Automotive and HVAC tubing flares are 45 degrees. Aircraft flares are 37 degrees. The forming tools must be hardened or they gall.
Here is a tip, use reloading case lube (lanolin). It makes the job easier and delivers a better sealing surface.
Steve

wrote in message ...
One of the steel brake lines corroded enough that it started to leak.
So I need to replace a section of the line. Somehow it is something
that I have never had to do before and do not have the tools. But I
looked on the internet and found descriptions of how to do it and lots
of discussion on RCM on problems one can have.

But what I did not find was anything about how to make the adapter
used to make double flares. Have a lathe, should be trivial to make
the double flare adapter.

In searching I found the Lisle sells the adapters. Naturally none of
the autoparts stores carries the Lisle 31370 part, but found a bunch
of mail order places that do carry it. Most of them sell the part at
discount, but with a big shipping charge. The best total cost I found
was Auto Parts 123 selling through Amazon. $2.18 for the part, and
$5.23 for the shipping. Note this only is worthwhile if you already
have a tool for single flares. After I get the part, I will try to
post something so that others can make their own.


Dan