AB Adapter – BSP Male 60 Degree Seat Tee

The AB adapter is a BSP male tee with three male stud ends, each machined with a 60 degree cone seat. One port takes the supply and the two remaining ports send the flow onward, so a single pressure line can feed two branches without adding a separate manifold block. Because every end is a male stud end with a metal-to-metal cone seat, the AB adapter is installed into female ports that already carry the matching 60 degree cone.

Choosing the right tee is not only a question of thread size. The branch port often differs from the two run ports, and the way flow splits between the two outlets changes the pressure available at each branch. This page covers the configuration logic, the complete dimension table, the sealing principle, installation practice and the questions buyers ask most often.

1. What the AB Adapter Does

A tee is a three-port fitting. In a hydraulic circuit it does one of three jobs: it divides one supply into two consumers, it combines two return lines into one, or it provides a take-off point for a pressure gauge, a pressure switch or a test point. This tee performs all three roles with male stud ends, which means the ports it screws into must be female ports with a 60 degree cone seat.

The sealing principle is identical on all three ports. The 60 degree cone on the adapter nose is pressed against the matching cone in the female port, and the two metal cones deform slightly at the contact band to form a seal. No bonded washer, no O-ring and no thread sealant is needed on a correctly machined 60 degree seat, provided the torque is correct and both cones are clean and undamaged. The cone angle and the surface finish of the cone therefore matter as much as the thread designation.

Because a tee is a single body, the branch flow passes through an internal intersection. That intersection is the point of highest local velocity in the fitting. When one branch is much smaller than the run, most of the flow is forced through a short reduced section and the pressure drop across the tee rises. Buyers sizing a tee for a high-flow line should therefore check the branch bore, not only the thread size.

2. AB Adapter Specifications

2.1 Product Scope and Configuration

The range covers equal tees, where all three ports share one thread size, and reducing tees, where the branch port differs from the two run ports. In the reducing part numbers the first and third numbers are the run ports and the middle number is the branch port, so the three-port layout is symmetrical about the branch. Both configurations use the same body style and the same 60 degree cone seat on every end.

2.2 Materials and Surface Treatment

Standard supply is carbon steel with zinc plating for general hydraulic service. Where the fluid, the wash-down regime or the outdoor environment is aggressive, 304 stainless steel or 316 stainless steel is used instead, and brass remains available for lower-pressure industrial and instrument lines. Plating options include trivalent chromium zinc (Cr3+) and zinc-nickel for a higher corrosion demand. No salt-spray hours and no plating thickness figures are published on this page; the current test report should be requested from the supplier before a specification is frozen.

2.3 Threads, Standards and Sealing Principle

The three thread columns in the table are labelled E, F and G. E and G are the two run ports and F is the branch port. All threads are BSP parallel threads to ISO 228-1, and the seal is made by the 60 degree cone seat rather than by the thread, so the thread itself does not need a sealant. This is the classic BSP 60 degree seat interface used across hydraulic power units, and it should not be confused with a taper thread joint, which seals on the thread flanks.

2.4 Dimensions and Part Numbers

All dimensions are in millimetres. A and C are the two run-port lengths (ports E and G), B is the branch-port length (port F), and S1 is the across-flats size of the body. On an equal tee A, B and C are identical; on a reducing tee the branch dimension B changes with the branch thread size.

2.5 Working Conditions and Limits

The usable working pressure of any 60 degree seat fitting depends on the thread size, the body material and the strength of the female port it is screwed into, so no single figure covers the whole range. For a specific project, state the fluid, the working pressure, the peak pressure, the temperature range and the vibration environment, and the supplier will confirm the appropriate material, plating and torque values. Carbon steel with zinc plating suits general mineral-oil hydraulic service; stainless steel is the usual answer where the fluid or the atmosphere is corrosive.

3. Part Number Decoding

The part number is built from the port sizes, written in the same order as the thread columns E, F and G.

• AB-06: an equal tee, all three ports G3/8″X19.
• AB-06-08-06: a reducing tee, run ports G3/8″X19 (E and G) and branch port G1/2″X14 (F).
• AB-12-16-12: run ports G3/4″X14 and branch port G1″X11.
• AB-32: an equal tee, all three ports G2″X11.

Read the number as run – branch – run. A single size code means the tee is equal. Three size codes mean the tee is reducing, and the middle code always describes the branch that faces away from the run axis.

4. Installation and Fitment

A 60 degree seat joint is a precision joint, and a few simple habits keep it leak-free.

