Cable gland selection starts with three independent numbers: cable outside diameter (OD), enclosure thread, and required IP rating, because a wrong fit on any one of them voids the seal regardless of how good the other two are [S1][S4].
IEC 62444 governs cable-gland product design, with thread forms per ISO 965 (Metric) and DIN 40430 (PG), and the same size code (e.g. M20×1.5) means the same thread worldwide even when sealed cable ranges differ by design [S4]. For more on the broader sealing and packing discipline used in process piping, see gland packing.
Match the Gland to the Cable OD and Thread
The sealing insert grips the cable jacket, not the conductor bundle, so the gland's stated clamping range must bracket the measured cable OD, ideally with the OD landing near the middle of the range for tolerance on jacket variation [S2][S4].
Common Metric sizes for industrial work: M12×1.5 seals 3–6.5 mm, M16×1.5 seals 4–8 mm, M20×1.5 seals 6–12 mm, M25×1.5 seals 10–14 mm, M32×1.5 seals 15–22 mm, M40×1.5 seals 18–25 mm, M50×1.5 seals 32–38 mm, and M63×1.5 seals 37–44 mm [S4]. PG11 covers 5–10 mm and is still dominant in older European control gear [S4]. NPT threads, identified by tapered 1.5 mm pitch on 1/2" or 3/4", suit North American enclosures and require thread sealant to reach a real IP rating [S6].
Split cable glands are the right pick when the cable is pre-terminated with an M8/M12, RJ45, USB, HDMI, or D-sub connector that cannot be removed, because a two-part body and split sealing insert close around the cable after routing [S2]. When several connectorized cables must share one cut-out, a multi-cable split gland or modular entry frame usually beats adding single holes [S2].
IP Rating and Enclosure Compatibility
Always select a gland with an IP rating at least equal to, and preferably one step above, the enclosure rating, because the enclosure's IP figure is only as good as its weakest penetration [S1][S5]. An IP65 enclosure should use IP67 glands; IP66 wash-down areas should use IP68 glands where practical [S1].
Ingress ratings and what they actually demand: IP65 resists low-pressure water jets, IP66 resists heavy seas, IP67 tolerates temporary immersion to 1 m for 30 min, and IP68 specifies continuous immersion under a defined depth and time agreed between supplier and buyer [S5]. For outdoor junction boxes, machine power entries, and food-and-beverage wash-down zones, the practical floor is IP67 with stainless or nickel-plated brass hardware [S4].
Material choice ties directly to environment: nylon (PA66) covers most indoor control panels at low cost; brass handles outdoor and chemical exposure; SS304 suits general corrosive areas; SS316 is the default for marine, offshore, and food-grade wash-down [S4][S5]. For comparison shopping on the cable itself, the cable and wire reference breaks down jacket materials, while control cable and power cable pages list the typical OD and construction that drive gland sizing in cabinets and feeders.
Armoured, EMC, and Special Cable Construction
On armoured cable, the gland must grip the steel-wire armour or braid to maintain protective-earth continuity, because the body contacts the enclosure metalwork and the armour becomes part of the earth-fault path without a separate bonding conductor [S5]. A single-compression gland seals the outer sheath only; a double-compression design adds an armour cone or clamping ring to bite the metal layer [S5].
EMC glands carry a 360° shielded contact that bonds the cable screen to the enclosure at low impedance, which matters for VFD-driven motors, instrumentation, and any cable carrying fast-edge signals near sensitive analogue loops [S3]. Purpose-designed EMC or armoured glands must be used, not improvised with tape or sealant [S2]. For installations where the gland also routes cable tray entry or where shielded control cable glands are stacked on a gland plate, follow the same earth-bonding discipline at every entry.
Thread Standard, Cut-Out, and Mounting Method
Confirm the cut-out diameter, thread type, thread pitch, usable thread length, and the supplied locknut or O-ring before ordering; the gland must match the existing cut-out rather than just the product name [S2]. Identifying an unknown gland comes down to measuring the OD and pitch with a caliper and thread gauge: 1.5 mm pitch on a 20 mm OD is Metric M20×1.5, while the 1.5 mm pitch on a 1/2" or 3/4" OD with a taper is NPT [S6].
Common mistakes: using a PG thread where the panel is drilled Metric (the body will not seat), using a NPT in a Metric cut-out (the taper will not seal without a thread sealant rated for the chemical exposure), and confusing NPSL straight pipe threads with NPT tapered threads [S6]. When in doubt on retrofit, use a thread pitch gauge, not a visual match, and order the matching locknut, washer, and earthing tag from the same supplier [S2][S5].
Options Compared: Nylon vs Brass vs Stainless vs Split
For a clean selection, line the four common options against the four criteria that drive most spec decisions:
Nylon (PA66): lowest cost, indoor use, light weight, non-conductive; typical IP68 ratings are achievable on Metric threads but UV and chemical resistance are limited, so outdoor or solvent-exposed zones need a different material [S4].
Brass (nickel-plated): the default outdoor and industrial option, good chemical and UV resistance, accepts both Metric and PG threads, and provides a reliable earth path when used with armoured cable; cost is moderate, lead time short [S4].
Stainless 304/316: required for marine, offshore, food-and-beverage wash-down, and chemical plants; SS316 is the safe default for salt exposure; cost is the highest of the four but service life under corrosion justifies the premium in those zones [S4].
Split gland: the only realistic pick when the cable arrives with a factory-fitted connector (M12, RJ45, HDMI, D-sub); lower IP ceiling than solid-body equivalents in some designs, so verify the rating against the enclosure requirement before buying [S2].
Who should NOT pick the mainstream option: a brass gland on a food line that sees daily chlorinated wash-down will fail the corrosion check, an SS316 gland on an indoor control panel is overspent budget, and a nylon gland on a rooftop solar feeder will degrade under UV. Match material to environment before matching size to cable.
Limitations, Failure Modes, and Sourcing
Most field leaks on a "waterproof" entry trace back to one of four causes: cable OD outside the insert range, missing or wrong O-ring, under-torqued compression nut, or wrong thread standard for the drilled hole [S1][S4]. Filling a gap with tape, sealant, or an improvised sleeve breaks the gland's stated IP unless the manufacturer explicitly documents the method [S2].
Sourcing checklist before issue of a PO: cable OD with caliper, thread standard and pitch, panel cut-out diameter, enclosure IP rating, gland IP rating (one step above enclosure), material suited to environment, armoured/EMC construction if applicable, and matching locknut, washer, and earthing tag [S2][S3]. For shielded and armoured feeders running through a cable tray system, the related shielded cable selection walkthrough covers the screen-bonding and EMC gland pairing for industrial buyers.
Final two signals to track in the next procurement cycle: IEC 62444-aligned shortlists for M20 and M25 sizes (the workhorse sizes in 3–5 core control and light power), and a verified SS316 offering for M20 and M25 with documented IP68 immersion depth and time, since most wash-down audits fail on that exact data point [S4].