5N NPT Male to NPT Female Adapter – 5N Adapter for Taper Pipe Thread Extension and Size Change

The 5N adapter is a hydraulic conversion adapter with an NPT male end on one side and an NPT female tapped port on the other. It extends a taper pipe thread run, changes from one NPT size to another, or provides a female port where only a male nipple was available. Both connections are taper pipe threads, so both seal on the thread flanks and both require a suitable thread sealant.

Core Advantages

• Male and female NPT ends on one machined body, for extension, size change or gender change in a pipe thread circuit.
• Thirty-five catalogue rows covering NPT sizes from Z1/8″x27 up to Z2″x11.5, including reducing combinations.
• Straight body with a single hex, so the adapter can be held while each end is tightened.
• Machined from bar stock on CNC lathes, with thread gauges applied batch by batch before packing.
• Carbon steel with trivalent chromium zinc plating, or 304 / 316 stainless steel for corrosive and marine duty.
• Female end is a tapped port machined directly into the body, so no separate female fitting is needed.

1. What a 5N Adapter Does

A 5N adapter joins an NPT male taper pipe thread to an NPT female tapped port. It is a hydraulic conversion adapter in the taper pipe thread family and a thread adapter in the literal sense, because the two ends carry different thread forms of one standard. The male end presents an external taper thread with its own thread length, and the female end is a taper pipe port machined into the opposite side of the same body. Fluid passes straight through, so the part extends a run, reduces from one NPT size to another, or converts a male thread into a female port.

Both ends must match their mating part exactly, because that is the precondition for eliminating leakage at the conversion point. A taper pipe joint does not seal on a seat, a flare or an O-ring: it seals on the interfering thread flanks, which is why the thread form, the pitch and the size have to be correct on both sides of the adapter.

The sealing principle of this hydraulic conversion adapter is thread-flank sealing, and it is the same at both ends. As the male taper thread is screwed into the female taper thread, the flanks interfere progressively along the taper, and the joint becomes pressure-tight only when a sealant suited to the fluid is present on the threads. The female end is a tapped port, an internally threaded hole in the body, not a swivel nut.

Taper pipe threads must never be interchanged with other pipe thread standards. NPT and BSPT look similar and are both taper threads, but they follow different standards and different thread forms, so an NPT male end will not seal correctly in a BSPT female port, and a BSPT male end will not seal correctly in an NPT female port.

2. 5N Specifications

2.1 Connection 1 – NPT male taper pipe thread

• Thread standard and family: taper pipe thread per ANSI/ASME B1.20.1 (NPT), with the dryseal NPTF form covered by SAE J476. The catalogue uses the Z prefix for taper pipe thread, so Z1/2"X14 means a 1/2″ NPT thread with 14 threads per inch.
• Thread size range: Z1/8″x27, Z1/4″x18, Z3/8″x18, Z1/2″x14, Z3/4″x14, Z1″x11.5, Z1.1/4″x11.5, Z1.1/2″x11.5 and Z2″x11.5, across the catalogue rows.
• Gender: male, external taper thread with its thread length marked A on the drawing.
• Sealing method: the NPT male end seals on the thread flanks. Seat the thread with a sealant compatible with the fluid; there is no O-ring, no cone seat and no flange face in this joint.
• Mating port standard: an NPT or NPTF female taper pipe port of the same nominal size. NPT and BSPT must never be interchanged: BSPT is defined by ISO 7-1, has a different thread form and a different pitch, and cannot be substituted for NPT on either side of the joint. The male end of this NPT adapter is therefore matched to a port of the same standard and size.

2.2 Connection 2 – NPT female tapped port

• Thread standard and family: taper pipe thread per ANSI/ASME B1.20.1, with the dryseal NPTF form covered by SAE J476.
• Thread size range: the same family as the male end, from Z1/8″x27 to Z2″x11.5, so the series covers same-size adapters and reducing adapters.
• Gender: female. This end is a tapped port, an internally threaded taper hole machined into the body.
• Sealing method: thread-flank sealing, identical in principle to the male end. The mating male nipple is screwed in and the joint is made tight with a sealant suited to the fluid.
• Mating port standard: an NPT or NPTF male taper pipe thread of the same nominal size.

