Use an abrasive wheel on a Dremel tool to make the cut, then clamp the tube into a flaring tool backwards to its normal direction and use the back side of the flare block as a guide to square up the cut with a file. Be aware you'll have to double-flare any steel line you fabricate, brake or fuel lines. Trying to single-flare steel tubing results in a leaky joint and/or a cracked flare.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!