Cable Glands: Threads, IP Ratings and Materials — Choosing the Right Cable Entry

A cable gland is the point where your cable meets the enclosure — and the point where most ingress failures begin. The gland has three jobs: hold the cable against pull-out, seal the entry against dust and water, and protect the cable from chafing on the knockout edge. Get the thread, the seal range or the material wrong and one of those three jobs fails, usually months after commissioning when nobody is watching.

What a gland actually seals

The seal is made in two places. The outer seal — a compression ring squeezed by the cap nut onto the cable's outer sheath — keeps water from tracking along the cable into the enclosure. The entry seal — the threaded body against the enclosure wall, usually with a flat gasket or an O-ring — keeps water out at the knockout. Both must be specified: a gland rated IP68 still leaks if the enclosure thread is damaged or the gasket is missing.

Thread systems: metric, PG and NPT

Three thread families dominate. Metric (M12 to M63, and the MG nylon series) is the modern default and the one most enclosures are tapped for. PG (PG7 to PG48) is the older German dimension still found on legacy panels and on plenty of installed equipment — a PG16 gland will not thread into an M20 hole, and forcing it destroys both. NPT is the tapered American thread used in conduit systems. Before ordering, measure the enclosure's existing thread or read its drawing; matching the gland to the hole is the first decision, not the last.

IP ratings: what IP68 really means

IP68 means dust-tight and protected against continuous immersion under conditions the manufacturer specifies — depth and duration are part of the rating, not implied by it. IP66 covers powerful jets; IP67 covers temporary immersion. For buried pits, washdown areas, marine decks and outdoor junction boxes that can flood, IP68 is the correct call. For a dry indoor cabinet, IP68 is money spent on protection you will never use — IP54 or IP55 is usually enough.

Materials: nylon, brass, stainless

Nylon and PVC glands — like our MG series, RoHS-certified — are the workhorse for indoor and sheltered outdoor duty: light, corrosion-proof, non-conductive and cheap. Brass, nickel-plated brass and stainless steel earn their place where there is vibration, UV exposure, chemical spray, or a requirement for continuity of the gland body to earth. Match the material to the environment, not to the price list.

The seal range must match your cable, not your gland size

Every gland size covers a clamping range — for example 5-10 mm of cable outer diameter. A 10 mm gland body does not seal a 4 mm cable; the compression ring simply never touches it. Read the cable's actual OD off its datasheet or calipers, then pick the gland whose range contains it, ideally mid-range so the ring has travel in both directions.

Specification checklist

• Thread type and size matched to the enclosure knockout (metric / PG / NPT)
• IP rating matched to the environment — IP68 for immersion and flooding
• Seal clamping range contains the cable's real outer diameter
• Body material matched to UV, chemical and vibration exposure
• Locknut and gasket included for the entry seal
• Certification required by the market (RoHS, CE as applicable)

Frequently asked questions

Can I use a PG gland in a metric hole with an adapter?

Thread adapters exist and are legitimate for legacy maintenance, but each adapter adds a sealing interface. For new builds, tap or specify one thread family throughout.

Does an IP68 gland make the enclosure IP68?

No. The enclosure's rating is set by its weakest point — lid gasket, drains, other entries. The gland only guarantees its own entry.