MODEL 3 TUBE BENDER
Assembly & Operating Instructions
- Die Set Installation and Bending
- There are two types of forming dies
provided for the Model 3 Bender. Those with drive holes and those
without. The drive holes
- are the five 1" holes drilled
in a circular pattern around the forming die's center hole. A
7/8" diameter pin inserts through the drive
- links and through the forming die's
drive holes when in operation. The drive holes are drilled 1/8"
oversize to provide easier pin
- installation. To prepare for
bending, follow the steps below depending on the type of die set.
NOTE: The procedures below
- describe using the degree
indicator. To install an indicator onto your forming die, please
refer to that section earlier in this manual.
- Place the forming die into the
bender using the 1"
- frame pin. If bending square
tubing, thoroughly lubricate
- the forming die's groove. However,
if bending round
- tubing or pipe, NEVER lubricate the
forming die's groove.
- If you do, the tube will tend to
slip backwards in the die
- while bending, which in turn causes
the tubing to kink or
- wrinkle. Place the tube into the
forming Die. Install the UStrap
- with the shorter 7/8" U-strap
pin. If necessary,
- tighten the U-strap bolt to prevent
the tube from slipping
- through the die will bending. It's
a good idea to cut a slice
- out of a bigger piece of tubing
place it between the bolt and
- tubing to prevent the bolt from
dimpling the tubing. If
- bending thin wall tubing
(.065" or thinner) you must
- always use the U-strap bolt.
- Next, using the 7/8" Followbar
Pin, place the Followbar
- into the bender. See page 5 for the
correct way to install the Followbar. Lightly spray some lubricant
on the outside of the tubing
- so that the tubing will slide
through the Followbar easily. Any spray lubricant works well. If you
are bending tubing with a wall
- thickness of .065" or thinner
you may want to skip the lube entirely. This will help the followbar
stick to the tubing during ratchet
and generally helps prevent wrinkling. Make sure all pins are
completely seated in their holes. Failure to do this
- may cause damage to the bender
links or worse yet the operator may slip and fall.
- Place the 1" x 2" box
tube handle over the Swing Lever making sure the Handle is as far
forward as possible on the Swing
- Lever. Rotate the Swing Lever fully
counter-clockwise. Engage the Rachet onto the outer 3/4" drive
link spacer tube. Lightly pull
- on the handle to preload the
tubing. Do not pull hard enough to actually bend the tubing. Using a
free hand, loosen the degree
- plate nut. Rotate the degree plate
until the die's pointer is at 0 degrees and then hand tighten the
nut to secure it into position.
- Now you're ready to bend. Pull on
the handle in a clockwise direction until the Swing Lever cannot
rotate any further. Return the
- Swing Lever to the starting
position. Initially release the Ratchet easily so as not to move the
tubing and minimize spring back.
- Reengage the ratchet and pull
again. When the last Ratchet tooth is reached, return the Swing
Lever to its starting position.
- Remove the 7/8" Drive Pin and
rotate the Drive Links counter-clockwise until the Drive Pin may be
reinstalled through another
- hole in the Bending Die. Be careful
not to move the tube. Now repeat the above bending sequence until
the desired degree of
- bend is obtained. To release the
tubing from the bender, remove the handle from the Swing Lever.
Insert it diagonally through
- the 3/4" drive link spacer
tubes and pull counter-clockwise. The Followbar will release its
grip and the tubing may be removed.
- These dies typically have a center
- radius of less than 3".
Because the radius of
- the die is so small, drive holes
- drilled into the die. This does not
- problem as the tube sizes for these
dies is of
- relatively small diameter and is
- The ratchet is not used.
- Die installation procedure:
- Swing the ratchet assembly out of
- way as shown below. Place the
- into the bender. Place the tubing
to be bent in
- the bender and using the 5
1/4" long drive pin
- (not the shorter U-Strap pin that
- used) install the U-strap. If
- the U-strap bolt to secure the
tubing to the die.
- This is not mandatory and may be
- the tubing shows no signs of
- the die while bending. Now install
the followbar being sure the word 'TOP' is facing up. Rotate the
drive links until their front edge
- pushes directly on the U-strap pin
as shown in figure 6. Place the handle diagonally through the drive
links' two 3/4" spacer tubes.
