I have seccusfully double flared at 45 degrees nine different 3/16" stainless brake lines on my truck, with about 12,000 miles in two years I have had no problems.
All I have read on the subject reccomend the method I used for stainless brake lines.
There are two common types of flarred tube connections.
The 45 degree and the 37.5 degree.
45 is used with a single flare sometimes. For brake lines I belive, but am not sure, that a double flare is required by law in the US. Regardless of a law or not the 45 degree double flare is stronger, less likely to crack in the flare, and more likely to seal than a single flare.
The 37.5 degree flare is never double flared that I know of. It does require a backup sleve for better support of the flare in the fitting to reduce the likely hood of the flared part breaking off.
All materials can be flared either way.
I may not be 100% right about all this but I have tried to indicate where I am unsure.
There are some quite good profesional explinations out there on the web explaning the different types of tube connections and there uses. I suggest yall look them up before doing any sort of critical plumbing job like brake or fuel lines.
I'll try and post a link to a better explination when I find one.
Grigg
