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The NBFK 4O hydraulic plug is a male SAE O-ring boss plug developed for sealing unused threaded ports in hydraulic equipment and fluid power systems.
Its design combines a straight male thread, an O-ring sealing element, and an external hexagonal section for tightening. The male thread engages with the corresponding female threaded port, while the O-ring provides the sealing interface between the plug and the port.
In an SAE O-ring boss connection, the sealing function is achieved by compressing the O-ring against the machined sealing area around the port opening. The threads provide the mechanical engagement that holds the plug in position, while the O-ring performs the sealing function. This separates the mechanical connection function from the sealing function.
The 4O series is suitable for closing compatible unused hydraulic ports during equipment assembly, maintenance, or system configuration. Its compact plug structure provides a direct way to close a threaded port without requiring an additional hose or adapter connection.
NBFK offers 14 thread sizes in the 4O series, from 5/16"X24 to 2.1/2"X12. Each model has a corresponding O-ring specification and installation dimensions. The available A, L, and S1 dimensions help users check the fitting depth and wrench clearance when selecting the appropriate model.
For correct installation, the port thread, O-ring size, and matching sealing geometry should be checked before use. The E thread end is specified in the supplied drawing as matching an ISO 11926-1 port.
SAE O-ring boss male plug design
Male straight thread connection
Integrated O-ring sealing arrangement
Designed for closing compatible threaded hydraulic ports
O-ring provides the sealing interface
External hexagonal section for wrench installation
Multiple thread sizes available
14 models listed in the product dimension table
PART NO. | THREAD | O-RING | DIMENSIONS | ||||||
| E | E端 | A | L | S1 | |||||
| 4O-02Z | 5/16"X24 | 6.07X1.63 | 7.54 | 15.2 | 12 | ||||
| 4O-03Z | 3/8"X24 | 7.65X1.63 | 7.54 | 15.2 | 14 | ||||
| 4O-04Z | 7/16"X20 | 8.92X1.83 | 9.1 | 17 | 14 | ||||
| 4O-05Z | 1/2"X20 | 10.52X1.83 | 9.1 | 17 | 17 | ||||
| 4O-06Z | 9/16"X18 | 11.89X1.98 | 9.9 | 18.5 | 17 | ||||
| 4O-08Z | 3/4"X16 | 16.36X2.21 | 11.1 | 20.3 | 22 | ||||
| 4O-10Z | 7/8"X14 | 19.18X2.46 | 12.7 | 23.6 | 27 | ||||
| 4O-12Z | 1.1/16"X12 | 23.47X2.95 | 15.1 | 27.7 | 32 | ||||
| 4O-14Z | 1.3/16"X12 | 26.62X2.95 | 15.1 | 27.7 | 36 | ||||
| 4O-16Z | 1.5/16"X12 | 29.74X2.95 | 15.1 | 28.4 | 38 | ||||
| 4O-20Z | 1.5/8"X12 | 37.46X3.00 | 15.1 | 30.5 | 50 | ||||
| 4O-24Z | 1.7/8"X12 | 43.69X3.00 | 15.1 | 32.3 | 55 | ||||
| 4O-32Z | 2.1/2"X12 | 59.36X3.00 | 15.1 | 36.3 | 70 | ||||
| Note: E thread end fit with ISO11926-1 port. | |||||||||
The 4O SAE O-ring boss plug is used to close compatible unused threaded ports in hydraulic systems and fluid power equipment.
Typical application areas include:
Hydraulic manifolds
Hydraulic valves and valve blocks
Hydraulic pumps and cylinders
Hydraulic machinery and equipment
Industrial fluid power systems
Hydraulic equipment assembly and maintenance
Closing unused SAE O-ring boss threaded ports
