Description

Brass Brake Pipe Union 3/8″ UNF x 24 Female for 3/16″ Pipe

Solid brass female brake pipe union (female tube nut) with a 3/8″ x 24 UNF internal thread, made for 3/16″ (4.75mm) brake and clutch pipe. Used where the pipe connects onto a male 3/8″ UNF port – typically flexible brake hoses, some brake valves, inline connectors and adaptors – on classic British cars, kit cars and older vehicles. Supplied by EMS Spares, Leicester – over 30 years in automotive components.

Specification

* Reference numbers are for identification only. All dimensions are approximate.

Buyer’s guide: brake pipe unions explained

What does a brake pipe union do?

A brake pipe union is the threaded nut that holds a flared brake pipe tight against a component or hose. The union itself does not seal; it clamps the flare on the end of the pipe against the seat of the mating part, and that metal-to-metal contact makes the seal. That is why the thread and the flare type must both match.

Step 1 – identify your thread (the most common mistake)

Tip: 3/8″ UNF and M10 x 1 look almost the same and will start to screw together, then bind. Never force a union. Measure the male thread you are screwing onto (9.5mm = 3/8″, 10mm = M10) or use a thread gauge.

Step 2 – male or female?

• Female union (this part): thread on the inside – screws onto a male port, such as the end of many flexible brake hoses.
• Male union: thread on the outside – screws into a threaded hole (master cylinder, wheel cylinder, T-piece). See our EMS-A1 male union.

Step 3 – pipe size and material

For 3/16″ (4.75mm) outside-diameter pipe, the standard UK car brake pipe size. Suits copper-nickel (Kunifer), copper and steel brake pipe.

How to fit – good practice

1. Slide the union onto the pipe the right way round before you make the flare.
2. Make the flare with a proper flaring tool, matching the flare of your old pipe and the part it connects to.
3. Start the union by hand for several turns – it should turn freely. If it binds, stop and check the thread.
4. Tighten with a 9/16″ (14.2mm) split / flare nut spanner, not an open-ended spanner, so the brass hex is not rounded. Hold the hose or mating part with a second spanner so it does not twist.
5. Bleed the brakes, then check every joint for leaks with the pedal pressed hard.

Safety: brakes are a safety-critical system. If you are not confident, have the work done or checked by a qualified mechanic.

Pack sizes

Available as 1, 3, 4, 5, 10 or 20 unions. Larger packs cost less per union.

Delivery

Free UK delivery on every order (including Northern Ireland, Highlands & Islands). Same-day dispatch on orders placed before 10am.

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FAQ

Will this fit copper (Kunifer) pipe? Yes – any 3/16″ (4.75mm) brake pipe: copper-nickel, copper or steel.

Is 3/8″ UNF the same as 3/8″ BSF? No. Same diameter, but BSF has 20 threads per inch and UNF has 24. They are not interchangeable.

Why brass and not steel? Brass does not rust or seize, so the union can be undone again years later without twisting the pipe.

Which spanner do I need? The hex is 14.2mm A/F – a 9/16″ split (flare nut) spanner fits best.

Need help? Message us with your vehicle and the part you are connecting to and we will confirm the right union before you order.