It may sound odd but plumbing is a big deal when building a hot rod. Engine building, welding, and fabricating are the glamor topics. But plumbing should be right there at the top. It is used on so many aspects of a build that it shouldn't be taken lightly and that means you should have the proper tools. Brake, fuel, and coolers are just some of the topics that come to mind that will require modest to exotic plumbing. Whether it is a single, bubble, or double flare or the gold standard—the AN- fitting—the proper tool can make this job easy and well done.

To get to the bottom of this, or how to make the proper tubing flare for each and every task at hand we rounded up an Eastwood brake tube flaring tool (PN 25304). It will allow you to make single, bubble, or double 45-degree flares. With the addition of Eastwood accessory 37-degree (PN 30005) flare dies you can now make flares ideally suited for AN- fittings—another widely used component in hot rod building.

First a little background.

Single Flare

Of all the flares, the single flare is the easiest to make. However, through repeated (generally less than four) uses they are prone to failure via splitting, galling, or deforming. It's because of this behavior that you will not find single flares used on brake lines (or you shouldn't!). There's one exception and that would be the AN- (for Army Navy) 37-degree single-flare fittings.

Bubble Flare

The first step of a double flare begins with a bubble flare and is strictly speaking a single flare. This bubble flare can be found primarily on British cars. American hot rodders typically don't use the bubble flare but for those restoring British cars the desire to do everything "according to the book" may be too much to ignore.

Double Flare

The double flare is used a great deal in American rodding and any hot rodder who has done his own brake lines has formed a double flare. It's achieved using a tool that first forms a "bubble" on the end of the metal brake line tubing, and then flattens the bubble in on itself. The double thickness of metal reduces the problems associated with a single flare. You will find those who know better recommend the use of a 45-degree double flare: the Society of Automotive Engineers and U.S. automakers.


It is not a good idea to use a single flare on brake lines. Double flare brake line connections are by far the most common and work ideally. Properly made and cared for, they work well in most applications. Double flares can withstand a number of repair cycles before they should be replaced. Bubble flares work well but require frequent replacement. AN- flare fittings are part of a system designed to meet military specifications. They're the "mack daddy" of brake line connections and designed to be used repeatedly without failure. All of us have seen, and probably used, AN- connections numerous times with our own hot rod builds. You will also see AN- used nearly exclusively on military and race car applications.

Eastwood Brake-Flaring Tool (PN 25304)

The Eastwood Brake-Flaring tool allows you to create three distinct flares, in any of five sizes of tubing and will do so quickly and accurately. (We might add after using this flaring tool it was also incredibly easy to use and yielded consistent and properly formed flares.)

The Eastwood flaring tool can fabricate 45-degree single, double, and bubble flares and it will work with stainless steel, steel, and soft metal tubing. This tubing can be used on anyone of these popular hot rod plumbing projects, such as brake lines, transmission cooler lines, and fuel lines. The turret-style indexed head keeps all flaring forming dies ready to use. (The PN 25304 comes with a 45-degree indexed head but there is an optional PN 30005 37-degree indexed head that will allow you to form flares for AN- fittings; a must of an accessory for the hot rod builder.) The quick-release T-handle screw clamp securely holds the tube-retaining dies. The tool comes with 3/16-, 1/4-, 5/16-, 3/8-inch and 4.75mm tube-retaining dies; T-handle; instructions; and case. The flaring tool is intended to be solidly mounted in a bench vice when used. The tool itself is made from forged steel, with durable, hardened-steel forming surfaces and dies, making this a tool that will be around for years.

The turret-style design allows you to make the appropriate flare in quick time. All the brake-flaring forming dies you need are mounted right on the turret. The T-handle screw clamp securely holds the die and tubing in place during forming.

According to the Eastwood instruction manual, and based on our use making lines for this year's Road Tour 1959 Chevy, we simply inserted the tubing, swung the turret to step 1 to set the proper line depth. Turn the turret to step 2, where we formed the flare. To form a double flare, spin the turret to step 3 to form it, all the while perfect alignment is maintained.

Follow along with the photos and you will see that making the proper 45- or 37-degree flare is truly as simple as 1-2-3.

Eastwood Tech Tip:
If you're in the middle of a restoration, wrap each aerosol can with 2 inches of masking tape and write what component it was used on—this will be very handy later on for touch-up.

Hot Rods By Dean
1 West Lone Cactus Drive
AZ  85027
Eastwood Company
263 Shoemaker Road
PA  19464
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