DO NOT make a Bubble ISO Flare using a Double Flare Tool - How to test a brake line flare

It looks close to a commercial bubble flare, but it doesn't seal.

Earlier last month, the brake light on my cluster seemed intermittent. It went away and the car and the brakes seemed fine. All of a sudden, that is after about a month, I found that the brakes became mushy, I really had to push the pedal to get it to brake properly. Once home, I opened the hood and saw that the brake fluid had been much drained from the reservoir.  Ironically, the brake light came on and off with the parking brake. The parking brake light, or brake light, was off with this unfortunate discovery.

Removing wheel by wheel, I found that the back of the driver side drum was wet. Not quite wet, but the corroded steel retained the leaking brake fluid. It was actually quite scary.

Unable to find a precut and flared piece of brake line at the right length, I bought a 25' coil of 3/16" steel brake line for $12 (CAD), the M10x1.0 flare nuts (about 1$ a piece) and forged ahead with the tools that I have. The results were disappointing.

The cutting wheel is not straight as the axle bolt became eccentric with use.
Lubrication and less pressure would avoid such an issue.
The cut line can be filed down.

There are instructions to make a bubble flare using general double flare tools, but I am not keen on watching videos on Youtube. ( Another video ) This is an excellent article on using the proper tools http://www.dcfiats.org/tech/Bubble_Flare_article.pdf , however I summarize my experience using a Double Flare Tool - it wasn't great.

1. Ensure that the tube is relatively straight coming out of the coil. The less the curvature the better.
2. Cut brake line with a tube cutter. I found that the mini tube cutter was not only dull, but difficult to use. Mine broke as I turned the cutting wheel in. A larger diameter cutter, with a deburring tool is best. The threads of the cutting tool pressure bolt, as well as the axle of the cutting wheel axle should be lubricated with a graphite based grease. 
3. Set the brake line in the anvil or clamp bar with the flat side up. (The reverse side of the flaring bar with a 45 degree chamfer. This kit (USA) is nice as the flaring bar as well as the yoke have a standard hex nuts allowing you clamp or flare using a ratchet.
4. Have the brake line protrude by 5.8mm or ¼ inch, the 4.75mm die depth is fine. Clamp the  nuts on the clamp bar. It may be necessary to use a wrench to properly tighten the bolts. 
5. Lubricate the die with brake fluid. Lubricate threads of the yoke with a graphite or a molybdenum based grease. 
6. Set the die on the opening of the brake line.
7. Set the yoke on the clamp bar and die and compress to create the bubble flare.

I followed the instructions in the videos and on http://1929fordhotrod.com/johnsblog/2011/04/27/iso-metric-bubble-flare-brakes-lines-easy/ however, almost all of my flares leaked. I tried with a new piece of line, straighter than the edge of crystal, but, I still could not get it to flare and seal properly.

It did not compress or mate well at all with the ISO union.
In addition to leaking when installed, it failed the test procedure as shown below.

I eventually gave up and bought an ISO flare tool. All the tools are the same, however this one, made in, the hyper industrialized and open society, Taiwan, does not feel that well made. On my first flare, the centering pin broke. The dies are made from soft steel, maybe equivalent to a grade 2 bolt. The double flaring tools are at least made with hardened steel.

I returned to the retailer to get a replacement. It went through my mind to bring a piece of line, a flare fitting, a union and a black marker to test it on the spot.

I got the impression that someone was either not maintaining the punching tools, asleep, or didn't care. The size marking could at least be in line with the die.

What I like about this tool are the hex heads for clamping and flaring.
The threads on the yoke and the compression bolt could be a little tighter. A finer thread would also ensure less angle distortion as the die compresses on the brake line.
My guess it is the yoke, however both cutting tools, tap, die, would make tighter threads with wear.

The flaring bar is electro-polished(I think) tool steel. My file could barely touch it. 

Flaring instructions

What the flares should look like. It would be good that the tools be sold with a gauge.
I am unable to measure nor guess the angle or the diameter of my flares.
A piece of steel or aluminum cut to profile could be used to ensure that the flare fits without too much play.

Neither look perfect, or even good for that matter, but a test will see.
I see them as off centre, uneven or lopsided bubble flares.

A combination of problems with this flare : (a) the clamp was uneven or not flat across both sides.
(b) tool marks or marring on the section flared made it that much worse.
Failure is the best teacher. Then again, it isn't good when our economy gives us the sense that we are one.

(Updated January 21st 2016)

How to test your flares

Using a black permanent marker, cover the contact surface of the flare.
The union on the left is used to test the mating surface.

Using line wrenches or regular wrenches, mate the flared line with a union. Somehow the nut is 12mm whereas the size of the union is 1/2". I tried the 13mm, but there was too much play. I imagine that is deliberate, as flare wrenches are sold in bundled metric/SAE sets. It could also be that the stock of union hex bar are all 1/2 and the individual pieces are then machined for various thread and flare types.

