Re: [ihc] Flaring tool?

["Ryan Moore" <baradium@xxxxxxxxxxx>]

----- Original Message ----- 
From: "Richard Welty" <rwelty@domain.elided>
To: <ihc@domain.elided>
Sent: Thursday, February 26, 2004 13:07
Subject: Re: [ihc] Flaring tool?


> On Thu, 26 Feb 2004 11:48:51 -0700 Joel M Brodsky <jmbrodsky@domain.elided>
wrote:
>
> > I have two flaring tools.  Use them often.
> > I'm curious about what it means to 'double flare' something.
> > Does that mean that there is a layer of material folded over the first
one
> > so that the flared section is actually
> > a sandwich of two layers of material?
> > OR
> > Is a double flare just like a bulge in the line, like a flare-out
followed
> > closely by a flare-in - like on a factory fuel pump outlet pipe for
> > mechanical fuel pumps on '70s SVs?
>
> both.
>
> in the SAE system (US cars, english thread), double flaring is
> the former.
>
> in the Metric system, ISO flares are "bubble" flares, which are the
> second thing you described.
>
> richard

What he said...

Also, just FYI, aircraft use a different pitch to the flare than automotive
applications do.  An automotive flare is 45* while a flare for an aviation
application is 30*.  The idea is to prevent automotive fittings from being
usable on aircraft (if you use the aviation flare equipement it won't fit).
However, you *can* use the aviation fittings on an automotive applications,
but it won't seal quite quite as well (only at certain points, although most
likely, with most peoples' flare ability, it probobly won't many
difference).

The double flare in SAE means that as the flare is made you do fold the end
inside of the flare, this prevents a rough edge from being present in the
flare and presents a better sealing surface.  Note that the automotive
fittings have a 45* pitch to match what the pitch of the flare *should* be
if done correctly to provide a much greater sealing area.  There are other
methods of connecting areas of hard lines together, but they are generally
best left to people who know how to use the parts and tools.  This is why
compression fittings are generally though of as unsafe in automotive
applications, when done correctly they are still safe, but most people don't
know how do do them correctly.  This is why those fittings can still be used
in critical high pressure hydraulic situations in aircraft, the mechanics
have the knowledge to ensure the connections are done correctly.  FWIW, a
standard double flare is still the preferred method when connecting two hard
lines.  There is also a soft aluminum "washer" tyle part that can be
obtained for flares.  If you have a leaky or damaged flare (either at the
fitting or the flare itself) you put that in there and it will fill in the
gaps when tightened.  This allows aircraft mechanics to save on replacing
high cost parts without compromising safety.

I'm sure many of you are aware of the different styles of fittings.   Please
note that AN and AC fittings are *not* interchangable.  You'll get them to
start to fit, and they'll tighten, but you will not have an appropriate
seal.  This is due to the "shoulder" present on the AN fittings which is
absent on the AC fittings (the AC fittings start their taper immediately
after the end of the threads).

Hey, looks like I'm learning *something* from my systems class at least.
BTW, the aviation flare tools make that automotive snap-on one look cheap
and primative.

-Ryan


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