Even though I posted advice about how to grind the end of the housing square square, the face is that it isn't necessary if a decent cut is made with a cable cutter. It won't be perfectly square, but that's OK because a decent ferrule will take care of it. 99.9% of bikes, including the top end stuff ridden by the pros are put together with housings that weren't ground square, and work perfectly well.

All this obsessiveness is really a case of gilding the lily. If the newly cut housing is that far off, you don't need a grinder, you need a decent cable cutter.