Short Answer: Torque Is a Means, Not a Setting

There is no torque value you can memorise and apply to every cable gland, and any page that gives you one number for “a cable gland” is describing one product in one size with one seal compound. Tightening has to achieve three things — compress the seal, clamp the cable, and keep both under vibration — and the force that achieves them changes with the thread size, the seal material and whether the body tightens onto a shoulder or onto the panel.

What you can standardise is the method: tighten until the seal is compressed and the cable will not move, stop before the seal is permanently deformed, and verify the result rather than the tool reading. This guide covers what determines the figure, how to read the figure your supplier gives you, and how to sign off a gland that was tightened by hand.

What Tightening Actually Has to Achieve

Three jobs, done by two different parts of the gland, and they interact.

The conflict is built in. The same tightening force that compresses the insert also deforms the cable and loads the thread. There is a window where all three jobs are satisfied and it is narrower than most fitters assume, especially on small threads where the difference between “sealed” and “stripped” is a fraction of a turn.

Why There Is No Universal Torque Table

Five variables move the correct figure, and only one of them is under the installer’s control.

Because four of those five are fixed by the part and one by the cable, a torque figure only means something when it is stated per size and per seal material. A single number on a catalogue page is not a specification; it is an average of a range the supplier has not disclosed.

Under-Tightening: the Failure That Looks Fine for Months

An under-tightened gland passes a visual inspection, passes a pull test done by hand at commissioning, and fails in service. The seal is in contact but not compressed, so it holds against splash and loses against a pressure differential, thermal movement or a cable that is pulled at an angle.

• Water tracking along the cable — the classic. The insert is touching the jacket but has no radial load, so water enters at the point where the cable bends and travels inside the jacket into the enclosure.
• Cable slip — the cable creeps under its own weight or under repeated movement, and the bend radius that was designed into the entry disappears.
• Gland loosening — the thread was engaged but not loaded, so vibration walks it back out. On a pump or a compressor this can take weeks, which is exactly why it is found on a routine inspection rather than at commissioning.
• Failed IP test — the test that would have caught it is the one most projects skip, because the gland looked right.

Over-Tightening: the Failure That Happens Immediately

Over-tightening is the more destructive of the two and it usually happens for a good reason — the fitter is correcting a leak by adding force. Four things break, in this order.

Past a certain point, more torque makes the seal worse: the elastomer has a fixed volume, so squeezing beyond its elastic limit moves it sideways into the clearance instead of pressing harder on the cable.

How to Read the Torque Figure on a Datasheet

When a supplier does publish a figure, six things have to be pinned down before it can be used. Ask for all six in writing; a figure without them is a number looking for a purpose.

• Which component. Dome nut, body into the enclosure, or locknut. These are three different joints with three different limits.
• Which seal material. A gland supplied with EPDM and the same gland in NBR do not share a figure.
• Which unit and which tool. N·m and lbf·ft are not interchangeable in practice, and a figure quoted for a torque wrench is not usable with a spanner extension.
• Thread condition. Dry, lubricated, or with thread sealant — friction changes the relationship between torque and clamping force, which is the only thing that actually matters.
• Cable position. A figure quoted at the middle of the range is conservative at the top and excessive at the bottom.
• Whether a locknut or threaded boss is assumed. The reaction point changes the load path completely.

Our own datasheets list the dimensional columns per size; where a tightening figure is needed we quote it per size and per seal compound on request rather than publishing a blanket number. That is the honest position for a range that spans M14 to M63 in three body materials.

Tightening Without a Torque Wrench

Most glands in the world are tightened by hand with a spanner. What works is a repeatable method with an observable end point.

1. Hand-tight first, then count. Run the nut down by hand until it touches, then apply a defined fraction of a turn with the spanner — the same fraction for the same size and seal on every gland in the panel. Consistency across a batch is worth more than precision on one.
2. Watch the insert, not the nut. The end point is when the seal stops moving and just starts to resist. Once the rubber has stopped travelling, further turning is load on the thread, not compression on the seal.
3. Test the cable, not the nut. With the gland tightened, try to rotate and pull the cable by hand. Movement means the grip is not there; that is the criterion the fitter can actually judge.
4. Mark and re-check. A paint or marker line across nut and body shows movement at the next inspection without any tool.
5. Build one dummy assembly. On a first batch, tighten one gland onto an offcut of the actual cable until it is clearly over-tightened, then back off. Fitters calibrate to a real destroyed sample faster than to any number.

Les installation guide covers the sequence around this step, and the installation precautions list the handling errors that make a correctly torqued gland leak anyway.

Sequence and Re-Torque

Order matters as much as force. On a single compression gland there is one joint; on a double compression gland the inner seal has to be set before the outer one, because tightening the outer first drags the inner assembly and leaves it under-compressed. That sequence, and why it cannot be reversed, is covered in the single vs double compression comparison.

Re-torque is a separate decision. Elastomers take a permanent set after the first thermal cycles, so a gland that was correct when it was made can be loose a month later — which is why the second visit matters more than the first. Re-check after the first heat cycle on equipment that runs hot, and at the first scheduled maintenance on anything exposed to vibration or weather. Do not re-torque on a schedule for its own sake; re-torque where the joint has a reason to relax.

What a Torque Requirement Should Look Like in a Purchase Order

If the assembly is safety-related, on an Ex installation, or subject to a customer witness test, the requirement belongs in the order rather than in a conversation.

Two cautions. On hazardous area work the tightening specified in the certification documents overrides anything in this article or in a general catalogue, and the thread engagement is part of the certification rather than a workmanship preference. And on stainless steel bodies, thread galling can seize a joint before the correct torque is reached — the answer is a suitable lubricant approved for the environment, not more force.

FAQ

What is the correct tightening torque for a cable gland?

It depends on the size, the seal material and the body material, and it is quoted per size by the supplier. Anyone giving a single figure for all glands is quoting a specific product, not a rule.

Can I tighten a cable gland by hand?

Yes, if the end point is judged from the seal rather than the effort. Hand plus a defined fraction of a turn, checked by trying to move the cable, is more reliable than a torque wrench used without knowing what the figure refers to.

Why does my gland leak after I tightened it more?

Because the seal has probably been extruded. Beyond the correct compression the elastomer moves into the clearance instead of pressing on the cable, and the joint gets worse with every extra turn. Replace the insert rather than adding force.

Do I need to re-torque after installation?

After the first thermal cycle on hot equipment, and at the first service interval on vibrating or weather-exposed installations. Elastomers take a permanent set, so the joint that was correct at assembly can be loose later.

Does the tightening torque change if I use a locknut?

The load path changes, so the figure does. A locknut provides the reaction point instead of a threaded boss, and the panel thickness between them becomes part of the joint.

If you tell us the size, the seal compound and the cable, we will return the tightening figure for that combination along with the dimensional data from the thread size chart and the hole required from the hole size chart. The brass et Nylon ranges have different limits, and the IP rating guide explains what the seal has to achieve once it is tight.