- Lightly pull on the handle to
preload the tubing. Do not pull hard enough to actually bend the
tubing. Using a free hand, loosen
- the degree plate nut. Rotate the
degree plate until the die's pointer is at 0 degrees and then hand
tighten the nut to secure it into
- position. Now, simply pull the
handle and observe the pointer until the desired degree is reached.
- EXAMPLE BEND
- The first thing you need to do is
to determine the actual starting location of a bend produced by the
Bending Die you installed
- in the bender. This can vary
between die sets and must be checked for every die set purchased. In
the below example we are
- using 1 1/2" O.D. tubing and a
Bending Die with a Center Line Radius of 6 1/2".
- Here's the procedure:
- A) Place a piece of tubing (app. 2
1/2' long) into the bender so that exactly 12" extends out from
the edge of the die to the
- end of the tubing when the tubing
is fully seated in the Bending Die's groove. Place a little bending
pressure on the tube
- so as to seat the tubing in the
Bending Die. Not enough to start bending the tubing just enough to
seat it in the groove.
- NOTE: If you lay a small length of
tubing in the groove of a Bending Die you will notice the tubing
does not seat to the
- bottom of the groove. The Bending
- are deliberately machined this way
- that during the bending operation a
- force is developed in the tubing.
- helps to reduce flat spotting and
- B) Using a Black Magic Marker mark
- on the tubing precisely at the edge
- die. See figure 7.
- C) Bend the tube to an exact 90
- Use a carpenters square to check
- angle. You will have to overbend
- a little to account for springback.
- much to overbend will come with
- If you overbend the tube a little
- Because cold worked steel has
- you can place the tube in a vise or
- else that will retain it, and
- it. Obviously this only works for
- amounts of overbend. If the tubing
- underbent, it will be necessary to
- back into the bender.
- D) With the tube bent correctly to
- locate the actual start of the
bend. To do this, measure from the end of the tube to the far end of
the 90 degree bend.
- In the example in figure 8 this
came out at 20 1/4". Subtract 6 1/2" for the centerline
radius (CLR) of the Bending Die,
- another 3/4" for the radius of
the tubing not seated in the die, and 1/8" for springback.
(Substitute the CLR and tube radius
- to match your die set). The
1/8" figure for springback is an approximation, not an exact
figure. However it is usually very
- close to the real thing and may be
used without worry to determine the actual starting location of the
- Now subtract from the 12 7/8"
the original 12" we had
- marked earlier and you find that
the bend will actually
- start 7/8" in from the edge of
the bending die. Now we
- know for example, if we want
40" from the end of the
- tubing to the start of the bend, we
must subtract 7/8"
- from 40" and set the tubing 39
1/8" from the edge of
- the Bending Die.
- Another example, you want 36"
from the bottom to the
- top of a rollbar. Tube size is 1
3/4" and you have an
- actual bend start 1/2" inside
of the Bending Die's edge.
- The CLR of the Bending Die is 7
1/2". So: 36" - 1/2"
- (Actual Bend start) - 7 1/2" (CLR
of die) - 7/8" (Half of
- the tubing diameter) - 1/8" (Springback)
= 27". Set the
- tube 27" from the edge of the
Bending Die and make
- the bend.
- Example hoop :
- Preparation is the key to making
accurate bends. To make multiple bends in one section of tubing you
will need a universal
- protractor. The protractor is then
clamped, using a machinist v-block and a radiator hose clamp, to the
tube. Make sure the pointer
- indicates '0' before making your
first bend. Also using a carpenter's level, make sure the tube is
entering the bender level. On the
- second bend if you turn the tube so
that the pointer again reads '0' and the carpenter's level indicates
the tube is level, both bends
- will be on the same plane with no
- First step is to draw a sketch of
the intended shape and all measurements. Figure 9 below is the
desired hoop. The Bending Die
- has a centerline radius (CLR) of 6
1/2". The tube O.D. is 1 1/2". We determined earlier,
using the method described on page 4,
- that the Bend Start measurement is
3/4" behind the edge of this particular Bending Die set.
- 1) Determine the total length of
tubing needed. Using a calculator and the formula below let's add it
1/2" (CLR of bend) x 90 (Number of degrees of bend) x .0175 =
Length of tubing used in a bend.
- Using the formula above we get 6
1/2" (CLR of bend) x 90 (Degrees of bend) x .0175 = 10.2375.
