One dreaded job when working on anything with a motor, especially when doing a restoration, is working on the brake and fuel system. It's a tedious job, and often times messy. My biggest fear is probably the same as yours, you build a car, take the time to put new parts everywhere, new paint, etc, and you then flare new brake and fuel lines. When the time comes, you fill the system with fluid (or fuel), and when pressurized, you can only hope and pray one or more of your fittings don't leak. It's the WORST when they do, and only makes the job that much more tedious and messy.
You can eliminate leakage at the hardline fittings by taking a few essential steps to assure you have clean, uniform flares at each fitting. The biggest thing is to make sure you are using a quality tool that can perform metric DIN flares or "bubble flares". Not all tools are made to do this, and many require a 2-step process to produce them, which means more chances for error when making flares. I used to prefer the high end hydraulic flare tool by Snap-On, and after some practice, it too made really nice flares, but the 2 gripes I had with it was that you could first "overflare" the line. This is because it is a hydraulic system where you just pump the cylinder and you can't really feel much resistance; therefore you can easily flare the line so much it's deformed. Secondly, it required changing the dies which turns the job into a 2 step process. I like simplicity, and this wasn't it.
Here at Eastwood we have a compact Professional Brake Tubing Flaring Tool that will make most any flare you will commonly come across. I decided to cover one of the less-common types of flares that's often difficult to perfect. With this tool it makes the job a simple one step process that you can be assured won't leak.
The next most important thing to do when making flares in tubing is to use a tubing cutter with a sharp cutting wheel that isn't chipped or deformed.
Using a cut off wheel is also a recipe for leaks if you aren't extremely careful. A leak can start from the moment you cut the line to flare it. You NEED a straight, clean cut on the tubing so the flare can be uniform in shape. Also you can't always trust that the end on your brand new roll of brake line is straight. Even the factory can cut it uneven, and that can cause a subpar flare. Below I demonstrated a poor bubble flare on a piece of unevenly cut 3/16 brake line, next to a straight cut, properly formed bubble flare. Notice how the flare on the left has a line where the end of the tubing wasn't completely formed on half of the flare? That's because that side of the line was low from an uneven cut, and it wasn't properly flared. That fitting WILL LEAK.
Now that you've gotten your tubing cut square, you are ready to clamp the tubing into the flare tool. Since I was working on an older European car (VW Rabbit) with bubble flares, I chose the die with the "DIN" stamp on one end, and rotated the head of the tool to the matching DIN setting. From there I placed the bottom half of the die into the tool with the "DIN" stamping towards the head of the tool.
Next you want to set the brake line into the bottom half of the die, and make sure that the end of the brake line is square and flush with the "DIN" end of the die. From there you will install the top half of the die, flip the clamp down, install the pin in the clamp, and tighten the clamp until the die halves are firmly clamped together (we don't want that line wiggling back in the die!). Also be sure to lube the brake line up where you will be forming the flare. Some use copper anti-seize, others grease, but I go the simple route and spray some spray lubricant like WD-40 on the line.
Once your line is clamped and lubed, you simply pull the lever on the flaring tool in one steady motion until it "stops" (just about 90 degrees I found). One nice feature is that the tool has a definite point where it "stops", and I could easily tell when the flare was fully formed. It's as simple as that! Just remove the clamp on the die, the top half of the die, and then the brake line, and you are ready to install on the vehicle!
Below you can see an example of a flare I produced with our Professional Brake Tubing Flaring Tool versus an original flare off of the car. One of these flares could be made in literally under a minute, it makes doing a brake line job so much easier, and the tool pays for itself almost instantly!