Cable Gland Selection Guide: Thread, IP Rating & Armoured Cable Compatibility Get a cable gland wrong and the failure shows up later, not immediately — as water ingress six months on, a stripped thread on installation, or an armoured cable's steel wire braid left without a proper earth continuity path. Three things decide whether a gland is right for the job: the thread type matching the enclosure entry, the clamping range matching the actual cable outer diameter, and — for armoured cable — a construction that properly terminates and earths the armour rather than just gripping the outer sheath. This guide walks through all three, plus IP rating and material selection, so you can specify the right gland the first time rather than discovering a mismatch on site. Talk to Our Expert Team What a Gland Actually Has to Do A cable gland has three jobs at once: seal the cable entry against dust and water ingress to maintain the enclosure's IP rating, mechanically clamp and strain-relieve the cable so pulling on it doesn't stress the terminations inside, and — on armoured cable — provide a continuous, low-resistance earth path from the cable's armour or braid through to the enclosure. A gland that only does the first two jobs but leaves the armour unterminated or poorly earthed has quietly removed a safety-critical fault path without anyone noticing until there's a fault to clear. Cross-section of an armoured cable gland showing the outer seal, armour clamping ring providing earth continuity, and inner seal on the cable core An armoured cable gland clamps the outer sheath for strain relief and sealing, clamps the steel wire armour separately to provide earth continuity to the enclosure, and seals around the inner cable core. Enclosure Gland body Armour clamp Earth continuity to enclosure Outer seal Cable core to termination Strain relief + IP seal Common Gland Materials Material Best For Nylon (polyamide)General indoor/outdoor use, cost-effective, good chemical resistance Brass (plated)Higher mechanical strength, better earth continuity on armoured cable Stainless steelCorrosive, marine, washdown or high-temperature environments Four Things to Confirm Before You Order 1 Thread Type Matching the Enclosure Entry Metric (M16, M20, M25, M32...), NPT (American tapered thread), and PG (an older European standard still common on legacy equipment) are not interchangeable, even when a thread "almost" seems to fit. Forcing an NPT gland into a metric entry, or vice versa, cross-threads the enclosure and destroys the seal even before the gland is fully tightened. Confirm the enclosure's thread standard first — it's stamped on most enclosures near the entry, or specified on the enclosure's own datasheet. 2 Clamping Range Matching the Actual Cable OD Every gland has a stated minimum and maximum cable outer diameter it can seal effectively — sizing on the actual measured cable OD, not the nominal size printed on the cable's own datasheet, since real-world tolerances vary between manufacturers and cable types. A gland clamped at the very edge of its range rarely seals as reliably as one sized comfortably within it. 3 Armoured vs Unarmoured Construction A standard unarmoured gland only clamps the cable's outer sheath and has no provision for the steel wire armour on SWA cable — using one on armoured cable leaves the armour loose inside the gland with no proper earth continuity path, which is a real fault-clearance and safety issue, not just a mechanical weak point. Armoured cable needs a gland specifically built with an inner cone and armour clamping ring designed for that purpose. 4 IP Rating Matching the Enclosure and Environment A gland's IP rating should match or exceed the enclosure it's fitted to — an IP68-rated enclosure fitted with an IP66 gland only achieves IP66 overall at that entry point. Outdoor, washdown, or submerged installations need the gland rating confirmed against the actual worst-case exposure the cable entry will see, not just the general area classification. Frequently Asked Questions Can I use a reducer or adaptor to fit a gland with the wrong thread type? Thread adaptors exist and can work as a short-term fix, but each additional joint is another potential leak path and reduces the overall assembly's effective IP rating to whatever the weakest joint achieves. Specifying the correct thread from the start is always the more reliable option. Do I need a separate earth tag if the gland already terminates the armour? Depends on the design and site standard — many armoured gland kits include a separate earth tag as an additional bonding point back to the earthing system, on top of the gland's own armour clamp, particularly where local wiring regulations or the enclosure design call for a dedicated earth conductor termination. What's the risk of over-tightening a gland? Over-tightening can crush or damage the cable's outer sheath, and on some designs can distort the sealing ring enough to actually reduce sealing e…