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What's the secret to double flaring brake lines?

Discussion in 'The Hokey Ass Message Board' started by Gigantor, Dec 12, 2007.

  1. Gigantor
    Joined: Jul 12, 2006
    Posts: 3,823


    All right ... I give up. I bought a flare tool to double flare my own hard brake lines. It cost me about 40 bucks, so I don't think it's a total piece of crap, but damned if I can get a decent flare ... they end up all off center and lumpy, and I KNOW it will leak. I've ruined two brake lines trying to master it. So, what am I doing wrong?
    I cut the lines with a pipe cutter, then debur them with a drill bit and a fine file ... but when I crank down on the die, it somehow gets off centered and doesn't make an even crown.
    Is there a trick? I lost the instructions which specify how much pipe should be sticking through the hole, but I experimented with various lengths and STILL haven't been able to get it right.
    Someone please enlighten me.:confused:
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 54,493


    not all double flare tools are created equal, unfortunately.

    I use a 45 degree deburring bit on the inside and a file on the outside, to try to get a nice 45 degree chamfer inside and out. Sometimes it works, some times it doesn't.

    I also usually leave some extra line so I can have a few tries to make the flare work, if it screws up I cut off as little as possible and try again.

    Maybe someone will link to a fail-safe brand of double flare tool, my guess is it would be spendy, but probably worth the money.
  3. Deuce Roadster
    Joined: Sep 8, 2002
    Posts: 9,519

    Deuce Roadster
    Member Emeritus


    Most tools have a little button that you use a gauge ... and that is the amount you leave sticking out ...

    I quit the hand tool flaring tools ... and went with the hydraulic ones ... SUPER flares every time ... :) but not inexpensive ... about $300.00 :(

  4. First, make sure the top of your line is perpendicular to your adapter.If it isn't, it will go off to the side like you are doing. Next "most" adapters the brake line will stick out to either to top of the main surface of the die or if there is a "step" to the step. If it is out too much, it will also try that. Also try a small drop of oil on both sides of the die. If that doesn't work, hit me up again.

  5. Sam F.
    Joined: Mar 28, 2002
    Posts: 4,225

    Sam F.

    a double flare is exactly that ,,a DOUBLE flare,,first stick the brake line through the aluminum holder,,take the die(upside down) and measure how much the line needs to stick throught the aluminum holder holding it side by side to the line,,then flip the die over stick the die into the line and the clamp the press down into it,,,THEN take the die out, ,,,and re-CLAMP it AGIAN!

    a double flare!
  6. squirrel
    Joined: Sep 23, 2004
    Posts: 54,493


    you know, he didn't mention using the little button to make the bubble first.

  7. RugBlaster
    Joined: Nov 12, 2006
    Posts: 563


    as stated, use some type of oil on the flare......this will should do more towards a favorable outcome as anything. chamfer the end of the tubing, the screw in gently.....not to tight.
  8. chaddilac
    Joined: Mar 21, 2006
    Posts: 14,016


    I use this one as well.... took me a little bit to get used to it. You're supposed to push the line through the thickness of the small black flare piece. I ended up shortening that about 1/16" of an inch and you'll have to keep an eye on it when it starts to push to one side and keep the tool straight. It's kind of tough but keep trying you'll get it...

  9. Zombie Hot Rod
    Joined: Oct 22, 2006
    Posts: 2,453

    Zombie Hot Rod
    from New York

    I've used the cheap flaring tools for years, threw more of them across he garage than any other tool I own. I went out and spent the extra money on a the hydraulic flaring tool and it was worth every nickle spent. Perfect flares the first time. Rarely do I have to go back and re-flare something when I'm bleeding the brakes for the first time. If you build alot of cars or do alot of brakes I sugguest getting one, you will not be disappointed.

    I noticed with the older hand tools it helps to not only deburr the inside of the tubing but to put a small bevel on the outside edge. You can just spin it around once on a belt sander, it will make flaring the lines alot easier and they will come out straighter the first time.

    Also helps to clamp the end in a bench vise.
  10. slddnmatt
    Joined: Mar 30, 2006
    Posts: 3,683


    i always use some brake fluid or some kind of lubricant to flare, it helps alot but there are usually a couple that still i have to redo. might have to look into that bling--bling hydraulic one!
  11. Deuce Roadster
    Joined: Sep 8, 2002
    Posts: 9,519

    Deuce Roadster
    Member Emeritus

  12. leon renaud
    Joined: Nov 12, 2005
    Posts: 1,937

    leon renaud
    from N.E. Ct.

