MODEL 3 TUBE BENDER
Assembly & Operating Instructions
- Die Set Components
- A Die Set refers to the components
that are used in the bender to hold the tubing or pipe during the
bending operation. This
- section does not describe the
operation of the bender. This section's purpose is to simply
familiarize you with the different
- components that make up a 'Die
Set'. Knowing how the different die set parts interact with each
other is essential in operating
- the bender correctly. The die set
must match the size of the tubing or pipe being bent. For example,
never bend 1 1/2" tubing in
- a 1 5/8" die set. This may
damage the followbar's inserts.
- First, let's explain the difference
between tubing and pipe. Tubing is specified by its outside diameter
and a wall thickness.
- For example, 1 1/2" x
.095" tubing has an outside diameter of 1 1/2" and a wall
thickness of .095". On the other hand, pipe is
- specified loosely on its inside
diameter. We say loosely because the pipe's size may not actually be
its inside diameter. Confused
- yet? Just remember pipe is commonly
used for the purpose of transporting fluids. Fluid flow is only
concerned with the inside
- area of the pipe and the outside
makes no difference what so ever. Pipe wall thickness is specified
as a schedule number and
- is obtained from a pipe chart.
Another example, 1 1/2" schedule 40 pipe has an outside
diameter of 1.900" (larger than 1 7/8")
- and a wall thickness of .145"
and an inside diameter of 1.610" (near 1 5/8"). So, when
ordering die sets be careful to specify whether
- it's a tube or pipe size die set.
- ROUND GROOVE DIES:
- A Round groove die set consists of
three main elements:
- 1) Forming Die
- This is the part that the tube or
pipe actually bends around. It has a circular groove machined around
- Please note that this groove is
machined with a specially designed profile to help in reducing
flattening of the bend's outside.
- If you lay a section of tubing into
the forming die you will notice that it will NOT completely seat
into the die's groove. This is
- normal for tube size dies and
becomes very important as the tube's wall thickness gets thinner.
However, forming dies that
- are machined for 'Pipe' instead of
tubing are generally not manufactured with this profile and the pipe
may completely seat
- in the groove. Pipe is much more
forgiving when it comes to bending it because of its thicker wall.
Stamped into the top is
- the Outside diameter of the tube or
pipe and the centerline radius (CLR) of the forming die. Above is
pictured a 3/4" die with
- a 2 1/4" CLR and a 1 1/2"
die with a 4 1/2" CLR.
- Drive holes are drilled into most
dies with a radius of 3" or larger. When the 7/8" drive
pin is inserted into the drive links,
- it will pass through these holes.
This is how the drive links rotate the forming die. The 1"
drive holes are drilled oversize to
- permit easy insertion of the
7/8" drive pin.
- Die sets with a radius smaller than
3" will generally not have drive holes because there is no room
to drill them. As
- explained in the following section
on how to operate the bender, the diameter of the tubing or pipe is
so small the bender
- can be operated without the use of
the ratchet mechanism.
- U-straps are sized to the OD of the
pipe or tubing being bent. The
- size is stamped onto them.
- 3) Followbar (Also referred to as
the Pressure Die)
- The Followbar is the component that
presses the tubing into the forming die to create the bend. Shown in
the illustration below, it
consists of three main parts: a backing block, an angled rear insert
and a straight 0 degree front insert. This multipart design
allows the inserts, if damaged or worn out, to be inexpensively
replaced without having to purchase a whole followbar assembly.
The Inserts are permanent cast from a special bearing grade
anti-galling material to protect the tubing from scratching
during the bending process and then CNC machined to size. They are
silverish in color but are NOT aluminum.
- REPLACING INSERTS
- The placement of the inserts into
the backing block
- must be done properly or poor
quality bends will result.
- Notice one insert is marked 0
degrees. The other insert
- will be marked with the angle that
is appropriate for the
- radius of the forming die (usually
3 or 5 degrees). The
- angle in the rear insert helps to
support the tube or pipe
- after the point of bend, greatly
reducing flattening. When
- bending, the angled insert will
always be closer to the
- forming die, and the U-strap for
that matter, than the 0
- degree insert. Notice in the figure
to the right, that the tall
- side of the angled insert must face
the U-strap side of the
- The front 0 degree insert has a
- into one side of its groove. This
chamfer must face away
- from the rear insert, thus allowing
the tube or pipe to slide
- through easier.
- To replace the inserts, simply lay
the Backing Block
- flat with the engraving facing up.
The Backing Block may
- or may not be as thick as the
inserts. If it is thinner, place
- spacers under the Backing Block so
that when the inserts are inserted they are centered in the
dovetails. This is important.
- Now tighten the 1/2" locking
bolts and you're done.
- COMPLETE ROUND GROOVE DIE SET
- Above is pictured all of the
components which make up a complete die set for round tubing or
pipe. In the figure to right,
- you can see two red lines drawn at
90 degrees apart. These lines are marked as 1 and 2. Line 1 runs
from the center of
- the forming die's center hole to
approximately the middle of the angled rear insert. Line 2 runs from
that point parallel to the
- tubing. This illustrates the basic
principle of how the components relate to each other. It is vital
that when bending the rear
- insert is positioned as shown. For
example, suppose the followbar in engraved with hole 6 as shown, but
you install it in
- hole 7. The rear insert will be
shifted to the right of line 1 and the angle machined into it will
have no effect during bending.
- This will generally cause
flattening of the tubing's outer side and may also cause wrinkling.
If you experience this problem
- and you have the followbar
installed in the correct hole, the rear insert's bending position
can be easily checked. Simply place
- a short piece of tubing into the
bender as if your were actually going to bent it. Apply enough
bending force to remove any
- play but not actually bend the
tubing. Now hold a 90 degree carpenter's square above the bender so
that its outside edges
- are positioned similar to the red
lines shown. The center of the angled rear insert should be roughly
at the corner of the square.
- I say roughly because some dies are
designed to shift the insert slightly to the left or right of center
to improve bend quality.
- However, this will generally be
less than 1/4". If as in the example above, you placed the
followbar in the wrong hole, the
- insert will be very noticably off
center and almost always to the right of red line 1.
- SQUARE AND RECTANGULAR GROOVE DIES:
- Square groove dies operate similar
to the round groove dies explained earlier with these exceptions:
- 1) The bottom of the groove has a
raised crown machined into it. This starts the depression in the
- side of the tubing during bending
to prevent the tube from kinking and helps keep the sides reasonably
- straight. Note that square tubing
will always sink in on the outside and inside of the bend.
The U-strap clamp uses a bolt to tightly secure the tubing to the
die block. This bolt presses against
- a H shaped steel plate to prevent
- bolt from marring the tubing. To
- right is an illustration of the
- installed in the forming die.
- 3) The followbar does not utilize
- It is machined from one solid
- 4) You must lubricate both the
- of the tubing and the COMPLETE
- groove in the forming die before
- bending. Square tubing tends to
- wedge itself into the forming die
- bending and generally requires a
- large rubber mallet to tap it out
- finished. The bigger the tubing,
- worse the problem. Without
- it can be very difficult to remove
- tubing from the die. This problem
- not specific to the Model 3 Bender,
- but to ALL benders utilizing a one
- piece die.