Abstract: A small diameter high pressure liquid spray nozzle assembly has a small diameter elongated cylindrical body with a tubular nozzle shaft rotatably supported within the body. A stack of several identical radial ball bearings within a sealed bearing chamber in the body rotatably supports the shaft. The ball bearings are immersed in said chamber in a viscous liquid to provide viscous damping to retard speed of rotation of the nozzle shaft. A rotary high pressure liquid sealing assembly within the body between a high pressure liquid inlet to the body and an inlet to the shaft confine the flow of high pressure liquid to a flow passage within the body isolated from the interior of the bearing chamber. The viscous damping retardation is independent of the direction of the rotary nozzle shaft.