A brand new VFD, installed in a humid facility in Johor, has just failed due to water ingress. The culprit? A single M20 cable gland selected outside the stated clamping range, which compromised the gland’s IP rating and created a leak path at the enclosure. This wasn’t bad luck; it was an avoidable failure caused by guesswork.
When it comes to protecting your critical equipment, close isn’t good enough. This guide replaces ambiguous charts with a simple, three-step visual method, empowering you to select the correct SKINTOP® gland for a secure, reliable seal every time.
The SKINTOP® Sizing Chart: Your Quick Reference
Stop searching through confusing tables. Here is a clear, visual chart mapping the most common SKINTOP® ST‑M metric cable gland sizes to their exact clamping ranges.
| SKINTOP® Size | Clamping Range (Outer Diameter) |
| M12 × 1.5 | 3.5 – 7 mm |
| M16 × 1.5 | 4 – 10 mm |
| M20 × 1.5 | 6 – 13 mm |
| M25 × 1.5 | 8 – 17 mm |
| M32 × 1.5 | 9 – 21 mm |
| M40 × 1.5 | 16 – 28 mm¹ |
| M50 × 1.5 | 27 – 34 mm |
| M63 × 1.5 | 34 – 45 mm |
Source: LAPP datasheets SKINTOP® ST-M / STR-M (DB53111000EN).
Why Correct Sizing is Non‑Negotiable
Choosing the right size isn’t just about fitting a cable through a hole. It’s about ensuring three pillars of a secure connection in demanding industrial environments.
IP Rating Integrity. A correctly sized gland seals against the cable jacket, achieving its specified IP68 (5 bar/30 min) and/or IP69 rating. In high humidity, even a tiny gap can allow moist air to enter an enclosure, leading to condensation and damage to sensitive electronics.
Reliable Strain Relief. The gland must grip firmly so pulling forces from vibration or movement are absorbed by the gland—not the terminals. An oversized gland won’t grip properly, causing intermittent faults and downtime.
EMC Shielding Continuity. For shielded cables, use an EMC gland such as SKINTOP® MS‑M BRUSH, which provides 360° brush contact for a low‑resistance shield connection. Without it, the shield can behave like an antenna and invite noise into your system.
The 3‑Step Sizing Method: How to Choose a Cable Gland
Get it right every time with this simple process.
Step 1: Measure Your Cable’s Outer Diameter (OD).
Use a digital caliper for an accurate OD. Don’t rely on nominal datasheet values alone—tolerances vary by make and batch.
Step 2: Match to the SKINTOP® Clamping Range.
With your OD in hand, use the chart above. Choose the SKINTOP® size where your OD falls comfortably inside the minimum and maximum range—not at the edges—to ensure a secure seal and strain relief.
Step 3: Verify the Enclosure Thread.
Confirm the mounting hole is metric (M)—don’t mix with legacy PG threads; they are not compatible and won’t seal correctly.
Worked Examples
Example 1: Standard Power Cable on a Conveyor
You’re wiring a conveyor motor with a 4‑core power cable that has a measured OD of 11.8 mm. From the chart, this falls within the 6 – 13 mm range of SKINTOP® ST‑M M20—the correct choice for a secure, IP‑rated connection.
Example 2: High‑Density Sensor Entry on a Packaging Machine
You need to feed 12 small sensor cables into a control panel. Instead of drilling 12 holes, use SKINTOP® MULTI‑M, a round, screw‑in multi‑cable bushing (e.g., M32 variant) that routes multiple unharnessed cables through one entry while maintaining IP68 sealing.
Quick Answers to Common Questions
“What’s the difference between PG and Metric threads?”
PG (Panzergewinde) is a legacy German thread form. Metric (M) is the current international norm. PG and Metric are not compatible—always match gland thread to enclosure thread.
“What happens if I over‑tighten a gland?”
Over‑tightening can deform the sealing insert, damage the cable jacket, and compromise the IP rating. Tighten until the cable is secure; avoid excessive force. SKINTOP®’s integrated self‑locking (ratchet) mechanism provides permanent vibration protection to resist loosening.
“How do I handle high‑vibration environments?”
For machines with significant vibration, ensuring your gland doesn’t loosen is critical. The SKINTOP® series uses a self‑locking mechanism to prevent the cap backing off over time and maintain sealing and strain relief.
“How do I size a gland for a flat cable?”
For flat cables, use a SKINTOP® FLAT gland with a dedicated insert for flat profiles. Multi‑entry systems like SKINTOP® CUBE MULTI are excellent for multiple round cables, not for sealing a single flat cable.
The Bottom Line: Precision Protects Your Investment
In an industrial environment, a cable gland isn’t just a piece of hardware; it’s low‑cost insurance for high‑value equipment. Following these steps ensures a reliable, long‑lasting installation that can withstand demanding factory conditions.
Ready to get the right fit every time? Explore the full range of SKINTOP® cable glands or contact a JJ‑LAPP expert for a personalised recommendation.
Local stock. German quality. Reliably Connecting ASEAN.