SMC KK4S-02MS S Coupler Socket R1/4 Male Thread

A quick-disconnect socket with a built-in check valve

KK4S-02MS is the socket half of an SMC KK series S coupler, size 4 (for 1/4 connections). A coupler lets an air line be connected and disconnected quickly without tools, for example when a tool, a fixture or a test rig is changed. The socket stays on the fixed side of the line and takes the matching plug KK4P-02MS.

The code reads KK (series), 4 (body size for 1/4), S (socket), 02 (R1/4 port size), M (male thread connection) and S (with sealant on the male thread). The socket has a built-in check valve as standard, so air does not escape when the plug is removed, although the catalogue notes that the couplers are not guaranteed for zero leakage.

Technical specifications

The sleeve lock and the check valve

The sleeve is pulled back to connect or disconnect, and it locks in the connected position, which prevents an accidental release when the hose is pulled or vibrates. The KK2 size has no lock mechanism, but this size 4 has it as standard. The catalogue describes the pulling strength of the plugs and sockets as improved.

Because the socket has a check valve, it holds back the air when the plug is out. If the socket is on a branch that must be exhausted, do not rely on it for a leak-tight seal, since the catalogue does not guarantee zero leakage and so it should not be used to hold pressure for a long time.

Selection notes

The effective area of 39 mm2 is the figure for the coupled pair. A coupler adds a restriction to the line, so the flow needed by the machine should be compared with this figure and, if needed, a larger body size should be chosen. The size 6 pair with 1/2 ports has an effective area of 82 mm2, as an example.

A coupler works with a matching plug of the same size and series. The KK series plug and socket must be matched; do not combine with other brands of coupler.

Related SMC products: SMC AN20-02 Resin Silencer R1/4 Male Thread, SMC AS2201F-01-06 Speed Controller 6 mm Tube, R1/8, SMC KQ2H06-01S One-touch Male Connector 6 mm, R1/8, SMC ZH07BS-06-06 Vacuum Ejector Box Type 0.7 mm, 6 mm Tube, SMC ZH10DS-06-06-08 Vacuum Ejector Body Ported 1.0 mm and SMC TU0604BU-20 Polyurethane Tubing 6 mm Blue, 20 m.

Documents and quotation

The SMC KK catalogue PDF below has the how-to-order page, specifications, effective areas and dimension tables. Please confirm body size, thread, connection type and sealant before ordering. Related parts are listed under Automation Accessories. Seven Star LLC is an independent supplier and quotes the exact code on request.

KK4S-02MS Dimensions, Materials & Spare Parts

How the KK4S-02MS Socket Works

SMC describes the KK series as using a unique connection method. It does not use steel balls, so the flow path is not restricted, and the body can be slim while keeping a large effective area. When the plug is pushed in, the PBT chuck grips the plug stem and the manual sleeve locks the connection. At the same time the plug opens the built-in check valve. Because there is no valve spring in the flow path, little effective area is lost. The check valve end is shaped to rectify the flow, and the low-leakage seal uses surface contact. When the sleeve is pulled back and the plug is released, the check valve closes and holds back the supply air.

The sleeve cover, standard on the KK3, KK4 and KK6 sizes, protects the sleeve and absorbs shock when a coupler is dropped. The lock ring is made of shock absorbent PBT for the same reason.

Selection & Ordering Guide

• Body size 4 sockets are offered with R 1/8, R 1/4, R 3/8 and R 1/2 male threads (-01MS to -04MS), Rc female threads, a hose nipple and One-touch tube fittings. KK4S-02MS is the R 1/4 male version.
• Matching plugs: any KK4 plug, for example KK4P-02MS (R 1/4 male) or KK4P-02F (Rc 1/4 female).
• KKH series: SMC also offers the KKH4S-02MS. It has the same effective area, can absorb drop impact equivalent to 0.5 J, and has twice the pulling strength of the earlier models, for portable tools that are often dropped.

Our team can help confirm the correct ordering code for the KK4S-02MS and the matching plug for your hose or tool.

Installation & Maintenance

• Tighten the R 1/4 thread with a spanner on the 19 mm flats. Do not over-tighten, and do not grip the sleeve.
• The thread already has sealant. Clean the female port before fitting so that no chips enter the line.
• Exhaust the pressure before disconnecting where possible, and support the hose so that its weight does not bend the coupler.
• Do not use the coupler with a leak tester or for vacuum retention, because SMC does not guarantee zero leakage.
• Replace a worn sleeve cover with the spare part KK4S-P01.

Typical Applications in Oman & the GCC

Air tool drops in workshops, blow guns, quick-change fixtures, mould and die change on presses, test benches, and general-purpose cooling water lines (5 to 40°C, no freezing) in plants across Oman and the GCC.

Why Source the KK4S-02MS from Seven Star LLC

Seven Star LLC supplies SMC KK and KKH couplers, fittings, tubing and air preparation equipment across Oman and the GCC. Request a quote for sockets and matching plugs, and our team can help confirm the correct ordering code.