{"id":5271,"date":"2026-09-19T03:31:44","date_gmt":"2026-09-19T03:31:44","guid":{"rendered":"https:\/\/www.henghuahose.com\/?post_type=product&p=5271"},"modified":"2026-09-19T03:31:45","modified_gmt":"2026-09-19T03:31:45","slug":"metric-male-l-series-hollow-hex-plug-iso-6149-3-4hn","status":"publish","type":"product","link":"https:\/\/www.henghuahose.com\/pt\/product\/metric-male-l-series-hollow-hex-plug-iso-6149-3-4hn\/","title":{"rendered":"4HN Hollow Hex Plug – Metric Male L-Series ISO 6149-3 Port Blanking Plug"},"content":{"rendered":"
The 4HN hollow hex plug is a metric male blanking plug that closes an ISO 6149-1 port using the light duty L series stud end geometry of ISO 6149-3. An O-ring sits in a machined groove behind the straight metric thread, and the plug is driven from a small internal hex machined into the closed end. Because the drive is internal, the body stays short, so the plug blanks a port with a low profile instead of standing proud above the manifold face.<\/p>\r\n\r\n\r\n\r\n
Principais vantagens<\/h2>\r\n\r\n\r\n\r\n
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Correct L series stud end geometry for ISO 6149-1 ports, so the plug threads straight into the port without a reducer or an adaptor.<\/li>\r\n\r\n\r\n\r\n
Internal hex drive inside the closed end gives a short body for low profile blanking.<\/li>\r\n\r\n\r\n\r\n
O-ring sealing in the port recess, with the straight metric thread used only to clamp the plug down.<\/li>\r\n\r\n\r\n\r\n
Ten printed sizes from M10X1 to M48X2 covering the common metric light duty port range.<\/li>\r\n\r\n\r\n\r\n
Carbon steel with trivalent chromium zinc plating, or 304 \/ 316 stainless steel for corrosive duty.<\/li>\r\n\r\n\r\n\r\n
NBR, FKM and EPDM seal options to match fluid and temperature.<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n
1. What a 4HN Hollow Hex Plug Does<\/h2>\r\n\r\n\r\n\r\n
A 4HN hollow hex plug is a single-ended part that terminates a hydraulic port. The male stud end is threaded to ISO 6149-3, the metric stud end standard for light duty O-ring sealing, and it is made to enter a port machined to ISO 6149-1. Once seated, the body continues the wall of the housing and stops the flow path: this port plug has no second connection, no bore through the part and no outlet.<\/p>\r\n\r\n\r\n\r\n
The core value of the part is the accuracy of that stud end match. A blanking plug works only when the thread form, the groove position and the O-ring cross section all line up with the port that receives them, because a straight thread O-ring joint seals on the elastomer compressed in the recess, not on the thread itself. If any one of those three features is wrong, no amount of torque will stop the joint from weeping.<\/p>\r\n\r\n\r\n\r\n
Metric O-ring stud ends follow one sealing principle across the whole family. The O-ring is compressed in the machined recess on the port face, the straight thread holds the plug down against that recess, and the shoulder contact fixes the squeeze on the O-ring. This is why a thread sealant is never a substitute for the O-ring on this family. The same principle governs the BSP family under ISO 1179 and the SAE family under ISO 11926, with different thread forms and recess dimensions in each case.<\/p>\r\n\r\n\r\n\r\n
The 4HN version adds an internal hex drive. A hex key enters the closed end of the plug and turns the part from inside the body. The outside of the body is then free of hex flats, which allows a shorter overall length and a tighter envelope. A maintenance engineer working on a stacked manifold often cannot swing a spanner or a socket around an external hex plug, but an internal hex key only needs axial access. That is the practical reason this hydraulic plug version exists alongside the external hex plug in the same metric adapter range.<\/p>\r\n\r\n\r\n\r\n
2. 4HN Specifications<\/h2>\r\n\r\n\r\n\r\n
2.1 Connection 1 – Metric male stud end, ISO 6149-3 L series<\/h3>\r\n\r\n\r\n\r\n
Connection 1 is a metric male stud end made to ISO 6149-3, the light duty L series of metric stud ends with O-ring sealing. Thread sizes run from M10X1 to M48X2 in the printed range, covering the metric light duty port steps. The thread is straight, not tapered, and the sealing element is an O-ring carried in a groove machined behind the thread on the stud end.<\/p>\r\n\r\n\r\n\r\n
The mating port is an ISO 6149-1 metric port: a straight metric thread with a machined recess on the port face that accepts the O-ring. The printed catalogue note for this series states that the plug fits an ISO 9974-1 port, or an ISO 6149-1 port when a retaining ring is not used. Buyers who are blanking an ISO 6149-1 port should confirm the recess dimensions of their port against the stud end drawing before ordering.<\/p>\r\n\r\n\r\n\r\n
