Description
Brass Brake Blanking Cap 3/8″ UNF x 24 Female
Solid brass female blanking cap with a 3/8″ x 24 UNF internal thread, to seal off a male 3/8″ UNF thread – for example a flexible hose end or male union – during repairs, storage or pressure testing. Supplied by EMS Spares, Leicester – over 30 years in automotive components.
Specification
| Thread | 3/8″ x 24 UNF female (24 threads per inch) |
|---|---|
| Type | Female blanking cap |
| Hex / spanner size | N/A |
| Overall length | N/A |
| Material / finish | Solid brass, natural finish – rust resistant, will not seize |
| Weight | 14.1g approx |
| Interchange reference | HU1AB* |
| EMS part number | EMS-A1AB |
* Reference numbers are for identification only. All dimensions are approximate.
Buyer’s guide: brake blanking caps explained
What is a blanking cap?
A blanking cap seals off a brake or clutch port so fluid cannot escape and dirt cannot get in. It is used when a port is not needed (for example an unused outlet on a master cylinder, T-piece or 4-way union), to cap a pipe or hose temporarily while you work, or to pressure-test part of a circuit.
Plug or cap – which do I need?
- Male blanking plug: thread on the outside – screws into a threaded hole (port).
- Female blanking cap: thread on the inside – screws onto a male thread, such as the end of a hose or a male union.
Step 1 – identify your thread
| Thread | Outside diameter (male thread) | Threads | Typically found on |
|---|---|---|---|
| 3/8″ x 24 UNF (this part) | 9.5mm approx | 24 per inch | Most British classics: MG, Triumph, Mini, Austin, Morris, Land Rover Series, Jaguar, kit cars |
| 3/8″ x 20 BSF | 9.5mm approx | 20 per inch | Older British cars (often pre-1960s) |
| M10 x 1mm | 10mm approx | 1mm pitch (about 25 per inch) | Most European and later cars |
| 7/16″ x 20 UNF | 11.1mm approx | 20 per inch | British classics and commercial vehicles, often on 1/4″ pipe circuits |
Tip: 3/8″ UNF and M10 x 1 look almost the same and will start to screw in, then bind. Never force a fitting – forcing the wrong thread damages the port. Measure the male thread diameter or use a thread gauge, or compare against your old part.
How to fit – good practice
- Clean the threads and seat before fitting.
- Start the cap by hand for several turns – it should turn freely.
- Tighten with a correctly sized spanner. Brass is softer than steel – firm, not excessive.
- After any brake work, bleed the system and 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 or 2 caps.
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 it fit an M10 x 1 thread? No. Choose our M10 x 1 female blanking cap (EMS-A2AB).
Need help? Message us with your vehicle and the part you are capping and we will confirm the right cap.
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