For an existing tapped entry, I choose the matching M or PG thread and check the complete gland assembly. For a new clearance-hole panel, I compare usable thread length, cable fit, seal seating and tool access. The better candidate is the one that satisfies those installation requirements with the simplest suitable arrangement.
Confirm the receiving thread before ordering a replacement. Where the gland and equipment use different systems, a suitable adapter adds another threaded joint and seal to check. On a clearance-hole panel, the locknut and installed layers determine how much usable thread the chosen gland needs.
Key takeaways
- Match the full thread designation to the receiving entry.
- Check pitch, profile, tolerances, mating roles, usable engagement and seal location.
- Check the entry thread separately from cable OD range.
- Select ingress, retention, tightening and any explosion-protection (Ex) functions for the complete installed assembly.
- Select for the actual entry, drawing and complete gland assembly.
Choose M-Type vs. PG-Type threads for the actual entry
A direct thread match uses compatible male and female thread systems, dimensions and limits. I retain a suitable matching PG gland on a confirmed PG tapped entry, and a suitable matching metric gland on a metric entry. This avoids introducing another joint when the selected gland also meets the cable, environmental and electrical requirements.
M identifies a metric thread family. IEC 60423:2007 specifies conduit outside diameters and thread dimensions for conduits and associated fittings. PG, or Panzergewinde, identifies the steel conduit thread addressed by DIN 40430:1971-02. Read the full designation and drawing for the particular interface, including pitch, profile, direction and tolerance or gauging requirements.
For a new panel with a clearance hole, compare both complete mounting arrangements. The hole supplies clearance, while the gland thread mates with its locknut. One candidate may leave enough engagement after the wall and seals; another may need a longer thread. A larger shoulder may improve seating on the intended land yet reduce access to nearby entries. Those are practical differences between selected parts, so compare the drawings on the same panel layout.
M and PG identities before comparison
I put the receiving entry beside both candidate drawings. This makes a difference in profile, usable length or shoulder position visible before parts reach the panel.
| Check | M-Type candidate | PG-Type candidate | Receiving entry or panel |
|---|---|---|---|
| Identity | Full metric designation and drawing | Full PG designation and drawing | Internal thread or clearance-hole definition |
| Thread form and fit | Profile, pitch, direction, tolerance/class | Profile, pitch, direction, tolerance/gauge basis | Matching profile, pitch, female limits, and depth |
| Usable geometry | Full-form male thread after lead-in and runout | Full-form male thread after lead-in and runout | Usable female depth or panel stack |
| Seating and cable | Shoulder, seal location, cable range | Shoulder, seal location, cable range | Land, recess, finish, wall, scheduled cable |
Crest diameter is the diameter across the outer thread peaks. Pitch is the axial spacing between corresponding points on adjacent thread forms. They describe different dimensions: two threads can look similar across their crests but have different pitch or flank geometry. Check the profile, limits, lead-in and seating with the full designation.
The receiving entry controls direct mating
The receiving entry is the equipment feature against which the gland or adapter fits and seals. Identify a tapped hole from the drawing, equipment records or specified inspection. Use trial assembly only after identifying a compatible thread. Forcing a nearly matching thread can damage the entry before the shoulder reaches its intended seat.
At a clearance hole, I compare the hole shape, wall, seal or washer, locknut, usable length and tool access. Check the proposed nut against the gland thread as well as the available space behind the panel. A gland that passes through the hole still needs sufficient full-form thread for that nut after all installed layers are included.
For an unknown entry, use a caliper and pitch gauge to narrow the possibilities. Then apply the specified gauging or inspection method to establish profile, functional fit and usable depth. Check the seating face and any counterbore at the same time; a compatible thread can still place the shoulder or seal in the wrong position.
Two metal fittings and separate tapped openings sit beside a pitch gauge and caliper, showing the parts and tools used to compare thread interfaces.
Locate the seals and cable grip
The entry seal closes the joint between the gland and enclosure. The cable seal closes around the cable jacket. I locate both on the assembly drawing before comparing M and PG variants. The entry may use a shoulder washer, an O-ring in a recess, a bonded seal or another specified arrangement. The intended seating face, surface condition and compression need to suit that arrangement.
