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Preparing AN Hard Line
To properly plumb a hydraulic system, be it fuel, coolant
or lubricants, you need to be prepared to use a combination
of hard line and soft line. Hard line offers rigidity, durability,
and prevents pressure loss associated with rubber or braided
line. Here is how to correctly flare aluminum or steel line
and select the proper AN compression fittings.
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Making a good flare that will not leak begins with a straight
and clean cut. We prefer using a tubing cutter such as
this Craftsman style. Be sure to have a fresh cutting
wheel in the tool, especially if cutting on steel line.
Clean up the burrs and edge left by the cutter using a
drill bit of the same size as the inner diameter of the
tube. A 1/2-inch aluminum tube is shown here 
AN flares require a special 37° flaring tool (see
side bar.) Place the tubing in the flaring tool clamp.
Allow 3/8-inch of tube to protrude above the tool. 
Spray a little WD40 or oil on the cone prior to creating
the flare. Turn the handle smoothly and ensure the cone
enters the tube straight-on, other wise you'll get a crooked
flare that will likely leak.
Shown is a perfect 37° AN flare. The circumference
of the flare is symmetrical and there are no blemishes
that could cause leaks against the male AN fitting.
Remove the tube clamp and use some light sand paper to
smooth off any marks left by the clamp.
Finally, slide up the compression sleeve, it should mate
squarely with the back of the flare. 
Flare
Angles
