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What is the difference between single and double flare line? Do brake lines require double flare line connections? What about fuel lines? I have a regular (single) flaring tool, is there a different tool for double flares?

TIA
 

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What is the difference between single and double flare line? Do brake lines require double flare line connections? What about fuel lines? I have a regular (single) flaring tool, is there a different tool for double flares?

TIA
I am not an expert, but someone will correct my errors I am sure:

1. double flares round the inside of the tube to provide a better seal than single flare. You have to use an additional mandrel-type thing (dont know the 'proper' name offhand) to produce the double flare after the single flare is done. These mandrels usually come in the flaring kits.

2. Brake lines will leak if you do not double flare. Fuel lines are OK with a single flare IIRC, if you mean carbuerator line (NOT fuel injection).

3. see #1.

here is a good link on flaring steel tube, it shows the 2xflare mandrel I am talking about:

http://www.joesfalcon.com/gentip2/gentip2.html
 

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IME, a double flare lasts longer and seals better under the kinds conditions automotive brake systems operate under (vibration, hot-cold cycling and pressure). By folding the tube end over and under while stretching it out as the flare is made, strength is added to the flare to mitigate the tendancy for the stretched material to work harden and crack over time, causing leaks. Part of this is due to the small, thin tubing used. I make single flares in large diamater hydraulic tubing all the time and they operate fine in the 1.5-3 Kpsi range my systems utilize.

Get the double flare mandrels and use your single flare tool. I haven't noted any difference in the outer flaring device in the tools I've used. I often have had to make the double flare insert (which goes into the tube end when the flare is begun to start the fold-over) because the ones commercially sold aren't strong enough to fold over the SS tubing I use (even though it's normalized). Double-flaring can be a tedious process so take your time and buy an extra mandrel in the size you use most (3/16" for me).

Lastly, make sure you buy annealed steel tubing designed for brake and/or hydraulic applications. It'll make your life and flaring so much easier..*G*

Have fun!
 

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I know most (if not all) brake lines come double flared from the vendor. Our long line (from front to rear) was bent in half (a nice gentle bend, mind you) and it was very easy to unbend by hand. So far I've installed about half of our new stainless steel brake lines and most have had to be "adjusted" manually. <interpret that as "bend them by hand until they fit"> As for fuel lines, I think they come single flared, but I haven't messed with ours and don't plan to. As for the tools required, I have no idea.

TK
PS - If you need pictures of the brake lines, check out my sig area.
 

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Oh, forgot....most fuel line can be single-flared, although I did double flare the aluminum tubing on the race car fuel system because of vibration and I had noticed some flare edge cracking in the 3003 tubing I used when using single flares.
 

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Invest in a double flare tool kit. You can get one from any major tool place.I happen to have the Snap-On/ Blue Point kit. Brake lines are nothing to skimp on. Besides, it's kinda fun.
 

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I am so glad you responded to this post Pat. I was wondering (or wandering(in the mind) as my kids would say) about this very same idea of using the single tool for the double flare . My dbl flare tool is a cheapo, but the single we have at work is a really great tool. Thanks for the info, as I will give this a try. ::
 

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Just so I'm clear, the anvil on a single flaring tool does the work the same for finishing a double flare but one needs the starting mandrel to begin the fold-over process on the end of the tube. If one doesn't have that, no double flare is possible.
 

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Prior to clmping onto the tube, be sure to bevel the outside edge of the tube. That'll make the bending over much, much easier.
 
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