Ordering the wrong cable gland is one of the most expensive and frustrating mistakes in industrial wiring projects. The component often arrives after weeks of lead time, only to discover that the thread does not fit the enclosure hole or the seal cannot grip the cable properly. Every year, engineers and procurement teams lose time and money on this preventable error because they confuse thread standards, guess sizes from cable gauge, or skip the measurement step entirely. The solution is a structured three-step calculation process based on standardized thread dimensions, not intuition or habit.
1. Understanding the Four Thread Standards
German Standard
PG Threads (Panzergewinde)
Widely used across European industrial equipment. The nominal number does not represent any physical dimension:
PG7 → 12.5 mm OD = M12 × 1.5
PG9 → 15.2 mm OD = M16 × 1.5
PG11 → 18.6 mm OD = M18 × 1.5
Global Default
Metric Threads (M16 × 1.5)
Identified by the letter M plus nominal diameter and pitch — the most common standard in Asia and increasingly in global automation. In the Hoonsun catalog, each PG size maps to a metric equivalent, so one panel design accepts either thread family. Metric glands also offer extended thread length options for thick enclosure walls.
British Standard
G Threads (Whitworth)
Specified by nominal pipe sizes — common in European machinery, pneumatic systems and water handling:
G1/2 → 20.9 mm OD
G3/4 → 26.4 mm OD
G1 → 33.2 mm OD
American Standard
NPT Threads (Tapered)
Used predominantly in North America. Sizes such as NPT1/4, NPT3/8, NPT1/2 use a tapered profile that seals by interference. NPT1/2 measures approximately 20.9–21.2 mm OD depending on the variant. Tapered threads need correct torque and cannot be interchanged with straight PG or metric threads.
2. The Three-Step Size Calculation Process
1
Measure the Finished Cable OD
Use the actual outer diameter of the finished cable — jacket, shielding braid and armor included. Never use conductor cross-section or nominal gauge. Measure at three points with a caliper and average.
2
Match the Gland Cable Range
Pick the variant whose seal range centers on your measurement. A 6 mm cable fits the PG9 standard (4–8 mm); a 5 mm cable fits PG9-(6) (3–6 mm). Near the edge of a range? Choose the adjacent size.
3
Verify Thread & Panel Hole
Confirm the gland thread fits the enclosure opening with correct tolerance, and check thread length against wall thickness: PG9 standard is 8 mm; the extended L12 version provides 12 mm engagement for thick walls.
3. A Practical Sizing Example
Entry 1 — Instrument Cable
A control cabinet with a 6 mm instrument cable and a 5 mm wall panel. Measured OD: 6.0 mm → select PG9 standard (4–8 mm range). The panel hole accepts the 15.2 mm PG9 thread; the 8 mm standard thread length fully engages the 5 mm wall.
Entry 2 — Power Cable
A second entry carries a 9 mm power cable through a 12 mm thick panel. The PG11 gland (6–12 mm range) combined with the extended thread version ensures both a proper seal and full thread engagement.
FAQ
Q: Is PG9 the same as M9?
No. PG9 corresponds to M16 × 1.5 thread with a 15.2 mm outer diameter. The PG number never equals the metric size directly.
Q: How do I choose between PG and metric thread glands?
Match the thread standard of your enclosure hole and regional preference. European equipment commonly uses PG or G, while Asian and American equipment favors metric and NPT respectively.
Q: What happens if the cable diameter falls between two gland sizes?
Select the larger size whose range covers the measurement with margin, then confirm the seal still compresses adequately. When possible, use the variant whose range centers on the actual cable diameter.
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