8J Adapter – JIC Lock Nut for 74° Cone Studs and Bulkhead Bodies (SAE J514)

The 8J adapter is a JIC lock nut, not a through-flow adapter: a hex nut with one internal thread that runs onto the external thread of a JIC 74° cone stud or bulkhead body and clamps it. It has no bore, no cone and no O-ring, because its job is mechanical rather than hydraulic: it holds a part that seals. The nut is made in the SAE J514 JIC sizes from 7/16″x20 to 2.1/2″x12, and it is the part that locks a bulkhead body to the panel it passes through.

In a hydraulic tube fitting assembly, both faces of this part must match their counterpart exactly, because that is the precondition for eliminating movement, and therefore leakage, at the joint. The internal thread has to match the stem it locks, and the bearing face and hex have to clear the panel or boss they bear against.

Sealing principle of this series: the 8J adapter does not seal anything itself. The joint it serves seals metal-to-metal on the 74° cone of the mating stud, or on the O-ring of an SAE O-ring boss stud end. The lock nut holds the mating body square and stops it rotating.

Core Advantages

• One internal JIC thread per size, from 7/16″x20 to 2.1/2″x12, so the nut can be matched to any JIC 74° cone stud or bulkhead body in the printed range.
• Printed nut height (A) and hex across flats (S1) for every size, so panel clearance and wrench size can be checked before ordering.
• Hex from 17 mm to 70 mm across flats, following the SAE J514 step for each thread size.
• The same dash size that locks a 6J JIC 74° cone bulkhead body also fits the bulkhead stem of the AJ6JJ bulkhead branch tee.
• Carbon steel with trivalent chromium zinc plating; 304 or 316 stainless steel for corrosive, offshore and washdown service.
• Every batch checked against the drawing with thread gauges before packing.

1. What an 8J Adapter Does

An 8J adapter is a JIC lock nut: a hexagon nut with a straight internal thread, made in the SAE J514 JIC sizes and used to secure a part that is sealed by another feature. It is not a tube nut, a plug or a conversion part, so no fluid passes through it and no seat is formed by it.

The part has two jobs. The first is to lock a bulkhead body against a panel, so the body cannot back out or shift when the tube nuts on either side are tightened. The second is to jam a stud against a boss face, where a straight stud has to be held at a fixed orientation while the tube assembly is made up.

That distinction matters, because the nut that completes a JIC 74° cone tube joint is a different part. The tube nut pulls the sleeve onto the tube and drives the cone into its seat, and in this catalogue it is ordered as NB200 with sleeve NB500 for metric tube or NB300 for inch tube. The 8J adapter never grips a tube and never loads a cone; it only clamps the body it is threaded onto.

The printed table describes the nut rather than a flow path: E is the thread the nut fits, A is the nut height and S1 is the hex across flats.

2. 8J Specifications

2.1 Connection 1 – the JIC thread the nut fits (E)

• Thread standard and family: SAE J514 JIC sizes, straight inch thread, in the SAE J514 JIC 74° cone family of hydraulic tube fittings.
• Thread size range available: 7/16″x20 to 2.1/2″x12, in the steps printed in table 2.5.
• Gender: female, one internal thread through the hex nut body.
• Sealing method: none in the nut. This is a clamping thread, not a sealing thread, and it is not made up against a taper.
• Mating part standard: the external thread of an SAE J514 JIC 74° cone stud end or bulkhead body of the same dash size, for example the 6J series bulkhead adapter or the AJ6JJ bulkhead branch tee.

2.2 Connection 2 – the panel, boss or face the nut locks

• Thread standard and family: not applicable. The second side of the nut is a flat bearing face and the hexagon itself, not a port.
• Size range available: the bearing face and hex follow the same eleven dash sizes as the thread, 17 mm to 70 mm across flats in table 2.5.
• Gender: not applicable. A bearing face and a hexagon are not male or female connections.
• Sealing method: none at this side. The nut clamps a flat face against a panel or boss, and sealing stays with the cone or O-ring of the mating part.
• Mating surface: the panel face or bulkhead bracket the body passes through, the boss face of a manifold, or a second nut in a jamming arrangement.

Connection 1 is the threaded side and connection 2 is the clamping side, so a buyer of the 8J adapter specifies the dash size once, from the E column of table 2.5.

2.3 Construction and Materials

The nut is machined from bar stock, with the thread cut and the hex formed in one setup so that the thread axis stays square to the bearing face. That squareness lets the nut clamp evenly instead of loading one side of a panel.

