Short answer: a king nipple is a one-piece steel hose fitting with a male pipe thread (NPT or BSPT) on one end and a long serrated hose shank on the other. The shank goes inside the hose and is held there by a bolt clamp, band clamp or crimped ferrule; the thread screws into a pipe, valve, pump or coupling. It is the standard way to put a threaded end on water, agricultural, mining and construction suction and discharge hose from 1/2" up to 12".
1. Other names for the same fitting
Buyers, catalogues and hose shops use several names. They all describe the same part.
| Name | Where you will hear it |
|---|---|
| King nipple | North American distributors and hose shops |
| KC nipple / king combination nipple | Catalogue part descriptions, especially in the US |
| Combination nipple / combination hose nipple | General industrial supply; "combination" because one part combines a pipe thread and a hose shank |
| Hose shank / hose nipple | Plant maintenance and pump rental |
| Hose tail (threaded) | Australia, the UK and Europe, usually with a BSPT thread |
"King" began as a trade name and is now used generically by most manufacturers and distributors, in the same way people say "camlock" for any cam-and-groove coupling.
2. Anatomy: three zones, two dimensions that matter
Thread end
A tapered male pipe thread: NPT for North America, BSPT for most other markets. Because it is tapered, it seals on the thread flanks with tape or paste, not on a gasket.
Body and collar
The section between thread and shank. The collar is the hose stop and the bearing face for the clamp or ferrule.
Serrated shank
The ridged section that goes inside the hose. Its length (K2 on our drawings) is what decides how much grip you get and how wide a clamp or ferrule it can take. Too short a shank for the hose wall and clamp width is a common reason an assembly pulls apart.
3. Sizes and thread data
King nipples are sized by the nominal pipe size of the thread, which also matches the hose ID they are meant for: a 2" king nipple goes into 2" ID hose and screws into a 2" pipe thread. The common range is 1/2" to 12".
The thread itself is not a manufacturer's secret. It is set by the standard, so a 2" NPT king nipple from any reputable maker will engage a 2" NPT port the same way. These are the reference values every NPT king nipple has to meet:
| Size | Pipe OD (in) | NPT TPI | NPT L2 (in) | BSPT TPI |
|---|---|---|---|---|
| 1/2" | 0.840 | 14 | 0.534 | 14 |
| 3/4" | 1.050 | 14 | 0.546 | 14 |
| 1" | 1.315 | 11.5 | 0.683 | 11 |
| 1-1/4" | 1.660 | 11.5 | 0.707 | 11 |
| 1-1/2" | 1.900 | 11.5 | 0.724 | 11 |
| 2" | 2.375 | 11.5 | 0.757 | 11 |
| 2-1/2" | 2.875 | 8 | 1.138 | 11 |
| 3" | 3.500 | 8 | 1.200 | 11 |
| 4" | 4.500 | 8 | 1.300 | 11 |
| 6" | 6.625 | 8 | 1.513 | 11 |
| 8" | 8.625 | 8 | 1.713 | — |
| 10" | 10.750 | 8 | 1.925 | — |
| 12" | 12.750 | 8 | 2.125 | — |
TPI = threads per inch. NPT values from ASME B1.20.1; BSPT pitch from ISO 7-1. L2 is the NPT effective thread length: the length of thread that actually engages and seals, not the total threaded length on the part.
NPT and BSPT do not mix. From 1" up they look close (11.5 vs 11 threads per inch) and will start by hand, then leak or gall. Australian, UK and Middle East pumps and valves are almost always BSP; US equipment is NPT. If you are not sure, count the threads over one inch before you order.
4. Example dimensions: crimp-style KC nipple
Overall length and shank length are where makers differ, and where the fitting has to match the clamp or ferrule you plan to use. As an example, these are the published dimensions of our FDK6N crimp-style nipple, made from seamless steel tube, plated, and paired with the F6040D heavy-duty ferrule:
| Size | NPT part no. | BSP part no. | L overall, mm (in) | K2 shank, mm (in) |
|---|---|---|---|---|
| 1-1/2" | FDK6N015N | FDK6N015B | 100 (3.94) | 70 (2.76) |
| 2" | FDK6N020N | FDK6N020B | 117 (4.61) | 82 (3.23) |
| 3" | FDK6N030N | FDK6N030B | 152 (5.98) | 102 (4.02) |
| 4" | FDK6N040N | FDK6N040B | 181 (7.13) | 104 (4.09) |
| 6" | FDK6N060N | FDK6N060B | 253 (9.96) | 151 (5.94) |
From the Sunze 2026 catalogue. Clamp-style FDKP (plated carbon steel) and FDKS (SS304) king nipples cover 1/2" to 12"; dimensions for those and for the FDK5N grooved series are in the full catalogue.