2.3 Construction and Materials

The body is machined from bar stock as one piece on CNC lathes, with the male thread, the tapped port and the hex produced in a single part so the threads stay in line and the bore is continuous. Both threads are cut to the taper pipe thread form of their size, and both are gauged before packing.

Carbon steel is the standard body material, with trivalent chromium zinc plating (Cr3+) for general hydraulic service and zinc-nickel plating available where a harder deposit is preferred. For corrosive and offshore duty, 304 stainless steel and 316 stainless steel are the alternative body grades, and brass is available for selected sizes and compatible duties.

This series carries no elastomeric seal of its own, because both connections seal on the thread flanks. Hex width S1 is machined on the body between the two ends, and there is no lock nut, bulkhead feature or swivel, so this thread adapter is a rigid one-piece part.

2.4 Pressure and Temperature

The printed table for this series carries no pressure column, so no per-size working pressure is quoted here. Working pressure for these sizes is confirmed per order by HENGHUA engineering, based on the thread size, the sealing method and the material selected. Size, body wall thickness, thread form and body material all govern the result, and the taper pipe thread joint is usually the practical limit on the line.

Temperature range follows the body material and the sealant, because there is no soft seal in the body. As material facts: carbon steel with zinc plating suits general hydraulic service, 304 and 316 stainless steel are selected for corrosive environments, and brass is available for compatible duties. The thread sealant must be selected for the fluid and the operating temperature, and where the wider circuit carries an O-ring, that compound sets its own envelope: NBR approximately -30°C to +100°C, FKM approximately -20°C to +200°C, and EPDM approximately -40°C to +120°C.

2.5 Part Number and Dimension Table

What each column means:

• PART NO. – the HENGHUA catalogue number. 5N is the series code, followed by the size code of the male end and, where the ends differ, the size code of the female end.
• E – the external (male) taper pipe thread, written with the Z prefix, for example Z3/8″X18.
• F – the internal (female) taper pipe thread of the tapped port, also written with the Z prefix.
• A – the threaded length of the male end, in mm, measured on the printed drawing from the thread end back towards the hex.
• L – the overall length of the adapter from end to end, in mm.
• S1 – the across-flats width of the hex on the body, in mm, for holding with a wrench.

Thread size and dash chart, read from the same table:

The size steps follow the taper pipe thread series, so order by the NPT size at each end rather than by an equivalent hose or tube dash number.

3. How to Read a 5N Part Number

5N is the series code of this NPT adapter. In the HENGHUA American Adapters numbering the leading digit places the part in the male-to-female adapter family and the letter N identifies the NPT taper pipe thread interface, so the code itself tells the buyer that both ends of this thread adapter are taper pipe threads.

The first size group after the series code is the male end and the second group, when present, is the female end. The codes follow the NPT sizes in the table: 02 for 1/8″, 04 for 1/4″, 06 for 3/8″, 08 for 1/2″, 12 for 3/4″, 16 for 1″, 20 for 1.1/4″, 24 for 1.1/2″ and 32 for 2″.

When only one size group appears, both ends are that size. 5N-08 is therefore a 1/2″ NPT male to 1/2″ NPT female adapter, with male thread Z1/2″x14, female thread Z1/2″x14, thread length A of 19.5 mm, overall length L of 47.5 mm and hex S1 of 30 mm.

Worked example, 5N-08-04: two groups, so the male end is 1/2″ and the female end is 1/4″. The row returns male thread Z1/2″x14, female thread Z1/4″x18, thread length A of 19.5 mm, overall length L of 28 mm and hex S1 of 24 mm. This is the reducing adapter used when a 1/2″ pipe thread has to feed a 1/4″ pipe port.

4. Installation and Fitment

Both ends tighten on the same principle, and both depend on the threads being clean and correctly sealed. Apply a sealant suited to the fluid to the male thread, screw the male end into its port by hand first, then tighten. On the female end, apply sealant to the male nipple that enters the tapped port, screw it in by hand, then tighten. No tightening angle is published in this catalogue for the series, so the torque practice follows the mating components and the machine specification.

