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Inline Tube - Tips For A Perfect Flare

What should I use 45 or 37 degree flares
There are many different plumbing systems available, and which one is right for your application? We are going to talk about the 3 most common: Inverted Flare, -AN and Pipe.

Inverted Flare or 45 is on all standard automotive applications, cars and trucks from the 30's to mid 80's have inverted flare fittings at all the connections. Inverted flare is a single nut that uses a 45 degree double flare. This flare is lapped over so the tube is double thickness at the end. A inverted or double flare has a tube nut that pushes the flare against the brass seat to make a leak proof connection. For a leak to stop the flare it must seal against the brass seat. Using Teflon tape does no good because the thread is not what seals the line to the flare. The tape seals the thread but the fluid will still leak between the tube and the hole in the fitting. When sealing newly flared lines to old components the line must be tightened then loosened and the process must be repeated until the leak stops. If component brass seat is used, you are trying to seat over the existing crush ring, this may take a few tries but repeating the process will form the line flare to the brass seat. To form the end of the tube it requires a 45 degree double flare tool. Inverted flare fittings and tools are always less expensive because they are more common.

-AN or 37 is short for army/navy standard this system was never used on new cars from the factory. The -AN system was used on military equipment and introduced into the auto aftermarket in the 60's. The -AN fittings are a two part fitting part, one is a nut and part two is a sleeve. The nut holds the sleeve and tube in place. Since -AN uses a 37 degree single flare a sleeve is required to give extra support to the flare. This single flare can leave a rough edge to the tube since it is not rolled over. Since -AN fittings were never used on factory applications a adapter fitting must be used on any factory master cylinder or proportioning valve. So instead of having one fitting into the master when using inverted flare there will now be a nut, sleeve, and adapter. The down side is that there are now three connections and the cost of three fittings. To form the end of the tube it requires a 37 degree single flare tool. -AN flare fittings and tools are generally more expensive because they are less common.

Pipe is a tapered thread that uses the thread of the fitting to seal against the thread wall of the component. Teflon tape is used at this connection because the threads are sealing the part. All tapered fittings are pipe and require tape. Pipe fittings can also be seen on factory cars, some fuel pumps, and other components use pipe thread. Most after market parts: residual valves, adjustable valves, aftermarket calipers, thru frame fittings, and etc are made using pipe thread. Pipe thread is a universal system designed to work with all systems. Pipe thread is used to connect different systems. Pipe adapters are made for both -AN and inverted flare.

The problem with all these systems is it's like different languages and -AN is one language, inverted flare is another language, and pipe is the translator. Pipe works with both but -AN and Inverted flare do not work together.

If you choose to use -AN you will have a 37 degree flare and if you choose Inverted flare you will have a 45 degree double flare. The double flare is a stronger flare but more difficult to make. Both of these flares can be formed on stainless as well as tin steel tube. Knowledge and practice make a perfect flare. We have outlined the steps in the process for both tools. By following these steps you will achieve a perfect flare every time.



Use the right tube
Not all tubing is the same, there are many grades and thickness. This makes the difference in being able to flare the tube. Automotive tubing is .028 wall thick.  Thicker tubes .035 and .048 are a nightmare to bend because they are thicker. The thicker tube also reduces the inside diameter so your brake fluid flow is restricted. 
Steel Tube: has a tin coating for corrosion resistance. The heating process of the tubing for the coating causes the tube to be hard or soft. Also depending on what the tubing is made for it can be single wall or double wall tube. On single wall tube the weld seam is clearly visible and this tube will be cheaper and much harder to work with (Not worth it). Double wall tube is much softer and there is no seam. Some steel tube has no coating and while it saves money it will rust almost right away. Inline Tube uses the best tube on the market, it is doubled wall with a tin coating on the outside and a copper coating on the inside made to automotive specifications to be effortless to end form and bend. Tubing has many uses and general tube from the supply house has general specifications. Inline Tubing is specifically for automotive use and ordered to your specification.
Stainless Tube: has many benefits. It will never corrode and it has a bright glossy finish that can be polished to chrome but requires a better tool to flare. This tubing is also on the market in many different grades, thickness, and hardness which all play a role in how hard it will be to flare. General tubing can be very hard to flare and the finish may not hold up depending on the composition of the tube. Inline stainless tubing is 304 grade, 028 fully annealed, with a bright finish. This all means that it is the easiest to to work with on the market.



Use the right Tools
Not all tools are the same, the cheap $25 dollar tool is designed for copper tube and barley gets the job done. In tools you get what you pay for.  A good flaring tool can cost between $65.00 and $110.00. Good tool names are Ridge, Blue Point, Imperial Eastman, and Inline Tube carries them all. 



