Magnum Exh manifold machining.

Cuda416 said
I have an idea what might work. Thinking about the flattening jigs woodworkers use for getting a table top or other surface flat using a hand router. Basically they build a movable gantry/carriage in which the router sits, then they simply place it over the work piece and pass the router over a billion times and end up with something that matches the plane of the carriage.

I could mount a 4" grinder onto a carriage like that and as long as everything is locked into place, just keep sliding the grinder back and fourth until the material is removed. Like a hillbilly surface grinder.

-=C

Stranger things have been done, it could work. You should be able to hog most of the material by hand and use the fixture for the last bit, but it will take some time and you'll have to nibble at it. I've seen guys grind hardened lathe ways by mounting a grinder on a sled and running it up and down the less worn tailstock ways. Those jobs ended up at a couple tenths of thousandths over several feet.