    another note on flaring your own lines i learned the hartd way .I have a Snap on Tools flaring kit from my commercial mechanic days.I bought brake line from Advanced auto motive and couldn't get any type of good flare in some cases the line would push right through the holder ,OK the tools are old might need replacing bought another name brand flaring kit and got same results as with Snap on !I went to NAPA and bought a roll of line from them and like magic both kits worked fine! apparrently the "ese" Chinese japanese what ever ESE line is crap !and a lot of the ready made ;lines are this stuff.
  13. solo_909
    Joined: Apr 9, 2006
    Posts: 1,786


    heres the secret dont do it! lol its a pain in the ass itself to bend the things just right why take the chance of messing up the double flares. Take it to a shop and have them do it. Its cheap and perfect.
  14. lewislynn
    Joined: Apr 29, 2006
    Posts: 2,106


    That reminds me, a few yrs ago I took my F250 to a national name shop to replace the rear wheel bearing. I always like to pop in on mechanics...err I mean, technicians on the rare occasion I have shop work done. When I walked up to my truck I noticed the "technician" was using a pair of Vise Grips to pinch the (rubber) brake line to the wheel so he wouldn't have to bleed the brakes...I went to the desk and told them to replace the hose on that wheel and bleed the brakes at their cost or I was turning them in to the state.

    Anyway, it's those kinds of reasons I rarely have shops do my work.

    I won't say who it was but I will say it wasn't Sears.
    40 Coupe Since 69 likes this.
  15. lewislynn
    Joined: Apr 29, 2006
    Posts: 2,106


    I bought one from Pep Boys for $16.00 (assuming everyone's heard of Pep Boys). They were a little crooked but it worked great on my 5/16 fuel lines, I don't know about the pressure from a brake line. ...I do know just about any brass fitting or pipe nipple made in China will leak.
  16. skajaquada
    Joined: Sep 14, 2004
    Posts: 1,642

    from SLC Utard

    wow...i can't believe someone could be working at a place like that and be that stupid. our power bleeder takes like 5 min total to do an entire system, and that's if you're a moron. fucking lazy assholes. of course that's why our shop gets so much business, we like to do things right :p
  17. lewislynn
    Joined: Apr 29, 2006
    Posts: 2,106


    I'll just say as near as I could tell , by the blank stare without comment of the "technician"at my reaction, it's directly related to the illegal immigration problem....Maybe it's a cultural thing.
  18. montclaire
    Joined: Jul 24, 2007
    Posts: 501


    Try heating the line before you flare it, this will keep the line from cracking.
  19. I have an old Blue Point double flaring setup. I twist a countersink bit in the opening of the tube by hand to clean up the ID and a fine tooth file on the outside to chamfer the outside. Don't chamfer it too much or you might wind up with a crooked end. You stick the tube through the clamp jaws of the tool and hold the adapter piece along side it flat against the side of the tube. The side of the adapter is the thickness that the tube is supposed to protrude through the hole. Then clamp the tube tight in the jaws and stick the adapter nub into the tube. When you first guide the cone of the flaring tool into the adapter, and the slack is almost taken up before doing any actual squishing, rotate the U shaped piece back and forth a little as you start to snug it up, and watch that the adapter is sitting parallel to the face as you start cranking in for real. There's a little bit of side to side slop in there, but if you sort of inch up on it while jiggling it and watching it close and keeping it straight, you can keep the little adapter thing square and parallel. Then crank away. Use a vice to hold the jaw part of the tool so you can use two hands -- one hand keeping the adapter nub piece centered and square, and the other hand to crank in slowly and adjust the U-shaped piece so that it holds the adapter straight. If it's straight when you start cranking, it'll stay straight all the way down.

    I never made a bad flare with that Blue Point flaring set. I did make some bad flares with another set that was some cheap import copy that looked almost identical. The main problem I had with the cheap import set was that the serrated jaw part that's supposed to grip the tube wouldn't get a good grip no matter how tight it was, and the tube would partially slide back down instead of forming a good bulb shape.

    I put a little dab of white lithium grease on the adapter nub and on the cone of the flaring tool, and that seems to help make nicer flares.

    If the little nub in the center of the adapter piece is bent, then it might be hopeless and you'll need to buy a new adapter piece.

    Good luck!
  20. spoons
    Joined: Jan 1, 2004
    Posts: 1,738

    from ohio

    When you want to make your own lines, DON"T buy $16.00 tools. I have a Rigid hand held unit that I have been using for 10 years. Costs about $100.00 and works every time. Has instructions and everything you need in it. Big thing is to Practice on some scrap stuff you might have laying around..
    Cut the tube with tubing cutter (straight and square), chamfer ID, deburr od a little, follow instructions ( can find how-to tips on Google ). A little oil helps as well...
    I'm no expert, but taking your time is a big thing here....
  21. headhunter
    Joined: Oct 5, 2005
    Posts: 271

    from Austin, TX

    I used the same cheap Pep Boys tool you're probably talking about and had the same problem over and over again - then I took apart the block and looked at the holes that hold the line when you clamp down to do the flaring.... every single one of them was at an angle - you could SEE it. Ah ha! That's why every flare I did was lumping over onto one side! I went back to the store and opened packages and checked the blocks on a few until I found one that was straight. Once I fixed that, it worked like a charm, no need for $100 tools.
  22. Gigantor
    Joined: Jul 12, 2006
    Posts: 3,823


