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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 its circumference.

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.

 

2) U-Strap

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

die.

The front 0 degree insert has a chamfer machined

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 bottom

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.

2) 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 the

bolt from marring the tubing. To the

right is an illustration of the tubing

installed in the forming die.

3) The followbar does not utilize inserts.

It is machined from one solid piece.

4) You must lubricate both the outside

of the tubing and the COMPLETE

groove in the forming die before

bending. Square tubing tends to

wedge itself into the forming die while

bending and generally requires a

large rubber mallet to tap it out when

finished. The bigger the tubing, the

worse the problem. Without lubricant

it can be very difficult to remove the

tubing from the die. This problem is

not specific to the Model 3 Bender,

but to ALL benders utilizing a one

piece die.