The tube is gripped between the halves of the die
block with the end of the tube projecting slightly above the bevel of
the die block hole.
Then, the first-step die plunger is placed
against the tube with the end of the tubing resting in the plunger
recess. The plunger is then forced toward the die block, causing a
bead-like swelling at the end of the tubing. The first-step plunger
is then removed, leaving the tube in the die block.
Second Step. The cone is placed at the beaded end of the tubing.
This plunger is then forced against the bead, causing the metal at
the upper half of the bead to fold into the lower half. This forms a
flare with a double thickness of metal at the lip.
Lack of care and attention to detail in forming flares is likely to
result in producing a faulty flare.
If the tubing is not cut
squarely, a lopsided flare results. A faulty flare is also produced
if the tube is not inserted far enough into the die block resulting
in an underflared condition.
An underflared tube has a small
gripping area and will pull apart under pressure.
If the tube is
inserted until it protrudes too far past the edge of the die block,
an overflared condition results.
This can cause the flare to crack
or break. Use of the stop will prevent this type of overflare. Too
much force used on the forming tool when making a flare results in a
cracked or flushed flare.
After the tubing has been formed and flared, all oil, grease, and
other foreign material must be removed before installation. Removal
of every trace of oil and grease from oxygen tubing is a matter of
critical importance because contact between bottled oxygen (used for
breathing) and oil or grease results in spontaneous combustion and
Fittings are used to assemble and interconnect tubes and hoses to
plumbing components and for connecting lines through bulkheads.
Examples of these fittings are shown in Figure 2-11.
Prior to installation, all fittings must be carefully examined to
ensure that their surfaces are smooth.
Smoothness consists of
freedom from burrs, nicks, scratches, and tool marks.