I have an old Superior 200 flaring tool someone gave me. It's just like all the other cheap ones except the face on the yoke where it contacts the die block is milled flat. I was missing the dies for double flares so I bought a cheap one at Autozone just to get the dies. I just replaced all the brake lines on my '41 with copper-nickel. I didn't have any problem making flares as long as I was careful to get everything lined up. I tested the lines with air pressure before adding fluid, had 2 or 3 that leaked but stopped when I tightened a little more.
