I endorse what TonyK said about using a tube cutter.
AC43.13-1B gives the tightening torques for AN-818 nuts on alloy tubing as
50 to 65 pound inches for the -4 size (1/4" tube) and
110 to 130 pound inches for the -6 size (3/8" tube) .
Not having a low-range torque wrench I resorted to a spring balance pulling on
the free end of the spanner. The figures for -6, at least, turned out to be a
firm but not hard pull on the length of spanner normally encountered for this
size of hexagon.
Sealing compound is not needed, though make sure the flare is clean and
burr-free both inside and outside and the fittings are clean.
The only tip I would pass on (except for remembering to slide the nut and sleeve
onto the tube before you make the flare ..... :-) ) is, as it says on the
tool, to clean and oil the flaring roller every time before you use it. Then
the roller will slide over the tube without picking up. The oil gets
everywhere, but that is better than a scuffed flare.
John Cliff
#0259
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