17 replies to this topic

[mbolt998]

 

So now I'm really confused again :) It looks from that post about the flare types that if I do the first operation with my tool, that's actually a "double flare". If it then turn the tool around and do the second operation, I have an "inverted" flare. Is this right?

 

Correct.

Those are the Terms used by the SAE and the only ones I use.

I have seen in particular the 'double flare' term interchanged with an invert flare may times - as per Bobbin's post above (and note that is not from the standards) - and as you can see, from the SAE and BMC Standards, they are very different things.

Most tooling works as you have said, first operation is to make a Double Flare then if it's needed, from the Double Flare, form an Invert Flare. I have a few tools for making them, they all work this way.
 

 

Thank you for clearing this up! I will try to remember. The confusion arises I think because you do two operations with the tool to get the inverted flare, and that feels like "double" of something, and like if you only did the first bit you would have a "single" flare.

 

I used inverted flares everywhere on my car, including both sides of an inline junction, which probably should have been double into inverted. But it's not leaking.

[stuart bowes]

so just to round out the post and make sure I do actually understand (always worth a double check and others might find it useful)

 

if the fitting you're connecting to has a convex ('outy') mating surface then you want one of these

 

 

and if the fitting you're connecting to has a concave ('inny') mating surface then you want one of these

 

 

and once you've done them up nice and tight they not only give a good seal, but also the shape of the fixings holds that flare in place and prevents it being deformed again, i.e. will not break free or pop out 

 

pretty obvious really once you know, my mistake was not paying attention closely enough to realise there were a mixture of the two types on the car that's all

 

and then the thread sizes are as per Spiders very useful post above marked in green (again, recognise there are are different types mixed up around the car)

 

im not a huge fan of the way the tool grips the pipe and marks it, but it is superficial as far as I can tell, the fixing covers it up anyway so im not losing sleep over it

 

I've opted for long male fittings and short female fittings, that way as it tightens you can see some 'spare' thread left and you know you've hit the bottom of the connection and pulled it in tight, as opposed to running out of thread and not being sure if that's why it wont turn any further

Edited by stuart bowes, 07 June 2025 - 12:09 PM.

[weef]

Essentially what is happening when you use the "inverted flare"  is that when tightening you are using the tube nut to deform the flare to make the seal, basicly replicating the second flaring tool  operation.

 This practice make well work on the soft copper tubing but may not be so successful if the tubing is steel or the more common cupro nickel tubing used in brake line renewal.

Now you understand the flaring principal, please flare the correct profile for the job in hand.