• Body material: carbon steel as standard; 304 stainless steel or 316 stainless steel on request; brass for selected sizes.
• Plating and finish: trivalent chromium zinc plating (Cr3+) for carbon steel as standard; zinc-nickel plating available. Plating thickness and corrosion performance are confirmed per order.
• Seal material options: none, because the lock nut carries no elastomer; NBR, FKM and EPDM apply to the elastomer-sealed components of the same circuit.
• Machining process: bar-stock turning and threading, with the thread produced to the mating part standard and checked against the drawing.
• Hex feature: one hexagon across flats, S1, from 17 mm at 8J-04 to 70 mm at 8J-32, with the nut height A running from 7 mm to 10.5 mm. There is no bulkhead feature and no bore in this series.

2.4 Pressure and Temperature

A lock nut is not a pressure-containing part, so no pressure value is published for this series. The pressure boundary of the joint belongs to the stud and its 74° cone seat, or to the O-ring of an SAE O-ring boss stud end, and the nut only has to hold that body in place. Working pressure for these sizes is confirmed per order by HENGHUA engineering, based on the thread size, sealing method and material selected.

Temperature is a material fact. For NBR seals the working range is approximately -30°C to +100°C; for FKM (Viton-type) seals approximately -20°C to +200°C; for EPDM seals approximately -40°C to +120°C. These figures describe the elastomer-sealed parts of the circuit, because the lock nut itself is steel without an elastomer.

Carbon steel with zinc plating suits general hydraulic service, including panel and bracket work inside machinery. Specify 304 or 316 stainless steel for corrosive, offshore or washdown environments, because a rusted lock nut can be impossible to remove without damaging the stem it locks.

2.5 Part Number and Dimension Table

The table below is the complete printed size range of the 8J series. Threads are printed in SAE notation, and all dimensions are in millimetres.

What each column means

• PART NO. – the HENGHUA part number. The prefix 8J means a JIC lock nut, followed by the dash size code. There is no second size code and no suffix in this series.
• E – the internal thread of the nut, printed as diameter x threads per inch in the SAE style, for example 7/16"X20. This is the thread the nut fits, not a port it connects to.
• A – the nut height, in millimetres, measured across the hexagon from one bearing face to the other, as marked A on the series drawing.
• S1 – the hex across flats, in millimetres, used to run the nut up with a wrench. The value steps with the thread size, from 17 mm to 70 mm.

Thread size and dash chart

The dash code is the size step and it follows the SAE convention of nominal tube outside diameter in sixteenths of an inch, so -04 is a 1/4″ tube size and -12 is a 3/4″ tube size. The printed thread and hex for each code are:

The nut height is not the same as a tube nut height, so check the A value against the recess the nut has to sit in.

3. How to Read an 8J Part Number

An 8J part number has two elements: the series prefix and one dash size code. The series does not use the geometry or sealing suffixes seen elsewhere in the range, such as -SP, -WD, -PK, -04 or -9, because this part has a single thread and no second connection.

The prefix 8J identifies the family: the lock nut of the JIC adapter range, threaded in the SAE J514 JIC sizes. A different prefix identifies a different part, such as the 6J bulkhead adapter that this nut locks, the AJ6JJ bulkhead branch tee or the 4J plug.

The dash size code carries the thread. Worked example: 8J-12.

• 8J – a JIC lock nut in the SAE J514 JIC thread range.
• 12 – the dash 12 size, which is the 1.1/16″x12 thread.
• From the table: the nut height A is 10.5 mm and the hex across flats S1 is 36 mm.
• The matching stem is a 1.1/16″x12 JIC 74° cone stud end or bulkhead stem of dash size 12, for example a 6J-12 bulkhead adapter or the stem of an AJ6JJ-12 bulkhead branch tee.

A buyer ordering 8J-12 therefore receives one hex lock nut with a 1.1/16″x12 internal thread, a 10.5 mm nut height and a 36 mm hex. Where the nut is ordered with the bulkhead body rather than separately, the catalogue marks the assembly with the suffix LN, as in 6J-12LN; the 8J nut is the lock nut supplied in that assembly and can also be ordered on its own line.

4. Installation and Fitment

A hydraulic fitting adapter of this type is assembled by hand and then tightened, never to pull two faces together. HENGHUA does not print a single torque figure for the series, because the correct tightening depends on the mating stem, the panel material and whether the nut is jamming against a boss or clamping a panel. Confirm the figure with HENGHUA engineering per order, or follow the recommendation of the supplier of the body the nut locks. Run the nut on by hand until the bearing face is snug, then tighten in stages without an extension bar.