Notice that shank length does not scale in a straight line with size. A 4" crimp nipple has almost the same shank as a 3" one. When you swap one maker's fitting for another's, compare K2 against the ferrule or clamp width before you compare price.
5. Clamped or crimped: how the nipple is held in the hose
This is the real choice when you specify a king nipple, and everything else follows from it.
| Clamped | Crimped | |
|---|---|---|
| Typical series | FDKP plated carbon steel, FDKS SS304 | FDK5N grooved, FDK6N |
| Held by | Band clamp, T-bolt clamp or interlocking clamp | Slotted ferrule (F60) or external swage collar (F70) |
| Size range | 1/2" – 12" | 1-1/2" – 6" |
| Assembled | On site, with hand tools; can be cut back and rebuilt | On a crimping machine, at a hose shop |
| Best for | Water transfer, irrigation, construction dewatering, general suction and discharge | Oil, fuel and chemical transfer, dock and marine loading, wire-braid and spiral hose |
6. How to install a clamped king nipple
- Cut the hose square. An angled cut leaves one side of the shank uncovered and is where leaks start.
- Push the hose fully home over the serrations until it meets the collar. Soapy water helps on stiff hose; do not use oil or grease, which lets the hose walk off later.
- Position the clamp over the serrations, not over the collar and not past the last ridge. On large sizes use two clamps, staggered so the bolts are not in line.
- Tighten evenly to the clamp maker's figure. Over-tightening a band clamp cuts the hose cover and reduces grip.
- Seal the thread with PTFE tape or pipe paste and make it up into the port; tapered threads seal by wedging, so do not force past firm hand-tight plus the usual turns.
- Re-check the clamp after the first run. Rubber relaxes in the first hours of service; a quarter turn then saves a blown hose later.
A crimped assembly is different: the ferrule is chosen to the hose OD and crimped to a set diameter on a machine. That is a hose-shop job, and the right ferrule for each hose is covered in our ferrule selection guide.
7. Pressure: rate the assembly, not the fitting
Our FDKP and FDKS king nipples are rated to 200 psi maximum working pressure for the fitting on its own. That is not the number to design to. A finished hose assembly is limited by whichever of these gives first:
- The hose. Its own working pressure almost always governs, and no fitting raises it.
- The retention method. A clamp on a serrated shank releases before a crimped ferrule does. That is why higher-pressure service moves to a crimped nipple; our F70 external swage ferrule with collar is rated to 300 psi working pressure.
- The fitting. Material and wall only become the limit at the top of the range.
8. Where a king nipple should not be used
Steam: never, in any size or material. Steam hose needs ground-joint fittings with matching safety clamps.
Heavy-duty compressed air and other stored-energy gas: not on a clamped king nipple, and particularly not at 1-1/4" and above, where the shank can blow off under load. A liquid line that fails drops its pressure at once; a gas line releases the fitting with the stored energy behind it. Gas duty belongs on a crimped termination.
9. King nipple vs hose barb vs ground joint
| King nipple | Small hose barb | Ground joint (steam) | |
|---|---|---|---|
| Typical size | 1/2" – 12" | 1/8" – 1" | 1/2" – 2" |
| Shank | Long, deep serrations, sized for a clamp or ferrule | Short barbs, often push-on | Spud with a ground seat, held by a two-part clamp |
| Material | Plated steel, stainless | Usually brass or plastic | Plated iron or steel |
| Job | Industrial suction and discharge hose | Tubing, low-pressure air and fluid | Steam and hot water hose |
10. Materials
Plated carbon steel covers water, air and general industrial duty and is the most economical choice. SS304 stainless is for media or washdown regimes that would strip a plated surface, such as food plants, fertiliser and mild chemicals. For acids and aggressive chemicals, check compatibility with the hose maker first; the hose usually limits the chemical rating before the fitting does.
Frequently asked questions
Is a king nipple the same as a KC nipple?
Yes. King nipple, KC nipple, king combination nipple and combination nipple are the same fitting.
What thread does a king nipple have?
NPT in North America, BSPT in Australia, the UK, Europe and the Middle East. They are not interchangeable.
How do I measure which size I need?
Measure the hose inside diameter; that is the king nipple size. Then confirm the thread on the equipment it will screw into, by size and by threads per inch.
How many clamps should I use?
One is usual on small sizes. From about 2" and on any hose that sees surge or vacuum, two clamps with the bolts staggered is standard practice, provided the shank is long enough to take both on the serrations.
What pressure is a king nipple rated for?
Our FDKP and FDKS series are rated to 200 psi for the fitting alone. The working pressure of the assembly is set by the hose and the retention method.
Need king nipples for a distribution program?
Sunze has made king nipples, ferrules and hose clamps in Taiwan since 1976. ISO 9001, NPT or BSP, plated steel or SS304, 1/2" to 12", private label welcome. Send us the sizes and thread standard and we will quote within 24 hours.
Request a quotation