The L series designation matters. ISO 6149-3 is the light duty metric stud end, and it is dimensionally different from the heavy duty S series under ISO 6149-2. The two look similar at a glance, but the stud length and the groove position differ, which is why a metric adapter part from one series cannot be substituted for the other in the same port.<\/p>\r\n\r\n\r\n\r\n
2.2 Connection 2 – Closed end with internal hex drive<\/h3>\r\n\r\n\r\n\r\n
Connection 2 is a closed end, not a second port. The body terminates after the hex and there is no through bore, no second thread and no outlet, so the part cannot join two lines. Its only function on this end is to provide the drive feature that turns the plug into the port.<\/p>\r\n\r\n\r\n\r\n
The drive is an internal hex recess machined into the closed end. The printed body hex dimension S1 does not describe flats on the outside of the body on this series. Instead it records the width across flats of the internal hex that the key engages. In the printed range the internal hex runs from 5 mm at the M10X1 size to 24 mm at the M48X2 size, so the wall of the body stays proportionate to the port it closes.<\/p>\r\n\r\n\r\n\r\n
Because the drive is inside the body, a hollow hex plug can be shorter than an external hex plug for the same port size. It also removes any sharp hex corners from the outside of the assembly, which matters where a hose, a tube run or a neighbouring component passes close to the blanked port.<\/p>\r\n\r\n\r\n\r\n
2.3 Construction and Materials<\/h3>\r\n\r\n\r\n\r\n
The body is machined from bar stock on CNC lathes. The stud end is turned to the L series profile with the O-ring groove cut to the standard position, the internal hex is formed in the closed end, and the thread is produced to the printed metric designation. Every batch is checked against the drawing with thread gauges before packing.<\/p>\r\n\r\n\r\n\r\n
Body material options are carbon steel, 304 stainless steel, 316 stainless steel and brass, with the standard carbon steel body supplied with trivalent chromium zinc plating as the general hydraulic finish. Zinc-nickel plating is available where a higher corrosion class is required. Stainless steel bodies are normally supplied unplated for offshore, marine and process service.<\/p>\r\n\r\n\r\n\r\n
The seal on this series is an O-ring, and the printed O-ring column lists the size for each row as an inside diameter and a cord diameter, for example O08.1X1.6 at the M10X1 size. Seal material options are NBR for mineral hydraulic oil, FKM for higher temperature and aggressive fluids, and EPDM for water, steam and many brake fluid applications. The O-ring material must be compatible with the fluid in the system, because the seal is the only pressure barrier on the joint.<\/p>\r\n\r\n\r\n\r\n
2.4 Pressure and Temperature<\/h3>\r\n\r\n\r\n\r\n
The printed dimension chart for this series has no pressure column, and no per-size pressure rating is stated on this page. Working pressure for these sizes is confirmed per order by HENGHUA engineering, based on the thread size, sealing method and material selected. This keeps the figure tied to the actual body material, plating and seal compound of the order rather than to a blanket table value.<\/p>\r\n\r\n\r\n\r\n
Temperature capability follows the seal material, which is a material fact rather than a rating of the fitting. NBR covers approximately -30\u00b0C to +100\u00b0C, FKM covers approximately -20\u00b0C to +200\u00b0C, and EPDM covers approximately -40\u00b0C to +120\u00b0C. The carbon steel body with zinc plating is suitable for general hydraulic service, and 304 or 316 stainless steel is used where the environment is corrosive.<\/p>\r\n\r\n\r\n\r\n
Two practical limits sit outside the seal itself. The first is the pressure class of the port the plug is closing, because a light duty L series port is intended for the light duty working range. The second is the internal hex, which should be turned with a key that fills the recess properly so the drive does not strip under a high tightening load.<\/p>\r\n\r\n\r\n\r\n
2.5 Part Number and Dimension Table<\/h3>\r\n\r\n\r\n\r\n
The table below is reproduced from the printed dimension chart for this series.<\/p>\r\n\r\n\r\n\r\n
Printed note on the chart: “Fit for ISO 9974-1 port or ISO 6149-1 port when useless of retaining ring.”<\/p>\r\n\r\n\r\n\r\n
What each column means:<\/p>\r\n\r\n\r\n\r\n
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PART NO. – the full series part number to quote on a purchase order, built from the 4HN prefix and the dash size code.<\/li>\r\n\r\n\r\n\r\n
E – connection 1, the metric male stud end thread of the L series, printed as the nominal diameter and pitch, for example M22X1.5.<\/li>\r\n\r\n\r\n\r\n
