“Zero Tolerance Machining”

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How is it that the metal appears to be entirely seamless once two pieces are put together in a “Zero Tolerance” situation? It’s mezmerizing and mind boggling to me!

In: Engineering

Zero tolerance machining is a bit of a misnomer, it really is just any form of machining with incredibly low tolerances. Parts manufactured by Electronic Discharge Machining (EDM), usually the ones you are describing, can have dimensions accurate to the millionth of an inch scale.

EDM involves a wire or electrode brought close to a part underneath a bath of dielectric fluid. At very high voltages a spark can travel a precise distance to the nearest location on the metal part and vaporize a small piece that the fluid carries away. Repeat this process a lot and you can remove enough metal to produce the part you want accurate to a millionth of an inch. Do it twice to make parts that fit together and you get what you have described.