when Ben says cut off one side of a butted tube, he is strictly referring to the seat tube. (Typically butted for about 150 mm or six inches, so the front derailleur does not squish the seat tube.) Most top and down tubes have thicker butting sections on both sides, and if you were to cut off all on one side you will end up with an end with no thicker butting. (thinner & weaker) up against the bottom bracket and seat tube. Personally, I use a hole saw for aluminum frames I build, and for small production steel I have been happy with using a bench grinder for mitering. Also it should be noted that a disc, or abrasive saw is right for cutting steel , since you would need a hack saw blade with about 90 teeth per inch as to not rip all the teeth off. good luck brian