Thread pitch affects the mating geometry, while these sealing surfaces control the leakage paths. Cable retention also depends on the gland’s gripping construction and the cable it holds. Choose the complete variant for those duties, then follow its tightening instructions. Increasing turns or tightening force to compensate for a mismatch can damage the thread, seal or cable.
IEC 62444:2010 covers complete glands as supplied. Its scope directly covers IEC 60423 metric entry threads; for other thread types it may be used as a guide. When comparing PG and M products, check the declared functions and tested assembly for each selected variant within that scope.
IEC 60529 classifies enclosure ingress protection (IP). Match the required IP result to the cable, gland, entry seal, accessories and enclosure arrangement. The IEC 60529 selection guide explains how to specify that installed protection.
Installed thread stack and usable engagement
The installed stack is the set of layers and required engagement along the male thread. Usable length excludes lead-in, incomplete runout, damage and shoulder obstruction. Runout is the transition where complete threads end. I include the wall, washer, separate seal, any required earth tag and locknut engagement in the specified order.
For a tapped entry, check usable female depth, bottom clearance, runout, seating face and counterbore. For a clearance hole, check length remaining for the locknut. With an adapter, verify each side separately, then the combined projection and both seals.
The calculator subtracts the required stack from usable male thread length. Enter each installed layer once; a combined sealing washer should not be counted again as a separate seal. Use compressed dimensions where the selected instructions require them. The result helps identify a length conflict before assembly.
Compare two hypothetical thread lengths on one panel
For this hypothetical example, I use a 5 mm panel, a 1 mm washer, a separate 1 mm installed seal and 4 mm of required locknut engagement. These are illustrative inputs, not product dimensions or an engagement rule. Adding the four dimensions gives an 11 mm required stack.
I found a length conflict when I compared two hypothetical candidates on that stack: 15 mm of usable male thread leaves 4 mm reserve, while 10 mm falls short by 1 mm. Both could pass through the same clearance hole. Only the longer candidate meets this assumed axial requirement, so hole clearance alone would miss the problem.
I would next compare the longer candidate’s thread fit, shoulder seating, cable range and tool access. An earth tag or a different seal arrangement changes the installed stack, so include that change before choosing the part. The example favors a usable length for one panel; the same calculation applies to either a metric or a PG candidate.
In this example, and . The symbols denote panel, washer and separate-seal thicknesses, required nut engagement and usable male length, respectively; all are in millimetres. The reserve is a geometric check, with tolerances and specified compression still to be applied.
Is cable diameter range determined by the entry thread?
The cable range belongs to the selected gland’s sealing and gripping elements. The entry thread connects the body to the equipment or locknut. Two M and PG variants may accept the same cable outside diameter (OD), while two glands with the same entry designation may use different inserts and accept different cables.
Check cable construction, shape, OD tolerance and every layer to be sealed or retained against the selected gland variant. The entry bore or adapter must also leave clearance for the cable and internal parts.
The M20 designation breakdown explains why a metric thread label does not define cable capacity. Use the complete cable gland guide when the open question is gland function rather than thread-system preference.
Does one thread system install faster or last longer?
For installation time, compare the actual operations: aligning the gland, reaching the nut, holding the body, tightening the closure and inspecting the seals. A direct matching entry may remove an adapter operation. On another panel, a longer thread or better wrench access may reduce assembly difficulty. I also compare materials, loads, vibration, temperature, corrosion, motion and seal maintenance for service behavior.
Use the tightening and inspection instructions for the selected model and mounting arrangement. The installation do’s and don’ts guide organizes preparation, assembly, verification and rework from those instructions.
Specify the protective bond and electromagnetic compatibility (EMC) screen path where required, including the contact surfaces and any accessories. For hazardous areas, match the installed protection concept, group, gas or dust scope, ambient range and certificate conditions to the equipment. Include any adapter in that review.
