An apparatus (10, 1010, 2010, 3010, 4010) for conveying a pressurized fluid (50, 1050, 2050, 3050, 4050) from a stationary source to an internal bore of a rotatable spindle shaft, while the spindle shaft is rotating, comprising: a fluid union housing (12, 1012, 2012, 3012, 4012) having first and second ends (70, 72, 1070, 2070, 3070, 3072, 4070, 4072) and an opening (16, 2016, 3016, 4016) extending therebetween along an axis (26, 2026, 3026, 4026), the opening defined by an internal wall, the first end (70, 1070, 2070, 3070, 4070) operatively connected, in use, to the stationary source and the second end (72, 3072, 4072) located, in use, proximate the rotatable spindle shaft; a fluid union shaft (20, 1020, 2020, 3020, 4020) located within the fluid union housing along the axis in alignment with the spindle shaft in use, and being rotatable relative to the fluid union housing, the fluid union shaft having an axial passage (44, 1044, 2044, 3044, 4044) with a first inlet end (52, 1052, 2052, 3052, 4052) and a second outlet end (54, 2054, 3054, 4054), the second outlet end being in fluid communication with the internal bore of the rotatable spindle shaft in use; wherein the fluid union housing and the fluid union shaft define an annularly shaped internal cavity (140, 2140, 3140a/b, 4140a/b) residing therebetween, such that when the stationary source supplies pressurized fluid to the first inlet end of the fluid union shaft some of the pressurized fluid flows into a first open end (142, 1142, 2142, 3142a/b, 4142a/b) of the internal cavity and continues flowing in an axial direction along the housing; an internal seal (200, 1200, 2200, 3200, 4200) located within the fluid union housing; and a discharge port (182, 2182, 3182, 4182) formed in the fluid union housing adjacent the internal seal, the discharge port adapted to permit outflow from the fluid union housing of pressurized fluid that has flowed along the internal cavity; characterized in that the internal seal is axially displaced from the first open end of the internal cavity, the internal seal preventing further axial flow of the pressurized fluid along the axis, and including first and second opposing annular surfaces (112, 1112, 2112, 3112, 4112, 206, 1206, 2206, 3206, 4206), with a first of the surfaces (112, 1112, 2112, 3112, 4112) being an abrasive material and a second of the surfaces (206, 1206, 2206, 3206, 4206) being a flexible lip of abradable material, whereby relative rotation of the first and second surfaces causes the abrasive surface to abrade the lip, such that portions of the lip deposit on the abrasive surface and become part thereof, and thereby resulting in an annularly shaped contact region of the like materials. a fluid union housing (12, 1012, 2012, 3012, 4012) having first and second ends (70, 72, 1070, 2070, 3070, 3072, 4070, 4072) and an opening (16, 2016, 3016, 4016) extending therebetween along an axis (26, 2026, 3026, 4026), the opening defined by an internal wall, the first end (70, 1070, 2070, 3070, 4070) operatively connected, in use, to the stationary source and the second end (72, 3072, 4072) located, in use, proximate the rotatable spindle shaft; a fluid union shaft (20, 1020, 2020, 3020, 4020) located within the fluid union housing along the axis in alignment with the spindle shaft in use, and being rotatable relative to the fluid union housing, the fluid union shaft having an axial passage (44, 1044, 2044, 3044, 4044) with a first inlet end (52, 1052, 2052, 3052, 4052) and a second outlet end (54, 2054, 3054, 4054), the second outlet end being in fluid communication with the internal bore of the rotatable spindle shaft in use; wherein the fluid union housing and the fluid union shaft define an annularly shaped internal cavity (140, 2140, 3140a/b, 4140a/b) residing therebetween, such that when the stationary source supplies pressurized fluid to the first inlet end of the fluid union shaft some of the pressurized fluid flows into a first open end (142, 1142, 2142, 3142a/b, 4142a/b) of the internal cavity and continues flowing in an axial direction along the housing; an internal seal (200, 1200, 2200, 3200, 4200) located within the fluid union housing; and a discharge port (182, 2182, 3182, 4182) formed in the fluid union housing adjacent the internal seal, the discharge port adapted to permit outflow from the fluid union housing of pressurized fluid that has flowed along the internal cavity; characterized in that the internal seal is axially displaced from the first open end of the internal cavity, the internal seal preventing further axial flow of the pressurized fluid along the axis, and including first and second opposing annular surfaces (112, 1112, 2112, 3112, 4112, 206, 1206, 2206, 3206, 4206), with a first of the surfaces (112, 1112, 2112, 3112, 4112) being an abrasive material and a second of the surfaces (206, 1206, 2206, 3206, 4206) being a flexible lip of abradable material, whereby relative rotation of the first and second surfaces causes the abrasive surface to abrade the lip, such that portions of the lip deposit on the abrasive surface and become part thereof, and thereby resulting in an annularly shaped contact region of the like materials.