Blind Plugs Selection Guide
A blind plug closes a gland hole; polyamide and nickel-plated brass types exist, and the plug must match the hole's thread system (metric, PG) and size.
This guide explains what to look at when choosing products in the Blind Plugs category.
Blind plug types
- Polyamide blind plugs: gray or black polyamide plugs; Ortaç models come in metric and PG sizes, Gwest and Isıso models in PG sizes. They are used in plastic enclosures and junction boxes, alongside polyamide glands.
- Nickel-plated brass blind plugs: nickel-plated brass Ortaç plugs; the manufacturer data states an NBR O-ring, IP68 and screwdriver mounting. They are used in metal enclosures and at entries with brass glands.
Closing the cable opening of a gland that is left in place is a separate job; for that, see the sealing plugs in the Gland Plugs category. Those parts are named with a dual size such as PG 9 / M 16 and fit the gland body, not a threaded hole.
How to choose a blind plug from the hole size
A blind plug must have the same thread system and the same size as the hole it will close. The marking on a gland removed from the hole gives the size. If there is no marking, measure the hole: in the mounting tables of gland manufacturers, the hole diameter is 20.3 mm for M 20x1.5, 21.0 mm for PG 13.5 and 23.0 mm for PG 16; because close diameters correspond to different sizes, choosing by eye is misleading. On Isıso product cards this value is written as the mounting diameter.
If the hole is not threaded, the blind plug is tightened from behind with a lock nut; nuts are listed separately and are selected in the same thread system and the same size as the plug. The thread of a blind plug is short: on an Ortaç polyamide plug for M 20x1.5, the thread length is 7 mm and the head diameter is 24 mm. The sum of the wall thickness and the nut height must fit within this length, and the head must also cover the hole together with its surroundings.
O-ring and IP rating
The degree of protection of a blind plug depends on the seal under the head seating on the enclosure surface. On an Ortaç polyamide blind plug the O-ring is optional; the manufacturer gives IP54 without the O-ring and IP68 with the O-ring. According to IEC 60529, IP54 means protection against harmful dust ingress and against water splashing from any direction, while IP68 means dust-tightness and continuous immersion under conditions defined by the manufacturer. In an enclosure with a high IP rating, confirm before ordering whether the O-ring comes with the product; if it is missing, add an O-ring that matches the thread size of the plug from the Gland O-Ring Gaskets category.
The difference between polyamide and nickel-plated brass blind plugs
A polyamide plug is insulating and does not corrode; Ortaç gives the continuous operating temperature of its PA6 plugs as -20 °C to +100 °C and offers UV resistance on request. A nickel-plated brass plug is more resistant to impact and clamping force and closes the hole in a metal enclosure with a conductive part; for this reason a metal plug is chosen in EMC enclosures where shielding continuity is required. In most applications, the blind plug is taken in the same material as the cable glands on the enclosure.
Brands in this category
- Ortaç: polyamide and nickel-plated brass blind plugs, in metric and PG sizes.
- Gwest: polyamide blind plugs with GW codes; KG at the end of the code indicates the gray model, KS the black model.
- Isıso: PG-thread polyamide blind plugs; models with KTG codes are gray, models with KTS codes are black.
Order notes
Products are listed by the piece; the "(50 pcs/kutu)" notation in a product name is the quantity per box, so check the pack requirement on the product card. For products listed with a lead time, the delivery time is confirmed before ordering. If the same enclosure also needs a nut and an O-ring, choose all three together in the same thread size.
Comparison and selection table
| Selection Criterion | Metric Thread Blind Plug (M12 – M63) | PG Thread Blind Plug (PG7 – PG48) | Polyamide (PA6) vs Nickel-Plated Brass Plug |
|---|---|---|---|
| Thread Standard | EN 60423 Metric (M12, M16, M20, M25, M32, M40, M50, M63) | DIN 40430 PG (PG7, PG9, PG11, PG13.5, PG16, PG21, PG29) | Available in both Metric and PG threads |
| Ingress Protection | IP54 (unsealed) or IP68 (with O-ring gasket) | IP54 / IP68 (paired with locknut & sealing washer) | Plastic: chemical/corrosion resistant; Brass: heavy-duty |
| Drive Style | Slotted screwdriver head, hex socket or hex head | Slotted dome head or wrench flats | Match material to enclosure (polycarbonate vs steel) |
| Typical Application | Sealing spare knockouts on modern enclosures & boxes | Closing unused PG entries on legacy panels & motors | Maintaining IP65/IP68 cabinet integrity on spare holes |
Frequently asked questions
How do you tell which size of blind plug an empty hole needs?
The marking such as M 20 or PG 16 on a gland removed from the hole gives the size. If there is no marking, measure the hole diameter with a caliper: in the mounting tables of gland manufacturers, the hole diameter is 20.3 mm for M 20x1.5, 21.0 mm for PG 13.5 and 23.0 mm for PG 16. The number in a PG size is not millimeters; the outer diameter of a PG 16 thread is 22.5 mm. The blind plug is chosen to match this size exactly; a close diameter in a different system will not seat on the thread.
Does the IP rating change if a blind plug is fitted without an O-ring?
Yes. Sealing is provided by the seal between the head of the plug and the enclosure surface. For its polyamide blind plugs, Ortaç gives IP54 without the O-ring and IP68 with the O-ring, and offers the O-ring as an option. When closing empty holes in an enclosure with a high protection class, check that the O-ring is fitted and that the surface is flat and clean; otherwise the degree of protection of the enclosure drops at this entry.
How is a blind plug fixed in an unthreaded sheet metal hole?
In holes that are not threaded (plain), the blind plug is passed through from the front and tightened from behind with a lock nut of the same thread size. Nuts are listed separately in polyamide and nickel-plated brass; the thread system and size of the plug and the nut must be the same. Because the thread length of the plug is short, check from the manufacturer's dimension table that the sum of the sheet thickness and the nut height fits within this length.
Are a blind plug and a gland plug the same product?
No. A blind plug closes a threaded hole from which a gland was removed or in which none was ever fitted, and has the same metric or PG thread as the gland. A gland plug, on the other hand, is a sealing plug fitted into the cable entry of a gland that is left in place, and it is named with a dual size such as PG 9 / M 16 according to the gland body it fits. Decide which one you need according to whether a gland will remain in the hole.
Can a polyamide blind plug be used in a metal enclosure?
It fits into a hole with the same thread and closes the entry with its seal; in many sheet metal enclosures, polyamide blind plugs are used together with polyamide glands. A metal plug is preferred where impact and vibration are high and in EMC applications where the shielding integrity of the enclosure must be preserved. If the ambient temperature is outside the continuous operating range given by the manufacturer for polyamide, a metal plug should be considered.