This is a little far, but compress the flare down. This image is from my attempt using the double flare tool.

Barely passable, actually, "If it isn't perfect, it isn't worth it!"
For this bubble flare test, I used the flat side of the flaring bar
like OTC Stinger 4504 and Neiko bubble flaring bars

Notice how the fitting or brake line nut flattens out the back of the bubble flare.

Left to right : A lot of pressure on the yoke (okay), less pressure (best)
and clamp bar flat side(not acceptable) to create the flares

Discussion

Seeing the different hand flaring tools available, I couldn't help but wonder why isn't there a different design for hand compression tools :

• A solid bolt whose thread fits that of the yoke - the bolt head is machined to the shape of the ISO bubble flare. The end of the bolt could be fitted with two nuts which lock against each other. A ratchet with the correct size could be used to compress the brake line in the correct shape. If the bolt has to be held in the lathe to make the female flare die shape, it will be centered no matter what.
• The use of a union or section of an old brake cylinder to form the bubble flare. Material mass and hardness may be an issue.
• Make dies of stronger material. A tube straightener could also aid the process. 
• Idiot proofing by designing the tool to require a flare nut to be on the line to make the flare?!

What would be better than designing a new tool? Local suppliers and retailers offer rentals or borrowing of properly working flaring tools, or if the value of the flare tool is too high, a flaring service. A hydraulic flaring tool may cost a couple hundred dollars, but it would ensure proper flares.

Another thing that comes to mind is a automobile service specialized in brake line repair. There are muffler shops, why not for brakes? Are there enough cars on the road that need new brake lines? Could the service be made more affordable? A database with the length of the brake lines of all automobiles so that the customer could come and have the lines quickly replaced?  3D drawings dimensions of  the brake lines - an automated bending tool to process the order for each vehicle? The parts are inexpensive - is it the labour, the insurance, the overhead? Should manufacturers be mandated to use copper nickel brake lines?

Links

http://www.garagejournal.com/forum/archive/index.php/t-88833.html

(It seems like I am not the only one struggling with the flares. I forgot about the work hardening of the steel line. After having broken my mini tube cutter, I bought a regular sized one. It cuts nicely after I lubed the threads and wheels, but it work hardens. I may have to try a rotary tool or hack saw - there are differing points of view on how to cut brake line.) 

http://www.jamesandtracy.co.uk/howto/Mercedes_E-class_replace_rusty_brake_pipes.html
This is an excellent write up on the replacement of brake lines.
The author is right to say that investing in copper nickel brake lines is the best choice. I found a coil to be about $50 CAD on Amazon.ca  - $18 in the USA. A coil of CuNi brake line is about $35 locally or $3 a foot at Canadian Tire - ($75 for 25'). CuNi brake line will also reduce the risk of breaking your flaring tools.
If you live in Canada, go to the parts desk of Canadian Tire to the get the fittings -most, but not all will be cheaper than from the rack. The M10x1.0 bubble flare nuts were $0.77 (part# FMS3028), the M12x1.0 were $2.58 (part# FMS3041 - my master cylinder has a different type of fitting than on the rest of the lines) - those prices were considerably cheaper than other shoppes that I checked out.  However, don't be surprised to find that your local shop, like CAPS, may even have better prices.
In the USA http://catalog.wdautoparts.com/ or Rock Auto.

http://advrider.com/index.php?threads/sealing-brake-bleeder-threads.900262/
I wish I had known about using pipe dope around the threads of a bleeder nipple. It would make it easier to bleed brakes. That would also prevent corrosion of the threads into the brake caliper/wheel cylinder

http://forum.ih8mud.com/threads/brake-line-flaring-procedure-questions.800370/
A good presentation from a newbie on how to make a double flare. Good points about the lubrication, and what a poorly formed flare looks like.

http://howtobuildhotrods.com/brake-lines-several-secrets-to-avoid-replacement/68/

http://www.thesamba.com/vw/forum/viewtopic.php?t=481299

http://www.dcfiats.org/tech/Bubble_Flare_article.pdf

http://www.fedhillusa.com/?page=tech2

http://www.fedhillusa.com/webnuts/common%20flares6.pdf 

http://www.slideshare.net/StanislavPliassounov/bus-case 

Notes
With no luck with either off the shelf tools, that is after my first ISO flare tool die broke, I went out and bought straight off the shelf flared brake lines with fittings. They were about 12cm too long, but I did manage. I saw the copper nickel lines, however, the flares were not very nice, nor did the walls of the lines seem uniform. Looking underneath the hood, the lines bear quite a bit of corrosion. I have to replace all the lines, but I may have to live with a pressure test for now. It was 20 degrees below freezing that morning. Another day was dedicated to install new brake lines.