Patent ID: 6993839

Claim:
A method for machining a stainless steel exhaust manifold for a multi-cylinder combustion engine, the exhaust manifold having a manifold body that includes a plurality of inlet tubes in fluid communication with at least one outlet, each of the inlet tubes having an inlet mouth and a coupling flange extending radially therefrom, the outlet having an outlet mouth and a coupling flange extending radially therefrom, each of the inlet coupling flanges having an interface surface adapted to mate with an engine block, and the outlet coupling flange having an interface surface adapted to mate with an exhaust assembly, the method comprising the steps of: supporting the manifold on a work structure; clamping the manifold to the work structure; and machining the supported and clamped manifold; the clamping step including the step of clamping each of the plurality of inlet coupling flanges separately; and the machining step including the step of machining the interface surfaces of the inlet coupling flanges; wherein the step of machining the interface surfaces of the inlet coupling flanges includes the steps of (i) a rough milling step that involves milling the interface surfaces of the inlet coupling flanges with a rough milling cutter, followed by (ii) a finish milling step that involves milling the interface surfaces of the inlet coupling flanges with a finish milling cutter; and during the rough milling step (i) the clamping step clamps at least certain of the inlet coupling flanges of the plurality of inlet tubes at a first clamping pressure, and during the finish milling step (ii) the clamping step clamps at least certain of the inlet coupling flanges of the plurality of inlet tubes at a second clamping pressure, lower than the first clamping pressure.