Cable Gland Selection Guide: Types, Materials, Sizing & Installation Tips

How a Cable Gland Works

A cable gland is a mechanical device fitted to the entry point where a cable passes through an enclosure, junction box, motor, or piece of equipment. Its purpose is to maintain the integrity of that enclosure while allowing the cable to pass through safely. By tightening the gland, internal components compress around the cable and create both a mechanical hold and a seal.

Core Parts of a Cable Gland

• Gland body — the main structure that carries the thread and houses the sealing components.
• Compression nut / cap — the outer nut that, when tightened, compresses the sealing elements.
• Sealing grommet or ring — an elastomer sleeve that forms the water and dust barrier around the cable.
• Clamping jaws or cone — used in metallic-armoured cable glands to grip the armour and provide earthing continuity.
• Lock nut — secures the gland body to the enclosure wall from the inside.

What Happens When You Tighten the Gland

When the compression nut is turned, the internal taper pushes the sealing ring radially inward. The ring presses against the cable’s outer sheath, closing the gap around it. In armoured cables, this same movement forces the clamping jaws into the armour, creating a strong mechanical anchor and a low-resistance earth path. That is why installing a cable gland correctly matters — an under-tightened gland can let water seep in and offer no strain relief, while an over-tightened one can crush or deform the cable.

How to Choose the Right Cable Gland

There is a simple four-step logic that works for most projects. Start with the cable, then work outward to the enclosure entry.

Step 1: Measure the Cable Diameter Range

Every gland model lists a cable range (for example 10–14 mm). The gland must fit the actual outer diameter of your cable, including any jacket tolerance. If the cable is too thin, the seal cannot compress correctly; if it is too thick, the cable will not pass through the gland body.

Step 2: Match the Thread and Enclosure Hole

Confirm the thread standard and size of the enclosure entry. For a 20 mm metric knock-out, the gland should be M20 with the correct thread length to pass through the wall and allow the lock nut to engage fully.

Step 3: Define the Protection Level

Decide whether you need IP54, IP66, IP67, or IP68 based on where the equipment will be installed. For outdoor, wash-down, or submersion conditions, choose a double-seal type rated at IP66 or higher.

Step 4: Consider the Environment and Certifications

For marine environments, specify A4 stainless steel glands. For explosive atmospheres, choose a certified flameproof gland with the required Ex marking. For VFD installations where electromagnetic interference is a concern, a screened / EMC gland keeps the shield continuity intact.

Installation Best Practices

• Use a proper wrench on the gland body, not on the cable — never pull the cable through a tightened gland.
• Apply the recommended torque; many manufacturers list a value for each gland size.
• Clean the enclosure entry and remove all burrs before fitting the gland.
• For armoured cables, connect the earth tag or armour clamp correctly and test continuity.
• Always keep a stock of spare sealing rings; a damaged grommet cannot be repaired — it must be replaced.

Frequently Asked Questions About Cable Glands

What is the difference between a cable gland and a cable cleat?

A cable gland is fitted at the entry point of an enclosure and seals the opening around a cable. A cable cleat is installed along a cable run, on trays or walls, to hold the cable in position and resist mechanical forces. The gland seals and terminates; the cleat supports and fixes.

Can a cable gland be reused after dismantling?

Yes, but only if all parts are intact and the sealing ring has retained its elasticity. If the grommet is hardened, cracked, or deformed, replace it before reuse. In Ex-rated installations, most safety guides recommend replacing the gland rather than reusing an old one.

How do I know the correct cable gland size?

Measure the actual cable outer diameter first, then confirm the enclosure thread size. Every gland has a specification table showing the recommended cable range for each thread size — use the range, not the thread number, as the primary selection criterion.

When should I choose stainless steel cable glands?

Choose stainless steel when the gland will be exposed to salt, chemicals, wash-down, or any humid environment for long periods. It is slightly more expensive than brass or plastic, but the service life difference in coastal and offshore installations is substantial.