Wow....lots of uhh... "input" in this thread.... I do nothing but stainless steel brake, fuel and emission lines on my toys, customers cars , have done for decades, ......cheap steel lines are for the daily beaters....I have a KD double flare tool that I've used for decades, basic set using the small pin dies to create the double flare, I use a standard mini pipe cutter (Rigid) no heating or other voodoo to the cut ends other than using the deburring tool on the tubing cutter to deburr the inside of the freshly cut tube end, you need to learn just how much you need to insert in the tool (clamping jaws) to have just enough to create the double flare, takes some trial and error regardless of the tube alloy used, when I use the pin die to create the double flare, I just use white lithium grease to lube the line end/die....generally anything 1/4 inch up is fool proof in forming, however 3/16 brake line is a biotch to double flare, I generally have no problem flaring 3/16 diameter brake line with the KD flare kit, just that the 3/16 pin dies are only good for about a half dozen flares before the pin breaks off the die, so I generally bulk up on 3/16 pin dies when doing a vehicle..... just practice with some various techniques to see what works with your tool, if your not having success, perhaps it's the tool your using?

MikeG