Many times it is important to define terms in order to understand how to plot an
answer. Here is how Hines Bending defines some commonly used terms in the pipe
and tube bending industries. For easy access, click on the term:
• Bend Types
• Centerline Radius (CLR)
• CNC Mandrel Bending Machine
• CNC Push Bending Machine
• Dual Stack CNC Bending Machine
• Exhaust Bends Easy Way
• Hard Way
• Induction Bending Machine
• Leaf Style Bending Dies
• Mandrel Bending Dies
• Mandrel Extractor
• Minimum Tangent
• NC Mandrel Bending Machine
• Rotary Draw Mandrel Bending Die Extractor
• Stack Dies
• Typical Materials used in Mandrel Bending
• Wall Thickness
Bends Types: J Bends,
180 D Bends, 1 D Bends: These are all Rotary Draw Mandrel Bending Terms. They
are mostly talked about in the truck exhaust, truck stacks and other automotive
mandrel and rotary draw bending tube and pipe exhaust applications.
Centerline Radius (CLR): Is the
measurement of the tube or pipe radius that you will be mandrel or rotary draw
bending. This is the distance in mm or inches from the center of tube or pipe
curvature to the centerline axis of the pipe or tubing that you will be mandrel
bending, or rotary draw bending.
Here is an easy way to determine the CLR:
1. If you have a sample tube or pipe part that you
want to mandrel or rotary draw bend available,
place the tube or pipe that you want to mandrel
bend on a large piece of paper or cardboard on
2. Trace the tube or pipe that you would like to
mandrel bend onto the cardboard, continuing the
pattern until you have made a full circle with the
tubing or pipe that you are working with.
3. Measure (in mm or inches) from the center of the
tubing or pipe to the center of your drawn circle.
This straight line measurement to the pipe or
tubing is the centerline radius of your tubing you
want to rotary draw or mandrel bend.
CNC Mandrel Bending Machine (CNC):
Computer Numerically Controlled Rotary Draw mandrel tube and pipe bending
machines; all CNC machines are 3-axis.
CNC Push Bending Machine: A style of bending where the bend
arm is moved positive a few degrees, then the tube is pushed through a set of
rollers to create the bend. This can easily achieve a very large radius bend
compared to rotary draw bending.
Push bending uses a roller on the clamp die assembly with an opposing roller
that is placed where the bend die in a rotary draw bender is normally placed.
This roller can vary in size compared to the other rollers in the die assembly.
Two more rollers of the same centerline radius as the front clamp roller are on
the pressure die assembly. All four rollers rotate freely. A 3D-shaping is
possible. The profile is guided between bending-roll and supporting-roll(s),
while being pushed through the tools. The position of the forming-roll defines
the bending radius. To change the bending plane, a pusher rotates the tube
around its longitudinal axis.
Degree: Angle in degrees for rotary draw mandrel tube
bending is formed. For example, 45 degrees of tube or pipe mandrel bending, 90
degrees of tube or pipe mandrel bending, or 180 degrees of tube or pipe mandrel
Dual Stack: When two different bend radii are required on
the same piece of tubing or pipe.
Easy Way (EZ): This is bending the workpiece on its short
side during the mandrel bending process; bending of a rectangular tubing or
Hard Way (HW): Bending of a rectangular tubing or pipe.
This is bending the workpiece on its long side during the mandrel bending
Induction Bending Machine: A fully automated process of
bending which uses an induction heating coil to create a narrow,
circumferential, heated band around the material to be bent.
When the appropriate temperature is reached, the heated material is shaped into
a bend as it is pushed forward through the coil at a consistent speed and
temperature. After the material passes through the coil, it is cooled by forced
air or water spray, or it may be allowed to cool naturally at ambient
FIGURE 1 ILLUSTRATES HOW TO DETERMINE THE CENTERLINE RADIUS (CLR); SEE
DEFINITION FOR INSTRUCTIONS. FIGURE 2 ILLUSTRATES HOW TO DETERMINE THE
TUBE RADIUS CLR.
J - Bends: J bends are
normally tubes or pipes that have tight radius mandrel bends for the
Exhaust Industry. Exhaust Headers use mandrel J bends.
Mandrel Bending of tubes and pipes that require tight radius bending for
Truck Exhaust Industry.
Bending Dies: Using Square or rectangular bending dies for
pipe or tubing, Leaf Style dies are an easy way to remove the tubing or
pipe that has been through the bending process. The leaf built in to the
bending dies can easy remove the tubing or pipe from the bending die
with little effort.
Tubing and pipe bending dies designed specifically for tubing and
pipe that must need a mandrel for supporting the inside of the pipe or
tubing being bent along with a wiper die to keep the inside of the
tubing or pipe being bent smooth on the inside as well as the exterior
of the pipe or tubing going through the bending process.
Device attached at the rear of a rotary draw mandrel bender to remove
the mandrel after the bending of the tube or pipe has taken place. While
the tube or pipe has finished the bending process and still has the
clamp die holding the tube or pipe, the mandrel is extracted from the
The minimum straight portion of the tubing or pipe that you are mandrel
bending required by the tube or pipe bending machine to form the bend
and maintain the shape of the pipe or tubing being bent.
Mandrel Bending Machine (NC):
Numerically Controlled Rotary Draw Mandrel tube and pipe bending
Rotary Draw Mandrel Bending
Direct Die Actuator: This is an accessory that when bending
shapes will allow the bending die to split in half to release the tubing
or the pipe that is being bent. It is used quite often when bending
tubes and pipes in the exercise equipment business as well as many other
Stack Dies: Used
when two different bend radius are required on the same piece of
tubing/pipe on CNC Pipe and tube bending application.
Tangent: The straight
portion of tubing or pipe on either side of arc that is being rotary
drawn mandrel bent. Normally it will be the section of the pipe or
tubing that you are mandrel bending that is in the clamped area.
used in Mandrel Bending: Aluminum thin and heavy wall pipe
and tubing, Stainless Steel thin and heavy wall pipe and tubing, Copper
pipe and tubing thin and heavy wall, Brass pipe and tubing thin and
heavy wall, Chrome Molly pipe and tubing heavy and thin wall, Aluminized
pipe and tubing, heavy and thin wall, many other carbon steel alloys of
pipe and tubing not mentioned.
The thickness is in mm or inch measurement of the tube or pipe being
mandrel or rotary draw bent, whether it be round tubing being mandrel or
rotary draw bent, square tubing, heavy or thin wall being mandrel or
rotary draw bent, or rectangular pipe or tubing rotary drawn mandrel
bent material. All and any other shapes of pipe or tubing that will need
mandrel or some type of rotary draw bending.