O-RING E – the O-ring that belongs on the E end of that row, printed as inside diameter x cord diameter, for example O19.3X2.4.<\/li>\r\n\r\n\r\n\r\n
A – the stud length from the end face of the plug to the hex or shoulder face, in millimetres.<\/li>\r\n\r\n\r\n\r\n
L – the overall length of the plug from end to end, in millimetres.<\/li>\r\n\r\n\r\n\r\n
S1 – the width across flats of the internal hex drive, in millimetres.<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n
Thread size and dash chart, showing the size steps in the printed range:<\/p>\r\n\r\n\r\n\r\n
3. How to Read a 4HN Hollow Hex Plug Part Number<\/h2>\r\n\r\n\r\n\r\n
The 4HN hollow hex plug part number carries two elements. The prefix 4HN identifies the series: a blanking plug in the metric L series with O-ring sealing and an internal hex drive. The suffix after the dash is the size code, and it corresponds to the metric thread of the stud end.<\/p>\r\n\r\n\r\n\r\n
Take the printed row 4HN-22. The prefix 4HN places the part in the metric L series hollow hex plug range. The size code 22 gives a stud end thread of M22X1.5, an O-ring of O19.3X2.4 on that end, a stud length A of 13.0 mm, an overall length L of 16 mm and a 10 mm internal hex drive. A buyer searching for a hydraulic plug for a size 22 light duty metric port can therefore order straight from the chart without converting anything.<\/p>\r\n\r\n\r\n\r\n
The same prefix logic applies in the neighbouring metric adapter and SAE families. The external hex version of the same metric L series plug carries a different prefix, and the SAE O-ring boss hollow hex plug carries its own prefix because it uses an inch thread form and an inch O-ring. Reading the prefix first, then the size code, then checking the thread column is the fastest way to avoid mixing one family into another.<\/p>\r\n\r\n\r\n\r\n
On a purchase order, add the material and the seal compound after the part number, because the base number fixes only the geometry. A zinc plated carbon steel body with an NBR O-ring and a 316 stainless steel body with an FKM O-ring share one part number but are not the same product.<\/p>\r\n\r\n\r\n\r\n
4. Installation and Fitment<\/h2>\r\n\r\n\r\n\r\n
Installation of this series follows the rules of any straight thread O-ring joint. The O-ring is the seal and the thread is only the clamp. Thread sealant, PTFE tape or a gasket washer must never be used as a substitute for the O-ring on this plug, because those materials change the position of the plug in the port and can force the shoulder off its seat.<\/p>\r\n\r\n\r\n\r\n
Assembly steps:<\/p>\r\n\r\n\r\n\r\n
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Confirm the port is an ISO 6149-1 metric O-ring port and check the thread designation against the part number before starting.<\/li>\r\n\r\n\r\n\r\n
Clean the port recess, the thread and the O-ring groove. Remove swarf, old sealant residue and any trace of a previous O-ring.<\/li>\r\n\r\n\r\n\r\n
Fit a new O-ring of the correct size and material into the stud end groove, and check that it sits fully in the groove and is not twisted.<\/li>\r\n\r\n\r\n\r\n
Lubricate the O-ring and the thread lightly with clean system fluid or a compatible assembly lubricant so the elastomer slides instead of rolling.<\/li>\r\n\r\n\r\n\r\n
Start the plug by hand and turn it in until it is finger tight, keeping the body square to the port. Do not let the thread cross.<\/li>\r\n\r\n\r\n\r\n
Tighten with a hex key that fills the internal recess, turning the plug down until the shoulder meets the port face squarely. Torque is applied in words, not as a fixed number: the plug is brought to a firm seat with a steady pull on a key that fits the hex correctly, without forcing the body past the point where the shoulder stops.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
Common errors and their symptoms:<\/p>\r\n\r\n\r\n\r\n
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O-ring left out or rolled out of the groove: the port weeps along the thread, and no further tightening stops it.<\/li>\r\n\r\n\r\n\r\n
Thread sealant or tape used instead of the O-ring: the plug sits too high, the shoulder never meets the recess, and the joint leaks at the same rate as before.<\/li>\r\n\r\n\r\n\r\n
Wrong series plug used in the port: an S series stud end is too long for an L series port, so the shoulder bottoms before the O-ring is compressed.<\/li>\r\n\r\n\r\n\r\n
Cross-threaded start: the plug turns with a rough feel, the thread is damaged and the stud end will not seal.<\/li>\r\n\r\n\r\n\r\n
Over tightening with an undersized key: the internal hex rounds off, and the plug can only be removed by other means.<\/li>\r\n<\/ul>\r\n\r\n\r\n\r\n
