Abstract: A drill bit assembly has a housing having a central passageway including a pressure chamber and a vacuum chamber. The pressure chamber is connectable with a pressure source and the vacuum chamber is connectable with a vacuum source. The pressure chamber and vacuum chamber are in fluid communication with each other. A bearing assembly has an outer race rigidly mounted within the pressure chamber and an inner race for frictionally engaging the drill bit. A bracket mounts the housing with the drill bit extending through the central passageway. A seal is formed between the pressure chamber and the vacuum chamber as fluid, such as air, from the pressure source flows into the pressure chamber to the vacuum chamber for exhausting to the vacuum source.

Abstract: A method of manufacturing a moulded part using a first and second mould, wherein the first mould has a complementary design of the outer surface of the moulded part and the second mould has a complementary design of the inner surface of the moulded part and a boss cavity for forming an outer wall of a thin-walled boss to be moulded onto the inner face of the moulded part. The steps include seating a plug substantially co-planar with the complementary inner surface design and extending the plug into the boss cavity presenting an inner wall of the boss, wherein the thickness between the inner and outer wall of the boss is less than 60% of the thickness of the moulded part where the boss is moulded thereto. Closing the first and second mould forming a mould cavity. Injecting molten material into the mould cavity. Waiting a predetermined amount of time to allow the molten material to harden. Opening the first and second moulds. Extending the plug from the boss cavity.