Because the joint seals on the thread flanks, thread preparation is part of installation rather than a detail. Clean both threads, remove old sealant and metal debris, apply fresh sealant to the male thread only, and leave the first thread or two clean so excess sealant is not pushed into the fluid path.

Keep the tapped port capped until assembly, start every thread by hand before using a wrench, and hold the adapter on hex S1 rather than on the body or the opposite thread, so neither joint is turned on the wrong thread.

Assembly steps:

1. Confirm the two thread sizes from the part number and the table row, male end first and female end second.
2. Inspect both threads for damage and clean out old sealant and debris.
3. Apply a fluid-compatible sealant to the male thread that will enter the port.
4. Hold the adapter on hex S1, start the male end by hand and tighten it into its port.
5. Apply sealant to the mating nipple, start it by hand into the tapped port and tighten it, again holding the adapter on S1.
6. Pressurise the line and check both joints for weepage before the machine returns to service.

Common fitment errors and their symptoms:

• A BSPT male nipple threaded into the NPT female end. The threads engage on the wrong form, the joint does not seat correctly and it leaks under pressure. NPT and BSPT must never be interchanged.
• No sealant on the male end. The line weeps along the thread flanks, because this connection has no elastomer and no seat.
• Excessive sealant. Sealant enters the fluid path, or the thread cannot run in far enough and the adapter stands proud of the port.
• Tightening on the body instead of the hex. The adapter distorts, or the opposite thread is loosened or over-tightened.
• Mismatched size code. The male thread starts in the port but runs out of engagement before it seats, which usually means the port is one size smaller.
• Reusing a thread that has already been deformed. A galled or cross-threaded taper will not seal on a second assembly, and the adapter should be replaced.

Reuse policy: the body of a 5N adapter may be cleaned and reused if both threads are undamaged and still engage cleanly. Old sealant is removed and new sealant applied at every re-assembly, and a thread that has been cross-threaded or galled is not reused.

5. Applications and Industries

Application tags for the 5N series: hydraulic systems, water jetting, oil and gas, industrial equipment, construction machinery, agriculture, marine and material handling.

Concrete scenarios where this adapter is specified:

• Extension and take-off points. The 5N adapter extends a taper pipe thread outward from a port so a gauge, hose end or valve can be fitted where the port face alone would not give enough thread engagement.
• Size change in a pipe thread circuit. With 35 rows covering reducing combinations, the series lets a large port feed a small line, or the reverse, without cutting and re-threading pipe.
• Gender change on repair jobs. Where a male nipple is in place but the new component needs a female port, the adapter supplies the female end on the same taper thread standard.
• Test and flushing benches, and OEM kits. A compact adapter that reads one size at each end keeps a manifold build simple, and distributors hold the series so a machine can be configured to the customer’s pipe thread at assembly.

6. Replacement and Cross-Reference Guide

Cross-reference for this series is organised by standard, thread size and sealing method, never by brand. Three questions decide the correct replacement: which taper pipe thread standard the part follows, which size each end carries, and how the joint is sealed.

Measure these three things before ordering a replacement 5N adapter:

1. The thread standard. NPT follows ANSI/ASME B1.20.1 with a 60° thread angle, and the dryseal NPTF form follows SAE J476, while BSPT follows ISO 7-1 with a 55° thread form. Check the thread angle and the pitch, because the two families look similar but are not interchangeable.
2. The thread size at each end. Measure the outside diameter over the male thread and count the threads per inch, and match the result against the E column. Identify the female end by its pitch and taper and match it against the F column.
3. The sealing method. Confirm that both ends are taper pipe threads sealed on the flanks with a sealant. A part that seals with an O-ring, a cone or a flat face is a different series, even where the thread looks similar.

A practical check on this NPT adapter is to screw the mating nipple into the female end by hand and count the turns. Where a size or finish outside the standard list is needed, a hydraulic adapter supplier with its own machining capacity can quote it against the drawing.