1. Confirm that all three female ports are machined with a 60 degree cone seat. A parallel BSP port without a cone cannot seal against this adapter.
2. Inspect every cone before assembly. A burr, a scratch or a paint spot on the cone will produce a weep that no amount of tightening will cure.
3. Clean the threads and the cones. Blow out debris rather than wiping it into the seat.
4. Start each port by hand to avoid cross-threading, then tighten in three stages so the body is not twisted.
5. Support the branch line. The fitting should not carry the weight of a hose or a heavy component.
6. Re-check the tightness of all three ports after the first heat cycle.

When the AB adapter is used to feed a gauge or a test point, the branch port can be fitted with a plug or a test coupling so the line can be checked without breaking the main connection.

5. Applications and Industries

Typical applications include:

• Mobile hydraulics: splitting a pump outlet between a steering circuit and a work function.
• Industrial power units: feeding a gauge line and a return line from one manifold port.
• Test benches: providing a permanent pressure take-off with a plugged branch.
• Agricultural and forestry machinery: distributing flow to two cylinders on the same implement.
• Marine deck machinery: stainless steel versions where salt exposure is continuous.
• Mining and material handling: heavy-wall fittings in high-vibration installations.
• Machine tools and press equipment: compact branching inside a confined valve stack.

6. Replacement and Cross-Reference

When replacing an existing tee, work from measurements rather than from a colour code or an old marking. Record the three thread designations, the number of ports, the across-flats size S1, and the port lengths A, B and C. A replacement is equivalent only when the thread family, the seat angle, the port layout and the overall envelope all match. If the original part carries an unfamiliar number, measure the thread with a pitch gauge, check the seat with a cone gauge, and send the drawing or the measured values for confirmation.

Because the 60 degree seat family is used by many hydraulic systems, a tee can often be replaced by a different body style, for example a tee with a branch that accepts a swivel nut. That decision should be made on the circuit drawing, because changing the branch interface also changes the sealing method.

7. Ordering, Packaging and Delivery

To place an order, provide:

• the part number, for example AB-08 or AB-06-08-06;
• the three thread designations, in E, F, G order;
• the material and the plating option;
• the quantity and the required delivery date.

Parts are supplied individually protected and packed in bulk cartons or in kit bags, with the part number marked on the bag or the label. Minimum order quantities, carton quantities, marking and traceability requirements, and lead times are confirmed at the quotation stage, and special packing or kitting can be arranged for OEM programmes.

8. Frequently Asked Questions

Q1. What is the difference between the AB adapter and a BSPT tee? The parallel seat version seals on a 60 degree metal cone seat and uses BSP parallel threads, so it needs no sealant and can be re-used many times. A BSPT tee seals on taper threads, must be assembled with a thread sealant, and deforms the port thread slightly each time it is tightened.

Q2. Can this style be installed into a BSPT female port? No. A taper female port does not present the 60 degree cone that the adapter nose needs, and the two thread forms seal by different principles. Use a taper-thread product for a taper port.

Q3. Do I need a sealing washer on the 60 degree seat? No. The joint seals on the cone. Adding a washer moves the nose away from the seat and usually causes a leak.

Q4. How do I choose between an equal tee and a reducing tee? Choose an equal tee when all three lines carry the same flow and use the same hose or tube size. Choose a reducing tee when the branch is a small take-off, such as a gauge line, or when the two branches are deliberately different sizes to balance flow.

Q5. Does the branch reduce the working pressure? The branch itself does not set a pressure limit, but the reduced bore creates a local pressure drop and higher velocity at the internal intersection. On a high-flow line, select the branch bore so the pressure drop stays inside the system allowance.

Q6. Which material should I choose for a marine application? 316 stainless steel is the usual choice for continuous salt exposure. 304 stainless steel suits many wash-down applications, and carbon steel with zinc-nickel plating is used where the environment is controlled and the cost target is tight.

Q7. How do I measure an unknown tee so I can order a replacement? Measure the outside diameter and the pitch of each thread, confirm the seat angle, then measure the across-flats size and the three port lengths. Send these values with a photograph and the supplier can identify the equivalent part.

Q8. Can the AB adapter be used as a cross? No. A cross has four ports and a different internal geometry. Use a four-port body when four lines must meet at one point, and use a tee when a line must be divided into two.

Browse the full Hydraulic Adapters range for the complete family, or contact us to request a quote, mill test reports, and samples.