Prep the tube 45 degree
Cut tubing with a wire fiber wheel not a tube cutter. The fiber wheel is a clean heat free cut and it is fast. The tube cutter heats up the end causing work hardening and also roles the inside edge in making it very difficult to flare. Once the tube is cut it will have a burr on the inside and outside of the tube, this burr must be cleaned off. To take care of the outside we use a flat file working a 45 angle around the edge of the tube. For the inside edge we use a drill, center drill, or chamfer bit.


Ready for flaring 45 degree
Once the tube is prepped the end will come to a point. By removing material from both the inside and the outside edge the tube will fold over much easier when we begin flaring.


Measure the tube 45 degree
Advance the tube through the die block so it is at the same height of the lip of the button. The proper distance for the tubing to be raised above the die block is gauged by the head of the appropriate button. The second ridge for the 3/16 button is used. Make sure the tube is advanced flush with the top of the button. Use the side clamp to hold the tube and it can be helpful to clamp in a vise to hold the tool. Now place the button with the pin in the tube and line the tool over the top of the button. With the tube clamped start turning the top handle until the button die reaches the die bar. You will feel the tube forming as you are turning. DO NOT OVER TIGHTEN the tool. When the button die is at the die block you are done. If the tool is over tightened the small button will usually fail by cracking into two. If you are unsure stop early.  This is considered the first operation of the double flair.



 

Do not over tighten 45 degree
Now place the button with the pin in the tube and line the tool over the top of the button. With the tube clamped start turning the top handle until the button die reaches the die bar. You will feel the tube forming as you are turning. DO NOT OVER TIGHTEN the tool. When the button die is at the die block you are done. If the tool is over tightened the small button will usually fail by cracking into two. If you are unsure stop early.  This is considered the first operation of the double flair.



 

Let the tool do the work 45 degree
Remove the small button die and tighten the handle again, this will fold over the tube to form a smooth uniform flare. Loosen the tool and take a look.  This is considered the second operation of the double flair.



 

Inspect your flair 45 degree
This basically shows the three operations. Cut and debur your tube, first operation, second operation and you are finished. Now inspect your results. There are many thing that can go wrong so if you do not have a perfect flair with the tips below try again.

Tube Cutting - Do Not use a tube cutter. Cut the tube with a fiber wheel or metal cut off saw.

Prevent Tube Slipping - If your tube is slipping from the tool you may clamp it in a vise or clamp the opposite end with vise grip pliers.

Shallow Flairs - Are a result of not allowing enough material to stick up through the die block. The proper distance is measured to the top of the button. This distance may vary so if the flair is shallow advance more tube, and if the flare is too much lower the tube, this height may vary on different size tubing.

Die Cracking - The buttons for the double flair should never be tightened against the die block. If this occurs the button will crack. DO NOT OVER TIGHTEN THE TOOL. This button may also break if not enough tube is advanced thru die block and button bottoms out.

A Final Note - Fairing tube takes practice and an understanding of how the tool works. Once the practice is put in the understanding will come. Read the instructions before starting, they will save you lots of time in the end.



Prep the tube 37 degree
Cut tubing with a wire fiber wheel, not a tube cutter. The fiber wheel is a clean heat free cut and it is fast. The tube cutter heats up the end causing work hardening and also roles the inside edge in making it very difficult to flare. Once the tube is cut it will have a burr on the inside and out side of the tube, this burr must be cleaned off. To take care of the out side we use a flat file working a 45 angle around the edge of the tube. For the inside edge we use a drill and a center drill or chamfer bit.


Ready for flaring 37 degree
Once the tube is prepped the end will have a chamfer on both the inside and outside edge. You want the end of the tube to be as flat as possible with no burr.  If the end of the tube is not prepped when a flair is applied the edge will be rough and dig into the component.



Measure the tube 37 degree
Advance the tube through the die block so it is at the same height of the block. This is the same for all sizes of tube. Use the side clamp to hold the tube and it can be helpful to clamp in a vise to hold the tool. With the tube clamped start turning the top handle until the handle pops and spins with no effort. You will feel the tube forming as you are turning. You can not over tighten this tool once the cone reaches the die block it pops and you are done. This tool has a off set head so it works the edge of the tube out slowly for a perfect flair.



Inspect your flare 37 degree
This is a single flare so if it is shallow advance more tube up through the die block and if it is too big reduce the amount of tube though the block.  Since tubing varies so will this height. It will take a few times before it is just right. Since the single flair has a rough edge you may want to file any burr off the edge before installing.


Consult your mechanic
This page is intended for use as a basic guide to help install new brake and fuel lines. If you are unsure about any part of the installation procedure, please consult a certified professional mechanic for assistance. Inline Tube assumes no responsibility or liability for improperly installed lines. 


Quick Tip: Tube Flaring

Read the instructions - Stainless and steel tube flair the exact same way. The steel tube is a bit softer and this makes it easier to flair but if you follow the steps the stainless will come out just as nice.


Sources:

Inline Tube - Brake & Fuel Lines

15066 Technology Drive
Shelby Twp, MI 48315
(586) 532-1338

www.Inlinetube.com