Folks,

I bought a Rigid 45 deg double flare tool. I will be fabricating some new brake hard lines soon. I'll probably use 27 deg AN-3 for anything not specifically requiring the SAE double flare.

I want to practice make flares, but would like to test them in some way.
One way I've thought of is to screw the male fitting into a cap, then pressurize the line with compressed air and put it in a bucket of water to look for bubbles.

However, that will only achieve 110 psi or so, and brake system pressures can be higher than that.

Has anyone else ever experimented with this?

Thanks,
Gustave

 

Not with brake lines but I have tested other tubing networks up to 3000 PSI. A hand powered grease gun will do that quite easily. Plug off the end (try and use a high pressure gauge as the plug) fill the tube with water then pump up (using the grease gun) to I would say 500 psi and see if the pressure holds or water leaks out of your fittings. If pressure won't hold and you get no leaking water then I would suspect your grease gun is leaking back.
The reason you fill the tube with a liquid is a liquid is not compressable where a gas is. If you used a gas it would compress and if there would happen to be a rupture the gas would expand rapidly and possably hurt someone with flying debris. A liquid on the other hand will not compress and in the event of a rupture the only thing that will happen is the liquid will escape to the atmosphere.

 

Close examination of the flare should tell you all you need to know, Knowing what a good flare looks like will allow you to inspect the flares you make in the "good" lines as well as your test lines.
First pick up a section of pre flared line at your local parts house to use as a benchmark of an ideal flare. I'd suggest using the available preflared lines anyplace you can get the right length for safety and ease.
Now practice making flares. Make sure you cut off a couple inches past the test flare each time to remove any work hardened section.
Tip #1: DON'T cut the tubing with a tubing cutter! The standard cutter will compress the end of the tubing, work hardens it and leaves a tapered cut. The likelyhood of a good flare is highly diminished already! Use a thin cutoff wheel in a dremel type tool to cut the tube. Flatten and square the end with a fine toothed swiss pattern file. If your flaring tool is the standard type that clamps the tube between two block, snugly clamp the end of the tube even with the top of the blocks and use the blocks as a guide to file the end square. Use a 3 corner scraper or slender knife blade to remove all burs from inside the tube and a twist or two of the corner against a sharpening stone to remove any outside burs. DON'T wrap a piece of sndpaper around the end of the tube and twist like you are cleaning a copper water pipe for soldering! You don't want any circumferal scratches around the end of the tube! Get the idea yet that preparation of the tube is key to a good flare??? IT IS!
Make your flare according to the directions for your tool. do not over tighten the tool, you just want to make the bends, not crush them.
Examine the flare you made and compare to the sample (under magnification is best, an Optivisor with a #3 or 4 plate is a well spent 20.00!). The flare should be round, especially the inner end of the double flare, concentric, not distorted, and square to the tubing. The outermost bend should be slightly rounded not completely crushed, sharpcornered, or show any tool marks. There should not be any circumferal tool marks on the neck of the tubing just below the flare either. Any tool marks or scratches, even fine ones is the start of a crack waiting to happen.

 

Quite a symposium on making flares! Thanks, that is very helpful.

Gustave

 

No problem! When installing brake lines on a drag car, the last thing you want is for a flare to blow out at 150+ MPH, so I learned to be very fussy. The new hydraulic flare tools are the real answer today, but all that was available back in the day were the basic manual ones so we learned to use them the best way possible.

 

What, no parachute?

 

Not in the classes we raced.

 

Also excellent advice. Thanks.

I'd like to test a few home-brew connections, just to see what happens. Though AX's advice would also be used, to develop a correlation between what looks like a good flare, and what works in practice.

It is interesting that the common SAE 45 deg double flare apears to be more of a one-use type of system. From what I've read the performance is degraded on multi-use, as it relies in part on crushing the flare to achieve a good seal. AN-3 does appears to be better for multi-use.

Dr G

 

Gustave,

Check out this website Federal Hill Trading Co.

This tubing bends real easy is fairly cheap and they will rent you the flaring tool for $25/- week

I will be installing some brake lines in the next couple of weeks and will let you know how it goes if you are interested

Chris

 

This is the Rolls Royce of flaring tools if you are in the market and appreciate fine tools:
Amazon.com: MasterCool Universal Hydraulic Flaring Tool Set: Automotive

 

AXracer, has given you the best step by step method of preping and flaring brake or oil lines. I would suggest that if your intendition is to use stainless steel that you use seamless tubing. Here are a couple of sources I used to fab brake and oil lines for my Bobber and my truck.
http://www.bikernet.com/garage/PageV...asp?PageID=328
http://www.rx7.org/Robinette/flare_brake_line.htm

 

You know, I just ordered some of this stuff last night to play around with.

Gustave

 

I was eyeballing that baby. It's not cheap, but I am a tool junky and consider them an investment. If you take care of them they can always be sold when you think you won't need them ever again. Of course every time I've done that with a tool, I've needed it a few months later on.

But with Tilton master cylinders and Wilwood calipers, I don't think there will be any 45 deg double flares in my system. So a good 27 deg single flare tool is probably what I need. I could use that for fluid-cooler hard lines also.

Gustave

 

I mispoke. The AN fittings are 37 degree flare, not 27 degrees.

It did not occur to me until today that you don't need to use SAE 45 deg double flare connections, except maybe at the master cylinder if it requires them. This is still a work in progress, but the advice given here will be very usefull for any hard line project.

Thanks folks.

Gustave

 

Thanks for posting the question Dr G. I am always amazed at the depth of knowledge on this forum. I will be replacing the brake lines on my '52 F1 soon and I learned a lot here.

Thanks

Steve