Chassis and Frame Fabrication Technical

How To Form Perfect Brake Line Flares

Replacing brake lines or fuel lines is never fun. One of the most frustrating challenges of making new lines from scratch is getting a good flare on the end. And without a good flare, you’re practically asking for future leaks.

There are all kinds of tools to make flares, but the truth is most of them are awkward to use and fairly imprecise. Like most things, if you do these repairs every day you’ll develop a hand for it. But for most of us, we probably only make new lines every once in a while. So having a tool we can use that doesn’t require any particular muscle memory is a big bonus.

Eastwood’s professional brake line flaring tool is exactly the solution for amateurs as well as pros. Because it’s a vise-mounted tool that clamps the tubing in place for the process, it’s effectively foolproof to use. Both hands are free to concentrate on the flaring job instead of worrying about holding onto small-diameter pipes with one and a tool with the other.

Here’s how to use the tool. We’re using 3/16″ steel tubing in this case, but the tool comes with flaring dies that will also accommodate 1/4″, 5/16″ and 3/8″ as well as 4.74 mm metric tubing.

Step 1 – Cut and debur tubing

Using a tubing cutter, trim a length of steel, stainless steel or copper tubing to the length required for the job. Debur the ends of the tubing using the deburring blade built into the cutter. If necessary, straighten the last couple inches at the end of the tubing so it can rest in the forming die cleanly.

Step 2 – Select the correct forming die blocks

For each tubing size, there is a pair of corresponding dies. Each set of dies has two ends, one for forming bubble and double-bubble flares and the other for forming 45-degree flares. An optional 37-degree die set is available for making AN and JIC-style flares. Insert one of the die blocks in the forming tool facing up, with the correct flare end facing the rotary head on the tool.

Step 3 – Insert the tubing and close the die

Next, place the end of the tubing to be flared into the open die, leaving just a small amount (about 1/8″) of the tubing sticking out of the die. (You may want to install your fittings at this point while you still can). Now install the upper section of the die over the tubing, making sure the end of the die matches the lower half. Swing the locking bridge across the die blocks and lock into place with the locking pin. Snug the top clamp just enough to hold the die in place, but do not tighten yet.

Step 4 – Index the tubing

Spin the rotary head to face the tubing in the “OP.0” position. Pull on the lever arm to press the edge of the tubing flush with the die face. Now tighten the top clamp to lock down the die for final forming.

Step 5 – Make the initial flare

On the rotary head, find the “Step 1” position  for the diameter of tubing your bending and spin the head into position. In one movement, pull the lever arm until it stops. You’ve made the initial flare. If you’re forming a single-bubble or either 45- or 37-degree flares, you’re done and you can skip the next step. If you’re forming a double-bubble flare, you’ll need to perform one more step.

Eastwood's professional brake line flaring tool in use

Step 5.5 – Make the second flare (for double-bubble only)

Leaving the tubing locked in place, rotate the tool head to “Step 2” for your tubing diameter. Now make one more pull on the lever to complete the double-bubble flare.

Step 6 – Release the work

With the flare complete, release the pressure on the top clamp and release the locking pin on the bridge. Open up the die and lift the perfectly formed line from the tool. You’re done. Chances are this took only a few seconds to perform, saving you plenty of time for the tedious task or forming the line for installation in the vehicle. And there’s no one tool that does that job so easily.

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