A hose assembly has three parts that all have to agree with each other: the hose, the tail that goes inside it, and the ferrule that squeezes down over the outside. Get any one of them wrong and the assembly will either leak, blow off under pressure, or fail a pressure test you were counting on passing.
This guide walks through the four decisions in the order you actually have to make them, and flags the mistakes we see most often in enquiries.
The four decisions, in order
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Measure the hose — both diameters, not just one
The inside diameter (ID) sizes the tail. The outside diameter (OD) sizes the ferrule. These are two separate measurements and you need both.
This is the single most common gap in the enquiries we receive. A buyer sends “2 inch hose tail, 50 pieces” and nothing else. But two hoses with the same 2″ bore can have quite different outside diameters depending on wall thickness and reinforcement — and the ferrule has to fit the outside. Without the OD, any ferrule we quote is a guess.
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Choose the thread standard at the other end
The tail has a serrated shank at one end and a thread at the other. The thread has to match whatever it is going into — a pump port, a valve, a coupling.
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Match the ferrule to the hose OD and the tail shank
The ferrule is not a generic sleeve. Its internal diameter, length and wall thickness all have to suit the hose you are crimping onto and the shank profile underneath.
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Decide whether to crimp or clamp
Crimping is permanent and generally handles higher pressure. Bolt clamps are serviceable in the field. Neither is universally better.
Step 2 in detail: thread standards
Three standards cover the overwhelming majority of industrial hose work, and mixing them up is expensive.
| Standard | Designation | Thread form | Seals on |
|---|---|---|---|
| BSPP Parallel | G · ISO 228 | 55° Whitworth | A machined face, using a bonded seal, O-ring or sealing washer. Not on the thread itself. |
| BSPT Taper | R · ISO 7-1 | 55° Whitworth | The thread flanks. Normally needs PTFE tape or thread sealant. |
| NPT Taper | NPT · ASME B1.20.1 | 60° | The thread flanks. Needs sealant. |
In 1/2″ and 3/4″, BSP and NPT happen to share the same 14 threads per inch. A BSP tail will start to turn into an NPT port and it will feel correct for the first turn or two.
It is not correct. The thread forms are 55° and 60°, so the flanks never mate properly. It will not seal, and tightening it damages both parts. If you inherit a fitting and are not certain of its standard, measure the thread form — do not go by whether it starts to thread in.
A practical rule for sourcing: BSP is the default across the UK, Australia, New Zealand, South Africa, India and much of Asia. NPT is the default in North America. If your assembly is going to a mine site in Western Australia, specify BSP unless you have been told otherwise. Sunze supplies BSPP (G) as standard on hose tails, and BSPT or NPT on King Nipples.
Step 3 in detail: which ferrule
Ferrules differ in how they grip and in whether the assembly can be taken apart. The three families we manufacture cover most industrial hose work:
| Type | Construction | Typically used for |
|---|---|---|
| F50 | Plain crimp sleeve | General purpose crimped assemblies where a straightforward, uniform squeeze onto the hose OD is enough. |
| F60 | Slotted ferrule | Hoses where the slots let the ferrule close down further and grip a thicker or softer cover more evenly. |
| F70 | External swage with collar | Heavier duty assemblies where the collar gives a positive stop against the tail and resists pull-off. |
We have deliberately not printed crimp diameters here. The correct finished crimp diameter depends on your specific hose construction and on the machine and die set you are using — it is not a property of the ferrule alone. Use the crimp chart for your machine, or send us the hose specification and we will pair the ferrule to it.
Step 4 in detail: crimp or clamp
Crimping gives a compact, tamper-resistant joint and is normally the right answer for pressure service and for assemblies that will be handled roughly. But it needs a crimping machine, and once it is on, it is on.
Bolt clamps make sense when:
- The assembly has to be made or repaired in the field, without a crimper
- The bore is large — suction and delivery hose in the upper size range is very commonly clamped rather than crimped
- The hose will be re-terminated periodically as the end wears
- The duty is suction or low-to-medium pressure delivery rather than high pressure
Clamp choice then follows the duty: double bolt clamps for general heavy hose, T-bolt clamps where you want even circumferential load on a smaller diameter, interlocking clamps for larger bores, and DIN 2817 safety clamps where a standard is specified — typically chemical transfer and tanker work, where the clamp has to be certified rather than merely adequate.
The mistake that costs the most: mixed metals
A stainless tail with a plain carbon steel ferrule crimped over it, sitting in salt spray, is a galvanic cell. The carbon steel is the anode and it will corrode preferentially — often at the crimp, where you cannot see it. The assembly can look sound from the outside and still be losing its grip.
The rule is simple: keep the tail and the ferrule in the same material family wherever the environment is wet, salty or chemically aggressive. Coastal installations, aquaculture, mine-site brine, wash-down areas and marine deck service all qualify.
| Environment | Sensible pairing | Why |
|---|---|---|
| General industrial, indoor, dry | Carbon steel or plated tail + carbon steel ferrule | Lowest cost, corrosion not a governing factor |
| Agriculture, water transfer, outdoor | Galvanised or 304 tail + matching ferrule | Handles weather and general wet service |
| Coastal, marine, aquaculture, brine | 316 stainless tail + stainless ferrule | Molybdenum in 316 resists chloride pitting; matched metals avoid galvanic attack |
| Chemical transfer | 316 stainless, with the chemical checked against a compatibility chart | Grade alone is not sufficient — the specific medium governs |
For reference, our own standard range runs from carbon steel FDKP and plated FD4 through to SS304 FDKS on King Nipples, and 304, 316 or galvanised carbon steel on BSP hose tails, in sizes from 1/2″ to 12″ (DN15 to DN300).
Before you send an enquiry
If you send these five things, you will get a quotable answer first time instead of three rounds of questions:
- Hose ID and OD — both, in mm or inches
- Thread standard and size at the fitting end (BSPP, BSPT or NPT)
- Material, or the environment if you would rather we recommend one
- Crimped or clamped, and the machine or die set if crimped
- Quantity and destination port — this affects lead time and packing
A photograph of the existing fitting, or a drawing, is worth more than any description. If you have a sample, that is better still — we routinely quote against samples.
Send us the hose specification
We will pair the tail, ferrule and clamp to your hose and come back with a quotation within 24 hours. ISO 9001 CNC manufacturing in Taiwan, OEM and private label welcome.
Request a quotation