide with Sizing Charts talk to Expert Electrical Supplies Ltd