Tools and products for bending and end forming tube and pipe

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Tube bending guide

Glossary of terms used

Captive Lip
Tooling in which the groove in the bend die and wiper die is deeper than the diameter of the tube. Used only with interlock tools in high precision aerospace applications. Minimizes tool marks from the bend die in ultra thin wall applications.
Carbide Coating
Surface treatment to bend die and clamp die grip sections to help prevent tube slippage.
CCW - Counter Clock Wise
On a rotary draw tube-bending machine the rotation of the swing arm. Also referred to as left hand rotation.
CLH - Center Line Height
On a bending machine, the height from the bottom of the bend ide to the center of the tube groove.
CLR - Center Line Radius
Radius along the centerline of the tube to be bent.
Compound Tooling
Tooling that has very short DBB (distance between bends) requires the bend die grip section and the clamp die have the previous bend machined into them. Tooling is expensive but more practical than short grip sections in high production applications.
CW- Clock Wise
On a rotary draw tube-bending machine the rotation of the swing arm. Also referred to as right hand rotation.
D of bend
Formula = The centreline radius divided by the tube O.D. (outside diameter)
DBB - Distance Between Bends
The distance between the tangent of one bend and the tangent of another bend.
DOB - Degree Of Bend
The number of degrees a tube is to be bent.
Easyway
Refers to the direction of bend for rectangular tubes. The tube stands vertically when placed into the bend die.
Galling
The transference of one material to another caused by high pressure and friction. Occurs when stainless steel is bent with a steel mandrel and wiper die: or when aluminum is bent with aluminium bronze tools. Can be reduced by using better lubricants, alternative materials, or a slow arm rotation may help.
Hardway
Refers to the direction of bend for rectangular tubes. The tube lies horizontally when placed in the bend die.
Integral Grip
If a bend die has a removable grip section, it is the straight portion of the groove between the grip and the tangent point.
ISR - Inside radius of bend
Typically used when specifying radius to bend rectangular and square tube.
Knurl
Surface treatment to bend die grip section and clamp die to prevent slippage. Fine and coarse knurls are available. Does not deform the tube the way serration does.
Mandrel
A mandrel is a tool inserted into a tube to prevent the outside part of a tube from collapsing. Mandrels are available in different materials depending on the application. Hard chrome plated steel. Aluminum Bronze. Special coatings.
Mandrel - Thin Wall
Mandrel used for bending thin walled tubing. Utilizes smaller links thereby moving the ball segments closer together to provide better support of the outside wall of a tube.
Mandrel - Ultra Thin Wall
Mandrel used for bending ultra thin walled tubing. Utilizes smaller links thereby moving the ball segments closer together to provide better support of the outside wall of a tube. Links are two sizes smaller than standard links.
Mandrel Extractor
The hydraulic cylinder that removes the mandrel from the tube after bending. Necessary only when a mandrel is being used.
POB - Plane of bend
Refers to the amount of tube rotation between two bends. Specified in degrees.
Pressure Die Assist
A hydraulic cylinder attached to the pressure die master bar. It forces the pressure die to push the tube during bending. This action reduces the collapse and wall thinning and improves ovality of the tube by forcing more material to the areas of the tube where it is stretching and thinning out during bending.
Radial Growth
After a tube is bent, it will springback and the radius of the tube will grow. It will be larger than the bend die CLR. Radial growth is greatest with CLRs greater than four time the tube OD and when bending harder materials.
Reverse Interlock
Tooling that utilizes an interlocking design in which the wiper die, clamp die, and pressure die fit into the bend die. Used primarily for cosmetic or aerospace parts and high production bending. Helps align the tube groove.
Serration
Surface treatment to the bend die grip section and clamp die to prevent tube slippage. Usually used with grip section shorter than three times the tube OD (outside diameter). Tube deformation should be expected.
Springback
When a material is bent it has a tendency to want to return back to its original position (shape). The amount that it does actually return is called springback. The springback amount will differ depending on the material being bent and the CLR on which it is bent.
SurfAlloy
Special process for applying a coating, generally carbide, to the working area of a bend die insert and clamp die to prevent the tube from slipping during bending.
Tube ID
Inside diameter of tube.
Tube OD
Outside diameter of tube.
Wall
Wall thickness or gauge of tube or pipe.
Wall Factor
Formula = Tube OD divided by wall thickness.
Wiper Die
A wiper die is a tool used to prevent wrinkles on the inside radius of a tube during bending.