Thread preparation: wipe the internal thread of the nut and the external thread of the stem clean, and remove any burr raised by a previous cross-threading. A light oil on the thread lets the nut run up smoothly. Do not wrap the thread with tape or coat it with a thread sealant as a leak cure, because this thread does not seal anything and sealant trapped under the nut only changes the clamp load.

Panel fit: the bearing face must land flat on the panel or bracket. Deburr the panel hole, keep paint and weld spatter off the seating face, and check that the hole diameter and thickness suit the body the nut locks. A nut tightened against a soft or oversized hole lets the body shift, and the shift shows up later as a weeping cone joint.

Jam arrangements: where the nut holds a stud at a fixed orientation, bring the stud to position by hand, then run the lock nut up against the boss face and tighten against that face only. Never use the lock nut to drive a cone or a boss seal into position.

Contamination control and reuse: keep the nut in its packaging until it is fitted, and cap open stems during storage so debris does not score the thread on first assembly. The nut is reusable while its thread and hex are undamaged; replace it if the thread has been crossed or the hex rounded by a worn wrench.

Common fitment errors and their symptoms:

• Using an 8J lock nut as a tube nut. Symptom: the tube is not gripped, the cone is never loaded and the joint weeps because no sleeve has been compressed.
• Running the nut onto a tapered pipe thread such as NPT or BSPT. Symptom: the nut jams after a few turns, the thread is torn and neither part can be reused.
• Fitting the wrong dash size. Symptom: the nut starts by hand but binds, or it spins freely because the thread diameter is too large.
• Tightening the nut against a painted or burred panel face. Symptom: the nut backs off under vibration and the body moves in the panel.

Six-step assembly

1. Confirm the part number against the line list and check that the nut thread matches the stem it is to lock.
2. Inspect the internal thread of the nut and the external thread of the stem for burrs, corrosion and previous cross-threading.
3. Clean both threads, and clean the panel or boss face the nut will bear against.
4. Run the nut on by hand until the bearing face is snug against the panel or boss.
5. Tighten the nut in stages to the recommended figure, holding the body steady so it does not turn in the panel.
6. Pressurise the circuit, check the tube side of the assembly for weeping, and re-check the nut after the first thermal cycle.

5. Applications and Industries

Application tags for the 8J adapter: hydraulic systems, water jetting, oil and gas, industrial equipment, construction machinery, agriculture, marine, material handling. A hydraulic fitting adapter of this type is specified by its thread and its role rather than by industry, so the same nut serves all of these sectors.

Bulkhead mounting through machine frames and cabinets. Whenever a hydraulic line has to pass through a frame rail, a tank wall, a cabinet panel or a fire wall, a bulkhead body is fitted through the panel and a lock nut secures it from the far side. The 8J adapter is that nut, and it keeps the bulkhead adapter square to the panel while the tube runs on both sides are tightened.

Repair and service. Lock nuts are lost, over-torqued or corroded in service, and one missing nut can leave a bulkhead body loose and a joint weeping. Because the JIC adapter range carries eleven sizes under plain dash codes, a replacement is picked from stock by thread size rather than made as a special.

OEM assembly lines. For production lines the nut is supplied to a drawing-based specification, with the material and plating fixed per programme and packed for line-side delivery to the correct station.

6. Replacement and Cross-Reference Guide

Cross-reference for this hydraulic fitting adapter series is organised by thread size and thread form, never by brand. Two lock nuts interchange only if the thread size, the thread form, the nut height and the hex all match.

The 8J series is the lock nut of the JIC hydraulic adapter family. It carries a straight inch thread in the SAE J514 JIC sizes and is a clamping part. It does not interchange with the tube nut that drives a sleeve onto a tube, or with a nut for a pipe thread. NPT nuts belong to a 60° taper thread under ANSI/ASME B1.20.1 and BSPT nuts to a 55° taper thread under ISO 7-1; neither will run correctly onto the straight JIC thread of a 74° cone stud.

To identify the correct replacement, measure three things.

1. Thread. Measure the outside diameter of the mating stem thread and count the threads per inch. A 9/16″x18 stem measures about 14.3 mm outside diameter with 18 threads per inch; a 1.1/16″x12 stem measures about 27 mm with 12 threads per inch. Record diameter and pitch together.
2. Thread form and type. Confirm that the stem thread is straight and parallel, not tapered, and that it is a JIC 74° cone stud or bulkhead stem rather than a pipe thread. A taper is visible as a diameter change along the thread, and forcing an 8J nut onto it destroys both threads.
3. Nut height and hex. Measure the nut height A and the hex across flats S1 of the part in hand, and compare them with the printed row. A nut of the right thread but the wrong height may not clear the recess above the thread, and a different hex changes the wrench size at the station.

