BSP and NPT Won't Thread Together
BSP (British Standard Pipe) uses a 55° Whitworth thread form. NPT (National Pipe Taper) uses a 60° American National thread. The thread angle and form are different — in most sizes they will not engage correctly, and where they appear to thread in, the seal will leak under pressure.
The most common situation: UK or European equipment has BSP ports on the pump, manifold or valve body. A replacement instrument, pressure gauge or pump sourced from North America has NPT threads. Or vice versa: American machinery being integrated into UK or Australian pipework. You need an adapter with the correct thread form on each end — not a standard catalogue part, because the exact size combination or form factor you need often isn't stocked.
| Property | BSP (BSPP) | NPT |
|---|---|---|
| Thread angle | 55° Whitworth | 60° American National |
| Thread form | Parallel (BSPP) or tapered (BSPT) | Tapered — 1/16″ per inch |
| Seal method | BSPP: face washer or O-ring. BSPT: thread engagement + PTFE | Thread engagement + PTFE tape or thread sealant |
| Standard | BS EN ISO 228 (BSPP), BS 21 (BSPT) | ASME B1.20.1 |
| TPI at 1/2″ | 14 | 14 |
| Typical use | UK, Europe, Australia, Asia | USA, Canada |
Adapter Types We Machine
We machine to order — not from stock. If the combination or form factor you need doesn't exist in a catalogue, that is exactly the situation we handle.
| Form | Description | Common use case |
|---|---|---|
| Hex nipple (M × M) | BSP male one end, NPT male the other | Connecting BSP female port to NPT female port |
| Reducing bush (F × M) | BSP female one end, NPT male the other — or reverse | Adapting a NPT instrument into a BSP port |
| Street elbow (90°) | BSP × NPT with 90° offset | Where a straight adapter won't clear |
| Tee | Three-port with mixed BSP/NPT threads | Branching a BSP line into two NPT instruments |
| Bulkhead | For panel mounting — hex shoulder, locknut | Passing a line through a panel with mixed threads |
| Reducing | Different nominal sizes on each end (e.g. 3/4″ BSP × 1/2″ NPT) | Any size mismatch between BSP and NPT ports |
BSPP or BSPT — Which Do You Have?
Both are called "BSP" which causes frequent ordering errors. The difference matters: BSPP is a parallel thread that seals on a flat face (using a sealing washer or O-ring in a recess). BSPT is a tapered thread that seals by thread engagement, like NPT. You can identify BSPP by the chamfered or recessed face on the female fitting. See our full guide: BSPP vs BSPT — What Is the Difference?
When ordering, specify which BSP type you have on each port. If you are not sure, send us the fitting and we will measure it.
Common BSP to NPT Size Combinations
The table below covers the most frequently requested combinations. We machine any size and any mix — if yours is not listed, just state both thread designations.
| BSP end | NPT end | Typical application |
|---|---|---|
| 1/8″ BSPP M | 1/8″ NPT M | Pressure gauge port, instrument tapping |
| 1/4″ BSPP M | 1/4″ NPT M | Air line instruments, flow control valves |
| 1/4″ BSPP F | 1/4″ NPT M | Fitting a NPT-threaded gauge into a BSP manifold port |
| 3/8″ BSPP M | 3/8″ NPT M | Hydraulic sub-plate porting, pneumatic cylinders |
| 1/2″ BSPP M | 1/2″ NPT M | Pump outlet, control valve inlet |
| 1/2″ BSPP F | 1/2″ NPT M | Adapting an NPT pump into a BSP manifold |
| 3/4″ BSPP M | 3/4″ NPT M | High-flow hydraulic lines, larger valve bodies |
| 3/4″ BSPP × 1/2″ NPT | Reducing adapter — size mismatch between BSP and NPT ports | |
| 1″ BSPP M | 1″ NPT M | Manifold ports, high-flow circuits |
| 1/4″ BSPT M | 1/4″ NPT M | Older UK pipework or Asian equipment with BSPT ports |
Material and Pressure
| Material | Working pressure | Suited to |
|---|---|---|
| Brass (CW617N) | Up to ~10 bar | Water, compressed air, low-pressure gas, instrumentation |
| Carbon steel (zinc-plated) | Up to 350 bar (by wall section) | Industrial hydraulics, high-pressure air, general engineering |
| 304 stainless | Up to 250 bar (by wall section) | Food and beverage, mild corrosion resistance |
| 316 stainless | Up to 250 bar (by wall section) | Marine, offshore, chemical duty, corrosive hydraulic fluids |
Pressure-critical note. Hydraulic and pneumatic fittings are safety items. Tell us the working pressure and the system fluid when you enquire and we will confirm the appropriate material and wall section. We do not guess.
Applications
How to Order
Use the form on this page or email [email protected]. Tell us:
- Thread on each end: e.g. 1/2″ BSPP male × 1/2″ NPT male
- Form: straight hex nipple, reducing bush, elbow, tee, etc.
- Material: brass, carbon steel or stainless (304 or 316)
- Working pressure and fluid — so we confirm the right wall section
- Quantity
If you have the old adapter or a fitting to match, send it to us — we measure and reproduce. If the combination is awkward to describe, send a photo. We quote within 24 hours.
Need a hydraulic-rated adapter? See custom hydraulic adapters for JIC, ORFS and SAE ORB types, or general thread adapters for low-pressure applications. Also see our guide: BSPP vs BSPT — what is the difference?
Frequently Asked Questions
BSP uses a 55° Whitworth thread form; NPT uses a 60° American National form. The thread angle differs, so they will not seal correctly even where the nominal size and TPI appear the same. An adapter with BSP on one end and NPT on the other is the correct solution.
BSPP (parallel) seals on a flat face — look for a chamfer or washer recess on the female fitting. BSPT (tapered) seals by thread engagement. In hydraulic and pneumatic systems, BSPP is more common. If you are unsure, send us the fitting and we will identify it. See our full BSPP vs BSPT guide.
Yes — for example 3/4″ BSPP female × 1/2″ NPT male. Any size combination is possible, including very uncommon ones. Just state both thread designations and we will quote it.
Carbon steel (zinc-plated) for most industrial hydraulic applications up to 350 bar. 316 stainless for corrosive fluids, marine or offshore duty. Brass is only suitable for water, air and low-pressure applications — not hydraulics. Tell us the working pressure and fluid and we will advise.
One piece. No tooling charge. A single repair fitting is exactly what we are set up to handle. Larger batches reduce the unit cost, but one piece is always acceptable.
Get a BSP to NPT Adapter Quoted
State both thread ends + material. Engineers reply within 24h.
// Qty & price
1 pc
No MOQ
Prototype or repair
10–50
Setup shared
Price per piece drops
100+
Best rate
All tiers quoted
- →Machined to spec — not sourced from stock
- →CAD drawing saved after first order — reorder any time
or email [email protected]