Views: 0 Author: Site Editor Publish Time: 2026-04-14 Origin: Site
A common challenge in compressed air systems is the need to stock multiple types of threaded fittings for different international thread standards. But the versatile Uni‑thread (also called Uni‑Fit) integrated into the SMC KQ2 Series of one‑touch fittings changes the game completely. This article takes an in‑depth look at the technology, benefits, specifications and real‑world applications of the KQ2 Series – the new generation of general‑purpose pneumatic fittings that streamline inventory, speed up assembly, and reduce costs.
Pneumatic systems around the world rely on a confusing mix of thread standards. British Standard Pipe comes in parallel (G, also called PF) and taper (Rc, also called PT) versions; the US standard NPT and NPTF are common in North America; and metric M threads are widely used across Europe and Asia.
In the past, engineers had to stock fittings for each thread type separately, occupying warehouse space and tying up capital. Worse still, cross‑threading or mismatched seals often led to leaks, system downtime, and increased maintenance costs. The KQ2 Series solves this problem at its core.
The KQ2 Series uses a patented Uni‑thread (Uni‑Fit) design that is compatible with NPT, NPTF, Rc(PT), and G(PF) female threads. A single Uni‑thread fitting therefore works with multiple international standards, allowing users to stock only one type of fitting instead of several.
The secret lies in a specially designed NBR laminated stainless steel gasket that seals against the standard 45° chamfer of the female thread Because the seal relies on a gasket and not on the thread itself, the risk of cross‑threading is dramatically reduced, and the fitting can be installed more quickly and consistently.
KQ2 Uni‑thread fittings need only hand tightening followed by a final snug of a wrench to achieve a reliable seal – requiring roughly one‑third the time of conventional fittings. According to independent tests, assembly times can be cut by around 75%, freeing maintenance engineers to focus on more critical tasks.
Unlike fittings that rely on PTFE tape or liquid sealants – which must be reapplied after each disconnection – the KQ2 gasket seal is fully reusable many times without performance loss. This design also minimises the risk of thread‑sealant fragments entering the compressed air system, an important consideration in clean environments such as pharmaceutical or food processing lines.
The KQ2 Series is significantly lighter than older models. Compared to previous generations, the new fittings achieve up to a 23% reduction in width, up to a 24% reduction in height, and an overall weight reduction of 57% – ideal for mobile equipment and weight‑sensitive applications.
The release collar has been redesigned to require up to 30% less force for tube insertion and 20% less resistance for tube removal. The collet also prevents the stainless‑steel chuck from biting too deeply into the tubing, extending tube life and making re‑piping easier.
The KQ2 family includes an impressive 51 body types (straight connectors, elbows, female elbows, bulkhead unions, Y‑joints, reducers, plugs and many others). Each model is available with metric or inch‑size ports and a variety of thread options:
Metric threads: M3, M5, M6
R/Rc (BSPT, PT) taper threads: 1/8″, 1/4″, 3/8″, 1/2″
G (BSPP, PF) parallel threads: 1/8″, 1/4″, 3/8″, 1/2″
NPT threads: 10‑32UNF, 1/16″, 1/8″, 1/4″, 3/8″, 1/2″
Uni (Universal) threads: 1/8″, 1/4″, 3/8″, 1/2″
The fittings accept tubing outer diameters from 2 mm to 16 mm (metric) or from 1/8″ to 1/2″ (inch), and are compatible with nylon, soft nylon and polyurethane (PU) tubes.
Parameter | Value |
Usable fluids | Air, general‑purpose water |
Operating pressure range | –100 kPa (vacuum) to 1 MPa |
Proof pressure (23°C) | 3 MPa |
Fluid temperature (air) | –5°C to +60°C |
Fluid temperature (water) | 0°C to +40°C (no freezing) |
Thread material / surface treatment | Brass (no plating) or electroless nickel‑plated brass |
Seal material | NBR (nitrile rubber) |
Body material | PBT (polybutylene terephthalate) + C3604 brass |
Chuck & guide | SUS304 stainless steel |
Release button | Oval or round shape |
The KQ2 Series operates reliably from vacuum conditions down to –100 kPa up to a maximum working pressure of 1 MPa, making it suitable for both vacuum handling systems and standard compressed air lines.
For water applications, the temperature range is 0°C to +40°C, provided the system is not subject to freezing.
The flexibility and reliability of the KQ2 Series have made it the choice for a wide range of industrial sectors, including automotive, electronics, pharmaceuticals, petrochemicals, steel, textiles, and mining.
Automotive: Used in paint‑shop air compressors to ensure consistent spray‑coating quality.
Electronics & Pharmaceuticals: The contamination‑free gasket seal is ideal for clean environments where thread‑sealant debris cannot be tolerated.
Steel & Mining: The robust brass/stainless steel construction and wide temperature tolerance perform reliably under demanding conditions.
For Uni‑thread fittings, a gasket seal is used; for other thread types (M, R, Rc, NPT) a pre‑applied sealant is available. Both options provide leak‑free connections across the full pressure range.
The 51 body types include all common configurations: male connectors, female connectors, elbow fittings, bulkhead unions, Y‑joints, T‑joints, reducer nipples, plugs, branch connectors and many more. This comprehensive selection allows designers to configure any pneumatic circuit with a single fitting family.
SMC provides full engineering support for the KQ2 Series through its CADENAS 2D/3D CAD system, which allows engineers to output full‑part‑number CAD data in a variety of formats – dramatically speeding up design time and reducing errors.
The SMC KQ2 Series one‑touch fittings with Uni‑thread technology solve one of the oldest problems in pneumatic system design – the need to manage multiple incompatible thread standards. By allowing a single fitting to work with NPT, NPTF, Rc(PT) and G(PF) threads, the KQ2 Series:
Reduces inventory – only one thread type needs to be stocked, freeing up capital and warehouse space.
Saves installation time – up to 75% faster assembly.
Lowers costs – fittings are reusable and eliminate the need for sealants or PTFE tape.
Improves reliability – gasket seal prevents cross‑threading and contamination.
Saves space and weight – up to 57% lighter and 24% shorter than previous models.
Offers maximum flexibility – 51 body types, 8 thread systems, and tube diameters from 2 mm to 16 mm.
For full specifications visit www.waalpc.com.