    Wow- All kinds of ideas, tips, advice, experiences ... Thanks. I might have to spring for the nice tool ... just not right before Christmas, if you know what I mean ;)
    Here's the deal as far as I can see:
    1) I need to check the tool itself to make sure the clamp is straight.
    2) I need to lubricate it.
    3) I need to put the clamp in a bench vise.
    4) I need to stop buying the shitty-shit from advanced auto and get good stuff at NAPA.
    I read online last night that the brake lines with the seam that come from places like Advanced, Pep Boys, etc, can't handle the double flaring technique very well.
    And yes, I do know what Double Flaring means ... of course I'm using the button first!
    Thanks again guys...
  23. pasadenahotrod
    Joined: Feb 13, 2007
    Posts: 11,776

    from Texas

    The SECRET is like a lot of other things(welding, cutting, cunnilingus, painting) ... PRACTICE, PRACTICE, PRACTICE.
    It's no big deal to sacrifice an hour or two and a 3 or 4 or 6 foot stick of brake pipe to LEARN how to use a double-flaring tool correctly.
  24. tommy
    Joined: Mar 3, 2001
    Posts: 14,757

    Member Emeritus

    I always clamp the long ear of the tool in the vise. My tool says to lay the button upside down on the tool using the ridge on the side of the button as a gauge for how far the tubing protrudes above the surface of the tool. Push the tubing through the tool until it's even with the ridge on the button and clamp it down. I use channel locks to tighten the wing nuts so that the tubing won't slip out. I've never really had any problems. I can see if you have too much tubing above the surface that the tubing may want to deform before or as the bubble is formed. The only real critical area is the face of the flare itself. This is where the seal takes place.
  25. captainflight
    Joined: Jul 7, 2007
    Posts: 198


    Lots of auto parts shops sell pre-made brake lines with fittings in a wide variety of lengths. If you are not making lines too often, it may be something to consider.
  26. Gigantor
    Joined: Jul 12, 2006
    Posts: 3,823


    Pasadena - as you said, some things are more fun to practice than others ... I need to master this, I've only ever gotten one good flare out of that tool, can't figure out why it's giving me problems now ... right now I just need to get it done - it's too frikkin cold to fiddle around outside at the moment.

    Captain Flight - No luck at all finding a brake line with the two different fittings I need... believe me, I tried.
  27. carlos
    Joined: May 2, 2005
    Posts: 1,387

    from ohio

    deburr inside,chamfer just a bit on outside,correct measurement,get the first step started and finish with second.if they are off center you are not geting the burr offthe inside and it is cocking the die
  28. gashog
    Joined: Dec 9, 2005
    Posts: 984


    The only time I get bad flares is when I don't evenly tighten the wing nuts on the tubing holder. It doesn't take much to it throw off the tube center or the flaring mandrel. If I forget and tighten the one end more than the other, I get a bad flare every time. It is important to use lubricant and to set the correct amount of tubing to be flared with the gage supplied with your kit, but my $10 Taiwan Snapon kit works great.
  29. Hot Rod To Hell
    Joined: Aug 19, 2003
    Posts: 3,036

    Hot Rod To Hell
    from Flint MI

    I will reiterate the praise of the hydraulic flaring tool.

    It's made by a company called "Mastercool"; I got the "Universal hydraulic flaring tool set", which cost me about $225 on Egay, brand spankin'.

    This will do single and double flares in 45*, metric bubble flares, and GM "Push connect" flares. I believe that there are dies available to do other flares as well (I'd like to get a set for 37*AN flares).

    While this was spendy, I honestly believe that I have spent this much on all of the "normal" style of flaring tools I've purchased trying to find one that works. I've tried everything from the $5 swap meet tool, to the Rigid, to the Snap on, and they are ALL junk.

    I've only made about 15 flares with this tool so far, but EVERY one has been PERFECT on the first try. With the very first flare I made on a piece of scrap line, as a test, I actually said to myself "Wow... I can't believe I've been working on cars this long without this tool.".

    Buy it; you won't regret it.
  30. Andy
    Joined: Nov 17, 2002
    Posts: 5,063


    The problem is most probably the button that is used to bubble the end of the line. Name brand is no guarantee. I had an Imperial Eastman button that was not machined correctly and the flares were terrible. I bought a new button from NAPA and looked at it closely. It was fine and I never had another problem. Compair all of your buttons. Especially the shape next to the post.

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