Description

Brass Brake Pipe Union M12 x 1mm Male for 1/4″ Pipe

Solid brass male brake pipe union (male tube nut) with an M12 x 1mm external thread, made for 1/4″ (6.35mm) brake and clutch pipe. Screws into M12 x 1 female ports such as master cylinders and valves. Supplied by EMS Spares, Leicester – over 30 years in automotive components.

Specification

* Reference numbers are for identification and cross-reference only. EMS Spares is an independent UK supplier and has no connection with the owners of these part numbers. 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: M12 x 1 is the larger metric brake thread (12mm across the male thread) – do not confuse it with M12 x 1.25 or 1/2″ x 20 UNF, which look similar. Measure the male thread and check the pitch with a thread gauge. Never force a fitting.

Step 2 – male or female?

• Male union (this part): thread on the outside – screws into a threaded hole (master cylinder, wheel cylinder, caliper, T-piece, brake valve).
• Female union: thread on the inside – screws onto a male port, such as the end of many flexible brake hoses. For 3/16″ pipe in the same thread see our EMS-A9.

Step 3 – pipe size and material

For 1/4″ (6.35mm) outside-diameter pipe – larger brake and clutch lines, often from the master cylinder. Suits copper-nickel (Kunifer), copper and steel pipe. Copy the flare on your old 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 port it screws into.
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 12.7mm (1/2″) split / flare nut spanner, not an open-ended spanner, so the brass hex is not rounded.
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 a pack of 2 unions.

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

3/16″ or 1/4″ pipe? This union is for 1/4″ (6.35mm) pipe. For 3/16″ pipe in M12 x 1 see EMS-A9.

Which spanner do I need? The hex is 12.7mm A/F – a 1/2″ 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 fitting before you order.