Record the three measurements with the part number, and HENGHUA can match the replacement to the series and size code from the printed table in section 2.5. Where the nut is to be supplied with the body it locks, order the bulkhead body or bulkhead branch tee with the LN suffix so that the two parts arrive as one matched pair.

7. Ordering, Packaging and Delivery

To order, give the following information:

• Series code: 8J.
• Full part number, for example 8J-12, taken from table 2.5.
• Thread size, read from the E column, and the stem it is to lock.
• Nut height A and hex S1 required, if they differ from the printed row for that size.
• Body material and plating: carbon steel with trivalent chromium zinc plating, zinc-nickel plating, or 304 or 316 stainless steel.
• Quantity, destination and packing format.

Packaging formats: bulk cartons for line-side consumption, small boxes for distributor shelves and labelled bags for service kits, each labelled with the part number, the thread size and the quantity. Where the nut is supplied with a bulkhead body, the two are bagged together and the label carries the LN assembly part number.

Sample orders: validation samples and first-article parts are available for OEM programmes, including drawing-based manufacture of specials where the printed table does not cover the thread, height or hex required.

Lead time is confirmed per order, because it depends on the size, the material, the plating and the quantity. Send the requirement with the quantity and the required date, and HENGHUA confirms the schedule with the quotation. As a hydraulic adapter manufacturer and hydraulic adapter supplier, HENGHUA can quote the lock nut, the bulkhead body, the sleeve and the tube nut as one matched kit.

8. FAQ

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

A JIC 37° flare joint seals metal-to-metal on a 37° conical flare face under SAE J514. An ORFS joint seals a flat face against an elastomeric O-ring under SAE J1453. Neither changes the 8J lock nut, because this part seals nothing: it clamps a body already sealed by a cone or an O-ring. Choose the fluid family that matches the port on the equipment, then order the lock nut that fits the thread of that body.

Can NPT and BSPT be interchanged?

No. NPT is a 60° taper pipe thread under ANSI/ASME B1.20.1 and BSPT is a 55° taper pipe thread under ISO 7-1, so the thread form, angle and pitch differ and the two will not seal even where a size starts by hand. The question matters for this series in one specific way: the nut has a straight JIC internal thread and must never be run onto an NPT or BSPT stem.

How do I identify the correct 8J adapter size?

Measure the outside diameter and the pitch of the stem thread, then read across the E column of table 2.5 for that thread. When the thread matches a printed row, that row is the correct part number for the nut. Confirm at the same time that the stem is a JIC adapter stud or bulkhead stem of the same dash size, because the size code is what ties the nut to the body it locks.

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

This nut contains no elastomer, so there is no seal material to choose for the part itself. Select the compound for the elastomer-sealed parts of the same circuit: NBR for general mineral hydraulic oil in the range of approximately -30°C to +100°C, FKM (Viton-type) up to approximately +200°C or where the fluid attacks NBR, and EPDM for water and water-based fluids in the range of approximately -40°C to +120°C.

How is the working pressure of this part determined?

The lock nut does not carry the pressure boundary, so no pressure value is published for the series. Working pressure belongs to the stud and its 74° cone seat, or to the O-ring of an SAE O-ring boss stud end, and depends on the thread size, wall thickness, sealing method and material selected. Working pressure for these sizes is confirmed per order by HENGHUA engineering.

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

Minimum order quantity depends on the size code, the material and the plating, so it is confirmed with the quotation rather than published as one series figure. Samples and validation parts are available for OEM and distributor evaluation, including specials made to a drawing.

Is the lock nut the same as the nut supplied with a JIC tube assembly?

No. The nut that completes a JIC 74° cone hydraulic tube fitting is the tube nut, ordered as NB200 with sleeve NB500 for metric tube or NB300 for inch tube, and that nut drives the sleeve and loads the cone. The lock nut secures a body to a panel or jams it against a boss and never grips a tube, so the two are different parts even where the thread size is the same.

Send your requirement to HENGHUA

Send the part number, the thread size, the body it has to lock, the material and plating, and the quantity. HENGHUA confirms the match to the printed table and the delivery schedule, and quotes the 8J adapter as a single nut or as a matched set with the bulkhead body it secures.

Related series in the same family: the 6J adapter (bulkhead) and the AJ6JJ adapter (branch tee). Browse the full Hydraulic Adapters range for the complete SAE J514 JIC, NPT, ORFS and ISO 6162 flange families.