Let's round this off to 10 1/4" inches
- (10.250"). This is the amount
of tubing used in the bend. We have two bends so we double this and
get 20 1/2". Add to this the
- straight sections and we get 20
1/2" (tubing in bends) + 27 (the center section) + 13 1/2"
for the left upright + 13 1/2" for the right
- upright = 74 1/2" of tubing
needed. It's usually a good idea to leave a couple of inches extra
on the end. Remember, it's easier
- to remove tubing then to add it. So
let's add 2" to 74 1/2".
- 2) We cut our tube to 76 1/2".
It's generally easier to work from the center out when making two
bends in a tube. Divide 74 1/2"
- by 2 and our center point is 37
1/4" from the end of the tube. Place a mark on the tubing 37
1/4" in from one edge and mark the
- tubing so you will know which side
is the 37 1/4 side and which side is 39 1/4". Notice we didn't
use the 76 1/2" measurement that
- we cut our tubing to. This way we
only have to cut 2" off one end of the finished tube instead of
1" off each end. The first bend
- is made on the short 37 1/4"
- 3) Using the method described on
page 4 we determine that the tube should extend 12 5/8" from
the edge of the Bending Die.
- Below is the equation from page 4.
- 20" (Height of hoop) - 6
1/2" (CLR of die) - 3/4" (1/2 of tube's dia.) - 1/8"
(Springback) - 3/4" (Bend Start) = 11 7/8".
- After making the bend we have half
our hoop completed. The top of the bend is 20" from the bottom
of the tube.
- 4) Now for the other bend. First we
need to determine how much the tube stretched in the bend area. From
figure 9 we see that
- the tube should be 20 3/4"
from the outside edge to our 37 1/4" center mark. However after
measuring from our center mark to
- the outside edge of the bend we now
have 21" and not the planned 20 3/4". This 1/4"
increase is due to springback and the tube
- stretching in the area of the bend.
- If we now repeated the second bend,
using the same 12 5/8" from the end of the tubing + 2" for
the extra tubing we allowed, we
- would end up with a hoop 1/2"
too wide. This is because the 1/4" stretch developed in the
first bend will also be developed in the
- second bend, giving us 1/2"
total increase in width. Not a good deal if you only want a 40"
wide hoop. So what's the solution. Actually
- there is two ways to do it.
- FIRST METHOD:
- Look at figure 9 and notice the
second bend starts at the top of the hoop and not at the top of the
upright as the first bend did. Also
- the start of the second bend is
drawn as 13 1/2" from the center mark. If you take the 13
1/2" measurement and subtract the 1/
- 4" of growth that was
developed in the first bend and another 1/4" to compensate for
the second bend's growth you end up with
- 13". Subtract another
3/4" to account for the 3/4" Bend Start location on the
Bending Die set and we have a final setting of 12 1/
- 4". Notice we did not subtract
an 1/8" for springback. This is accounted for already in the
1/4" we added for the second bend's
- growth. Set the tube so that the
Bending Dies edge is exactly 12 1/4" from the center mark. Make
sure the universal protractor
- reads '0' and the carpenter's level
is centered. As one final check you can also measure from the far
side of the completed bend
- to the edge of the bending die. See
figure 10. This measurement should read:
- 40" (width of hoop) -
3/4" (radius of tube not in bending die) - 1/8" (springback
allowance) = 39 1/8"
- Make the second bend. Measure the
height of the second upright and cut off the extra tubing we allowed
- SECOND METHOD:
- The second method is basically the
opposite of the first method. The second bend will start at the
bottom of the upright and NOT
- at the top of the hoop as in the
first method and as shown in figure 10. We use the same method as
used to bend the first bend
- with a few exceptions. First
calculate the starting point for the second bend as shown below:
- 20" (total height of hoop) - 6
1/2" (CLR of bending die) - 3/4" (Bend Start) = 12
- Add 2" to account for the
extra tubing we allowed earlier. Also add the 1/4" growth
developed in the first bend and another 1/4"
- for the second bend. DO NOT ADD
1/8" SPRINGBACK. Once again this is already accounted for in
the 1/4" growth of the second
- bend. We end up with:
- 12 3/4" + 2" (extra
tubing) + 1/2" (growth for both bends) = 15 1/4"
- Set the tube's end at 15 1/4"
from the Bending Die's edge. Make sure the universal protractor
reads '0' and the carpenter's level
- is centered. Make the second bend.
Measure the height of the second upright and cut off the extra
tubing we allowed for earlier.
- Thank you for purchasing the Model
3 Tube Bender. Any further questions please call.
- © Copyright 2004 by J D Squared