May 03, 2011· How to machine a hollow sphere I'm looking at a job to machine a hollow sphere. The outside is 4" in diameter and the wall thickness is 1/4", so the insided diameter is 3 1/2". There are two holes 1 1/2" in diameter where a tubes are to be welded on both sides (the two holes are opposite each other). The material is stainless steel.
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