Jim,
I suspect I'm not teaching you anything when I say that the flare tool has to match the seat, and there are 2 common sizes: 30 degree, and 45 degree (or is it 40?) Anyway, if you, like me, own several different flare tool kits, you can grab the wrong one or use the wrong side, and have mis-matched flares.
I agree with Don, though, that brake lines always use a double-flare. Brake line flare kits are available from most FLAPS. Or borrow one.
-Michael