Thread-profile, pitch, tolerance, and engagement checks
Check thread identity, functional fit and usable engagement. Match the designation to its profile and pitch, then apply the specified tolerance limits and gauging method. NIST’s paper on pitch-diameter measurement for threaded gauges identifies the pitch-diameter cylinder as the reference datum and explains the associated measurement complexity. A caliper measurement across crests and a pitch-gauge reading are useful identification inputs; use the required functional inspection for the final fit.
Measure complete threads separately from lead-in and runout. At a tapped entry, compare usable female depth with male full-form length and seating position. At a clearance hole, subtract wall, washer, seal and required locknut engagement from usable male length. Record the seating position with the usable length so the gland can reach its intended seal without bottoming out or running into incomplete threads.
Final M-versus-PG decision
These conditions show the available choices for retrofit or new work:
| Condition | Available choice | What still needs to fit |
|---|---|---|
| Tapped entry matches one complete candidate | Use the matching system | Profile, pitch, tolerance, engagement, land and seal |
| Clearance-hole panel supports both candidates | Compare M and PG for that panel | Stack, cable fit, seal, access and required functions |
| Systems differ but an exact adapter suits both sides | Adapter or redesign | Both threads, engagement, joints, seals and material pairing |
| Fit, stack, cable, environment, electrical or Ex requirement conflicts | Change the component or entry | The specific incompatible interface or duty |
| Designation, limit, usable depth or seal method is unknown | Establish compatibility before choosing | Authoritative thread and mounting information |
The thread conversion guide covers identifying NPT, PG and metric systems and qualifying cross-system adapters. Here I use fully specified M and PG candidates to decide one application.
I compare an adapter’s equipment side and gland side as two complete interfaces. Each needs the matching thread, usable engagement and intended sealing arrangement. Then check the combined projection, cable passage and wrench space. The added hardware also needs to suit the materials, exposure and electrical or hazardous-area requirements.
Conclusion
For a tapped entry, I start with the confirmed female thread and select a matching gland that meets the cable and service requirements. For a clearance-hole panel, I compare the complete M and PG stacks, including usable length, seal seating, locknut access and the cable route.
The practical advantage comes from the selected assembly: enough full-form engagement, the correct seals and a workable installation. If an adapter is needed, check both joints and the extra projection before committing to the layout. Those checks turn a broad M-versus-PG question into a clear choice for the actual panel.
M-Type vs. PG-Type thread FAQs
Is an M-threaded cable gland always better than a PG-threaded gland?
Choose the thread that matches the entry and the gland that fits the cable, seals and installed stack. A confirmed PG tapped entry often makes a matching PG gland the simpler direct arrangement. On a new clearance-hole panel, compare the complete mounting options and available thread length.
Can an M gland be fitted into a PG entry if the diameters look close?
Identify the full thread system, pitch, profile and fit before assembly. M and PG are different mating systems; use a suitable adapter or change the entry when the gland and equipment differ. Check each adapter interface for usable engagement and its specified seal.
Does thread pitch determine the cable entry’s IP rating?
Specify IP protection for the complete enclosure and cable-entry arrangement. Check the gland, cable jacket, entry seal, accessories and installation against the tested configuration. Pitch identifies part of the mating thread; the sealing arrangement controls the relevant leakage paths.
Can PG and M glands cover the same cable diameter range?
They can, but the entry designation does not decide that range. Verify the exact gland variant’s cable sealing and clamping range against the cable construction and manufacturing OD limits. Also check that the entry bore, adapter, and installed parts do not interfere with the cable path.
Sources and technical references
- DIN 40430:1971-02 — Steel Conduit Thread; Dimensions, accessed 2026-10-28.
- IEC 60423:2007 — Conduit systems for cable management: outside diameters and threads, accessed 2026-10-28.
- IEC 62444:2010 — Cable glands for electrical installations, accessed 2026-10-28.
- IEC 60529 — Degrees of protection provided by enclosures, accessed 2026-10-28.
- NIST — Pitch Diameter Measurement of Threaded Gages Using the CMM, accessed 2026-10-28.