Reuse policy for this port plug is simple. The steel body can be reused if the thread, the shoulder face and the O-ring groove are undamaged. The O-ring is a single-use elastomer and is replaced every time the plug is removed.<\/p>\r\n\r\n\r\n\r\n
5. Applications and Industries<\/h2>\r\n\r\n\r\n\r\n
The 4HN hollow hex plug is used wherever a metric port has to be blanked on a machine that is shipped, stored or reconfigured. Application tags for the series are hydraulic systems, water jetting, oil and gas, industrial equipment, construction machinery, agriculture, marine and material handling.<\/p>\r\n\r\n\r\n\r\n
Four concrete scenarios illustrate the range. On a construction machine, a spare metric port on a valve block is blanked with this plug so the machine can be delivered without an auxiliary circuit. In industrial equipment, a manufacturer keeps a family of manifold blocks in stock and blanks the ports that the standard build does not use, then removes the plug when a customer option is added. In oil and gas service, a stainless steel body with an FKM O-ring is used on a skid that sees washdown and a wide temperature swing. In a maintenance workshop, this hydraulic plug is the standard way to close a metric port after a test point or a gauge line is removed, and a spare port plug is kept on the shelf for the next job.<\/p>\r\n\r\n\r\n\r\n
Because the drive is internal, the part also suits machines where the blanked port sits close to another component. There is no external hex to catch on a hose or a harness, and a hex key can reach the drive from directly above the port.<\/p>\r\n\r\n\r\n\r\n
6. Replacement and Cross-Reference Guide<\/h2>\r\n\r\n\r\n\r\n
Cross-reference for this family is organised by standard and sealing method, never by brand. A 4HN hollow hex plug is identified by three things: the thread, the seal type and the seat geometry. Measure all three before ordering a replacement.<\/p>\r\n\r\n\r\n\r\n
Measure these three things:<\/p>\r\n\r\n\r\n\r\n
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The thread. Measure the outside diameter and the pitch of the male stud end with a thread gauge or a caliper. A print of M22X1.5 means a nominal 22 mm diameter with a 1.5 mm pitch, which is a metric L series size.<\/li>\r\n\r\n\r\n\r\n
The seal. Confirm that the port has a machined recess on its face and that the old part carries an O-ring in a groove. If the port is a plain flat face, the joint is a different sealing method and this series is not the correct replacement.<\/li>\r\n\r\n\r\n\r\n
The seat or drive. On this series the drive is internal, so confirm the width across flats of the recess in the closed end matches the key available, and confirm that the stud length in the chart matches the port depth.<\/li>\r\n<\/ol>\r\n\r\n\r\n\r\n
The most common cross-reference error in the metric O-ring family is mixing the L series with the S series. ISO 6149-3 is the light duty stud end and ISO 6149-2 is the heavy duty stud end. They use the same sealing principle but different stud lengths and groove positions, so the two are not interchangeable in the same port even when the thread designation looks similar.<\/p>\r\n\r\n\r\n\r\n
A second error is mixing a metric O-ring plug with a BSP or an SAE O-ring boss plug. The thread angle, the pitch and the groove position are all different between ISO 6149 metric ports, ISO 1179 G ports and ISO 11926 SAE ports. Threading a metric plug into a G port will feel close but will not seal, and it damages the port.<\/p>\r\n\r\n\r\n\r\n
7. Ordering, Packaging and Delivery<\/h2>\r\n\r\n\r\n\r\n
To order a 4HN hollow hex plug, quote the series code, the full part number, the thread size, the seal material, the body material and plating, and the quantity. A complete line reads as follows: series 4HN, part number 4HN-22, thread M22X1.5, NBR O-ring, carbon steel with trivalent chromium zinc plating, quantity required. Where a drawing exists for an OEM programme, attach it so the internal hex and the stud dimensions are confirmed against the print.<\/p>\r\n\r\n\r\n\r\n
Packaging is arranged in two ways. Distributor orders are packed in labelled cartons with the part number and the size on the outside, so the box can go straight onto a shelf or into a bin location. Direct-to-line OEM orders are packed in the sequence the customer consumes them, so the parts can be issued to assembly without re-sorting.<\/p>\r\n\r\n\r\n\r\n
Samples are available for validation before a production order, including the material and seal combination that the final order will use, and the hydraulic adapter supplier keeps the same seal compound for the production run. Lead time is confirmed per order by the hydraulic adapter supplier, because the material, the plating and the seal compound all affect the schedule. HENGHUA confirms the delivery date in writing with the order acknowledgement.<\/p>\r\n\r\n\r\n\r\n
