I have a set of rotors, that were "just cut to 3mm"... the result is that the apex seal groove is offset to one side on every slot,add a straight cut corner seal to that mix, and you end up with binding seals , different compression ratios for each face, and a slight change in engine balance...
Really it should be done with some other measurements to exactly centre the groove, and those measurements need to come really off a brand new rotor, since the wear on a used will throw it off slightly, as you cut the seal slot wider, the vertical wall of the slot for the seal gets less as well, which means less sealing area of seal to rotor, and less wall to support the seal vertically, so the seal has a tendency to roll more than would a 2mm..
Its not impossible to do if you were a caring, diligent machinist with skill, but the average machinist I think will, and does, make a total **** up out of it.. I have not seen any milled rotors that were worth writing home about to date..max
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