UK How a cable gland works
A cable gland is a threaded fitting that carries a cable through a hole in an enclosure wall and seals around it. It does three jobs at once: it keeps dust and water out, it grips the cable so that a pull or twist is taken by the gland rather than the terminals inside, and it protects the cable from the sharp edge of the hole.
Most glands share the same basic parts. The body screws into a tapped hole or is held by a locknut on the inside. A rubber seal or insert sits inside the body around the cable. When the dome nut (cap nut) is tightened, it squeezes the seal against the cable, often through a set of plastic fingers that also clamp it. A flat washer or O-ring under the body seals the gland to the enclosure wall.
Every gland is made for a clamping range: the smallest and largest cable outer diameter it can seal. A cable outside that range will either not grip or not seal, whatever the thread size.
Types of cable gland
Glands are grouped by material and by any extra job they do beyond sealing.
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Nylon (polyamide) glands. Light, low cost and corrosion free. The usual choice for control panels, junction boxes and light industrial equipment, often rated IP68.
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Nickel-plated brass glands. Stronger and more resistant to heat and impact. Common on machinery and outdoor cabinets.
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Stainless steel glands. 304 or 316 stainless for food, pharmaceutical, marine and chemical sites. Hygienic designs have smooth outer surfaces with no crevices, so they can be cleaned in place.
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Armoured cable glands. Made for steel wire armoured (SWA) cable. They clamp and earth the armour, and outdoor types add an outer seal over the cable sheath.
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EMC glands. Make a 360° contact with the cable’s braided screen and bond it to a metal enclosure, which keeps electromagnetic interference out of sensitive electronics.
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Hazardous-area glands. Certified Ex glands keep the protection of an Ex d flameproof or Ex e increased-safety enclosure intact, and carry ATEX or IECEx markings.
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Split and multi-hole glands. Let pre-terminated cables, such as Ethernet or USB leads with moulded plugs, pass through and seal without cutting the connector off.
Cable gland sizes and threads
A gland is specified by two numbers: the entry thread that fits the enclosure, and the clamping range that fits the cable. Three thread systems are in common use.
| Thread system | Defined by | Common sizes | Thread form | Where you see it |
|---|---|---|---|---|
| Metric (M) | IEC 60423 / EN 60423 | M12, M16, M20, M25, M32, M40, M50, M63 (all 1.5 mm pitch) | Parallel | UK, Europe and most new equipment worldwide |
| PG (Panzergewinde) | DIN 40430 | PG7, PG9, PG11, PG13.5, PG16, PG21, PG29 | Parallel, 80° flank | Older German and European equipment |
| NPT | ASME B1.20.1 | 1/2″, 3/4″, 1″, 1-1/4″ | Tapered | North America, often alongside conduit |
Metric glands are named by thread diameter, so an M20 has a 20 mm thread. PG sizes do not match their thread diameter, and a PG gland will not screw into a metric hole of a similar size. NPT threads taper and seal on the thread itself, while metric and PG threads are parallel and seal on a washer or O-ring. Clamping ranges vary by maker; an M20 nylon gland, for example, typically seals cables of roughly 6–12 mm, and larger cables step up to M25 or M32. Check the gland datasheet against the measured cable diameter, not the conductor size.
Cable gland vs connector on sealed computers
A sealed computer or display has to bring power, network and I/O through its enclosure without losing its IP rating. There are two ways to do it, and both are common on washdown and outdoor equipment.
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Glands into a sealed compartment. Standard cables pass through glands into a sealed rear compartment or conduit box, where they plug into ordinary RJ45, USB and serial ports. Field cabling is simple and standard leads can be used, but the compartment has to be opened, resealed and checked whenever a cable changes. Some of our IP69K panel PCs use this layout, with the ports inside a sealed conduit area.
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Sealed circular connectors. Each port is an M12 or similar sealed connector on the enclosure, so cables plug in from outside and the enclosure stays closed. Connection and replacement are quicker, but each lead needs an M12 plug, and the other end of the cable still needs protecting. Our white paper on M12 waterproof connectors explains where that approach works best.
Standards and ratings for cable glands
In the UK and Europe, cable glands for general electrical installations are covered by IEC 62444, published as BS EN 62444, which sets the mechanical, retention and sealing tests. The IP rating of a gland is proven to IEC 60529 like any enclosure, and good glands are commonly rated IP66 to IP68, with some stainless designs also tested to IP69K. In the US, cable fittings are listed to UL 514B. Glands for explosive atmospheres follow the IEC 60079 series and are certified under ATEX in the UK and EU (UKEX in Great Britain) or IECEx internationally.
A gland’s rating applies only when it is fitted to a cable within its clamping range and tightened as specified. The installed rating of a computer or cabinet can never be higher than its weakest gland, so our IP rating chart is a useful check when matching glands to an enclosure.
Quick answers on cable glands
Cable glands: common questions
What is a cable gland used for?
To seal and secure a cable entry. It keeps dust and water out of an enclosure, holds the cable against pulling and twisting, and protects it from the edge of the hole.
What is another name for a cable gland?
Cable connector, cord grip or strain relief fitting. In North America “cord grip” and “cable connector” are common; in the UK “gland” is the usual term.
What size cable gland do I need?
Measure the cable’s outside diameter first. Choose a gland whose clamping range includes that diameter, then match its thread to the enclosure entry, such as M20 or PG13.5.
What is an EMC cable gland?
A metal gland that bonds the cable screen to the enclosure. It makes a 360° contact with the braid, which keeps the shield effective where the cable enters.
How do you fit a cable gland?
Drill, fit, pass, tighten. Drill or tap the entry, fit the body with its washer and locknut, pass the cable through, then tighten the dome nut to the maker’s torque until the seal grips.
We specify the cable entries for every sealed computer and display we supply, whether glands, sealed conduit or M12 connectors, and check them against the enclosure’s IP rating and the site’s cabling as standard before the system ships.