M E C H A N I C A L LY O P E R AT E D T U B E
BENDER.--The tube bender, shown in figure 10-35,
is issued as a kit. The kit contains the equipment
necessary for bending tubing from 1/4 inch to 3/4 inch
in diameter. This tube bender is designed for use with
aircraft grade, high-strength, stainless-steel tubing, as
well as all other metal tubing. It is designed to be
fastened to a bench or tripod, and the base is formed to
provide a secure grip in a vise.
The simple hand bender shown in figure 10-34 uses
two handles as levers to provide the mechanical
Figure 10-35.--Mechanically operated tube bender.
advantage necessary to bend the tubing, while the
cut, cleanliness, and no draw marks or scratches. Draw
mechanically operated tube bender employs a hand
marks can spread and split the tube when it is flared.
crank and gears. The forming die is keyed to the drive
Use a deburring tool to remove burrs from the inside
gear and secured by a screw (fig. 10-35).
and outside of the tubing. Remove filings, chips, and
The forming die on the mechanical tube bender is
grit from inside the tube. Clean the tube. Slip the fitting
calibrated in degrees similar to the radius block of the
nut and sleeve onto the tube. Place the tube into the
hand-type bender. A length of replacement tubing may
proper size hole in the grip die. Make sure the end of the
be bent to a specified number of degrees or it may be
tube extends 1/64 inch above the surface of the grip die.
bent to duplicate the bend in the damaged tube or
Center the plunger over the end of the tube and tighten
pattern. Duplicating the bend of a damaged tube or
the yoke setscrew to secure the tube in the grip die and
pattern is accomplished by laying the pattern on top of
hold the yoke in place. Strike the top of the plunger
the tube being bent and slowly bending the new tube to
several light blows with a hammer or mallet, turning the
the required bend.
plunger a half turn after each blow. Loosen the setscrew
and remove the tube from the grip die. Check to make
NOTE: Certain types of tubing are more elastic
sure that no cracks are evident and that the flared end of
than others. It may be necessary to bend the tube past
the tube is no larger than the largest diameter of the
the required bend to allow for springback.
sleeve being used.
Before bending aluminum alloy tubing, it should
The double-flare tube joint is used on all 5052
be packed with fusible alloy Federal Specification
aluminum alloy tubes with less than 1/2-inch outside
QQ-F-838. In an emergency, when aluminum alloy
diameter, except when used with NAS 590 series tube
QQ-F-838 is not available, aluminum alloy tubing may
fittings and NAS 591 connectors or NAS 593
be packed with shot or sand and both ends closed with
connectors. Aluminum alloy tubing used in
protective closures before bending. Where sand or
low-pressure oxygen systems or corrosion-resistant
fusible alloy is used, wash or blow out all particles after
steel used in brake systems must be double flared.
the tubing has been bent. Particles of aluminum alloy or
Double flare reduces the chance of cutting the flare by
sand can cause serious damage to component parts.
overtightening. When fabricating oxygen lines, make
Tube Joint Preparation
The two major tube joints are the flared fittings and
flareless fittings. Preparations for these tube joints
FLARED FITTINGS.--There are two types of
flared tubing joints--the single-flared joint and the
double-flared joint. The single-flared tube joint is used
on all sizes of steel tubing and 5052 aluminum alloy
tubing that conforms to Federal Specification
WW-T-700/6 with 1/2 inch or larger outside diameter.
Use the tube flaring tool (fig. 10-36) to prepare tube
ends for flaring. Check tube ends for roundness, square
Figure 10-36.--Tube flaring tool (single-flare).