To qualify as a “universal” leak stop plug, the seal must withstand a wide variety of standard industrial and automotive lubricants. Our 12*5mm end caps are injection-molded utilizing a high-density Nitrile Butadiene Rubber (NBR) matrix.

The structural integrity of this blanking cap relies on precisely calculated radial interference. The internal metal skeleton provides the rigidity necessary to prevent the cap from buckling or dishing inward under load. Simultaneously, the elastomeric coating compresses firmly against the 15mm housing bore. Because rubber behaves as an incompressible fluid when confined, this compression forces the elastomer into the microscopic machining grooves of the casting. This creates an absolute static lock that easily withstands internal gearbox splashing, thermal cycling, and high-frequency machine vibration.

Striking the center of the 15x5mm cap will cause the internal metal skeleton to “dish” or cave inward. This deformation instantly pulls the outer diameter away from the bore wall, completely destroying the radial interference fit and guaranteeing an immediate static oil leak. Technicians must use a flat installation mandrel that distributes force perfectly across the extreme outer edge of the seal. Additionally, wiping a very light film of system-compatible oil on the rubber OD prior to installation prevents the elastomer from binding, rolling, or tearing against the housing chamfer during the press-fit operation.