7. Ordering, Packaging and Delivery

To order a 5N adapter, give the series code, the full part number, both thread sizes, the body material, the plating and the quantity, and state the fluid so the sealant recommendation can be confirmed. A complete line reads, for example: 5N-16-08, male end Z1″x11.5, female end Z1/2″x14, carbon steel with trivalent chromium zinc plating, quantity 200 pieces.

If a combination outside the printed table is required, send both thread sizes and the intended fluid, and HENGHUA will confirm whether it can be machined and whether the material and plating are available. Samples are available so the thread fit can be proven against the customer’s own ports, and as a hydraulic adapter supplier HENGHUA quotes the sample line and the production line together.

Packaging follows the usual formats for this range, with bulk cartons and part number labels for distributor stock and labelled bags or boxed kits for direct-to-line delivery. Each carton records the part number, the two thread sizes, the quantity and the batch reference, and lead time is confirmed per order.

8. FAQ

What is the difference between JIC 37° flare and ORFS, and which should I use?

A JIC 37° flare per SAE J514 seals metal to metal on a conical flare face, with a nut drawing the flare into the cone. An ORFS joint per SAE J1453 seals on a flat face against an elastomeric O-ring set in a groove. Select the end that matches the port. This series uses neither: both of its ends are taper pipe threads and both seal on the thread flanks.

Can NPT and BSPT be interchanged?

No. NPT is defined by ANSI/ASME B1.20.1 with a 60° thread angle, and BSPT is defined by ISO 7-1 with a 55° thread form and a different pitch. The two are similar in appearance and must never be interchanged. An NPT part belongs in an NPT port, a BSPT part belongs in a BSPT port, and a series built to one standard cannot be substituted for the other.

How do I identify the correct 5N size?

Identify the male end first by measuring the thread outside diameter and counting the threads per inch, then match it to the E column. Identify the female end by its pitch and taper and match it to the F column. Where the two ends differ, order the row with two size groups, for example 5N-08-04 for a 1/2″ male end and a 1/4″ female end.

What seal material should I select for my fluid and temperature?

This series has no elastomeric seal in its body, so the selection is the thread sealant for both ends. Choose a sealant compatible with the fluid and the operating temperature, and confirm it against the actual fluid rather than the fluid family name. Where the wider circuit uses O-rings, the compound sets its own envelope: NBR approximately -30°C to +100°C, FKM approximately -20°C to +200°C, and EPDM approximately -40°C to +120°C.

How is the working pressure of this adapter determined?

The printed table for this series has no pressure column, so no per-size figure is published. Working pressure for these sizes is confirmed per order by HENGHUA engineering, based on the thread size, the sealing method and the material selected. In service the taper pipe thread joint is generally the limiting element, so it is assessed together with the mating port rather than on its own.

What is the minimum order quantity and can I get samples?

Minimum order quantity is confirmed per order, because it depends on the thread combination, the material and whether the row is a catalogue size or a special. Samples are available for validation so the thread fit can be checked on the customer’s own ports. Send both thread sizes, the body material and the fluid, and HENGHUA will quote the sample line and the production line together.

Does the NPT male end of this adapter need thread sealant?

Yes. A taper pipe thread seals on the thread flanks, not on a seat or an elastomer, so a sealant suited to the fluid is required on the male thread. Without sealant the joint will weep along the threads. Apply the sealant to the male thread only, leave the first thread clean, and do not apply sealant to the tapped port itself.

What is the difference between a 5N adapter and the 1N or 7N series?

The 1N series is an NPT male single-end adapter and the 7N series is an NPT female adapter, so those are used where only one end has to change. The 5N series carries a male end and a female tapped port on one body, for a run that has to be extended, reduced in size or changed in gender in a single step.

HENGHUA is a hydraulic adapter supplier that manufactures the 5N adapter in 35 catalogue rows from Z1/8″x27 up to Z2″x11.5, with both ends on the NPT taper pipe thread standard. Send the two thread sizes, the body material and the circuit fluid, and HENGHUA will confirm the part number, the finish and the delivery schedule for your inquiry.

Related series in the same family: the 1N adapter (straight) and the 7N adapter (straight). Browse the full Hydraulic Adapters range for the complete SAE J514 JIC, NPT, ORFS and ISO 6162 flange families.