8. FAQ<\/h2>\r\n\r\n\r\n\r\n
What is the difference between a straight-thread O-ring seal and a tapered pipe thread?<\/strong><\/p>\r\n\r\n\r\n\r\n
A straight-thread O-ring joint, such as the ISO 6149-1 port closed by a 4HN hollow hex plug, seals on an elastomeric O-ring compressed in a machined recess on the port face. The thread is straight and does the clamping only, so the joint does not depend on thread deformation. A tapered pipe thread seals by wedging the two thread flanks together with a sealant, which is a different principle and a different port preparation.<\/p>\r\n\r\n\r\n\r\n
Can BSP and NPT be interchanged?<\/strong><\/p>\r\n\r\n\r\n\r\n
No. A G (BSPP) thread to ISO 228-1 and an NPT thread have different thread forms, different flank angles and different pitches, so they will not seal against each other even when the nominal size looks close. The same rule applies across the O-ring families: an ISO 1179 G port, an ISO 6149 metric port and an ISO 11926 SAE port each need their own stud end. Use the thread designation on the drawing, not the nominal size, to decide.<\/p>\r\n\r\n\r\n\r\n
How do I identify the correct 4HN size?<\/strong><\/p>\r\n\r\n\r\n\r\n
Measure the outside diameter and the pitch of the port thread, then match the pair to the E column of the printed chart, which steps from M10X1 to M48X2. Confirm the port has a recessed O-ring seat, since that is what identifies the ISO 6149-1 port family. Then read across the row for the O-ring size, the stud length A, the overall length L and the internal hex S1.<\/p>\r\n\r\n\r\n\r\n
What seal material should I select for my fluid and temperature?<\/strong><\/p>\r\n\r\n\r\n\r\n
NBR is the default for mineral hydraulic oil over approximately -30\u00b0C to +100\u00b0C. FKM suits higher temperature service up to approximately +200\u00b0C and many aggressive fluids, with a low end of approximately -20\u00b0C. EPDM covers approximately -40\u00b0C to +120\u00b0C and is the choice for water, steam and many brake fluid duties, but it is not compatible with mineral oil. The O-ring seals the joint, so the compound has to match the fluid.<\/p>\r\n\r\n\r\n\r\n
How is the working pressure of this fitting determined?<\/strong><\/p>\r\n\r\n\r\n\r\n
The printed chart for this series carries no pressure column, and no per-size rating is printed on the page. Working pressure for these sizes is confirmed per order by HENGHUA engineering, based on the thread size, sealing method and material selected. The service pressure must also stay inside the pressure class of the light duty port being blanked.<\/p>\r\n\r\n\r\n\r\n
What is the minimum order quantity and can I get samples?<\/strong><\/p>\r\n\r\n\r\n\r\n
Minimum order quantity is set per part number and per material combination, so it is confirmed with the quotation rather than fixed in advance. Samples are available for validation, and they are produced with the same material and seal compound as the intended production order so the test result carries over. Send the part number, the material and the seal choice when requesting samples.<\/p>\r\n\r\n\r\n\r\n
What is the difference between a 4HN hollow hex plug and an external hex plug of the same series?<\/strong><\/p>\r\n\r\n\r\n\r\n
The two share the L series stud end, the O-ring groove and the thread sizes, so both seal on the same ISO 6149-1 port. The difference is the drive. The 4HN version is turned from an internal hex recess in the closed end, which keeps the body short and leaves no hex corners on the outside. The external hex version uses flats on the body and is tightened with a spanner or a socket, which is easier where there is room around the port.<\/p>\r\n\r\n\r\n\r\n
Can this plug be used in a port that has a retaining ring?<\/strong><\/p>\r\n\r\n\r\n\r\n
The printed note on the chart states that the plug fits an ISO 9974-1 port, or an ISO 6149-1 port when a retaining ring is not used. Where the port is fitted with a retaining ring, the recess geometry differs and the fit should be confirmed before ordering. Send the port drawing with the inquiry so the stud length and the groove position can be checked against it.<\/p>\r\n\r\n\r\n\r\n
HENGHUA is a hydraulic adapter supplier and manufacturer producing the 4HN hollow hex plug range in metric L series ISO 6149-3 geometry, from M10X1 to M48X2, with carbon steel, stainless steel and brass body options and NBR, FKM or EPDM seals. Send the port size, the material, the seal compound and the quantity you need, and we will quote the part number and the lead time for your programme.<\/p>\r\n\r\n\r\n\r\n
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