Tube Bender Tooling Definitions

Bend Die

[LINK: Bend Die category] The bend die (also called a radius die, bend form or bending form) is the rotating tool that sets the centerline radius (CLR) of the bend. Its groove is machined to match the profile of the material being bent — round tube, pipe, square tube, rectangular tube, solid bar or custom extrusions. The bend die has two working areas: the radius section, which forms the bend, and the straight clamping section (clamp length), where the clamp die holds the tube. Bend dies are available in one-piece construction or with a replaceable clamp insert so the clamping section can be changed without replacing the entire die.

To quote a bend die, provide: tube OD or profile dimensions, wall thickness, centerline radius, material, maximum bend angle, machine make and model, and machine rotation (left hand or right hand).

Clamp Die

[LINK: Clamp Dies category] The clamp die (also called a clamp block) holds the tube tight against the straight section of the bend die so the tube is pulled around the radius without slipping. Clamp dies are typically two to three times the tube OD in length and can have a smooth, serrated, knurled or grit-coated groove to increase grip. Clamp slippage is a common cause of inconsistent bend angles, marked tube and poor part repeatability.

Pressure Die

[LINK: Pressure Die category] The pressure die (also called a follower die or pressure bar) supports the outside of the tube opposite the bend die and resists the reaction force of the bend. On most machines the pressure die travels forward with the tube during the bend. Pressure die length is generally matched to the length of tube being formed in the bend. Pressure die setting has a direct effect on wall thinning, wrinkling and ovality.

Pressure Die Assist (Pressure Die Booster)

A pressure die assist, or booster, is a hydraulic feature that actively pushes the pressure die forward during the bend instead of letting it simply follow the tube. Pushing material into the bend reduces wall thinning on the outside radius and helps with thin-wall and tight-radius bends. Boosting can cause the pressure die to lift, which is one of the problems self-aligning tooling is designed to control.

Wiper Die

[LINK: Wiper Die category] A wiper die is a stationary tool mounted behind the bend die, fitted to ride in the bend die groove and tapering to a thin, feather-edge tip just behind the tangent point. It fills the gap between the tube and the bend die where the material is being compressed, preventing wrinkles on the inside radius of the bend. Wiper dies are required when bending thin-wall tube, hard materials, tight radii, or profiles that tend to hump or wrinkle. Each wiper die is machined to match the centerline radius of its bend die.

Wiper dies come in two main styles:

• Square back wiper die — a one-piece wiper mounted directly to the machine.
• Tipped (insert) wiper die — a replaceable tip mounted to a separate wiper die holder, so only the worn tip needs to be replaced.

To quote a wiper die, provide: material to be bent, tube OD, wall thickness, centerline radius, wiper style (square back or tipped for a holder), mounting information, and the lubricant in use.

Wiper Die Rake

Rake is the small angle at which the wiper die is set relative to the tube, so the tip contacts the tube at the tangent point and the back of the wiper clears the tube slightly. Correct rake reduces drag, tip wear and scratching while still preventing wrinkles.

Mandrel

[LINK: Mandrels category] A mandrel is an internal support inserted into the tube during bending. Its main job is to support the tube from the inside to prevent flattening, excessive ovality and collapse of the outside wall of the bend. Mandrels are used when the wall factor is high (thin wall relative to OD) or the D of bend is small (tight radius).

Mandrel body material is chosen to suit the tube material:

• Hard chrome mandrels — mild steel, aluminum, 304 stainless, 321 stainless, copper and bronze tubing.
• Ampco bronze mandrels — Inconel, 21-6-9 stainless, titanium and titanium alloys, where a bronze mandrel reduces galling.

To quote a mandrel, provide: tube OD, wall thickness, centerline radius, material, maximum bend angle, number of balls (if known), and mandrel rod thread size.

Plug Mandrel

A plug mandrel (also called a plain or solid mandrel) is a single solid body with no balls. It supports the tube up to the tangent point and is used for heavier-wall tube and moderate bend radii.

Ball Mandrel (Link Mandrel)

A ball mandrel has one or more articulated balls, or links, attached to the mandrel shank. The balls follow the tube into the bend and support it past the tangent point, which is necessary for thin-wall tube and tight radii. More balls provide more support around the bend.

Mandrel Pitch — Standard, Close and Ultra Close

Pitch is the spacing between mandrel balls. Standard pitch is used for general work. Close pitch and ultra close pitch place the balls nearer together to give more continuous internal support for thinner walls and tighter radii.

Formed Nose (Form) Mandrel

A formed nose mandrel has its tip shaped to match the bend radius, giving extra support past the tangent point without balls. It is used for some heavy-wall and moderate-radius applications.

Mandrel Rod

The mandrel rod connects the mandrel to the machine and holds it in position during the bend. Mandrels thread onto the rod, so the rod thread size must be matched when ordering a replacement mandrel.

Collet

[LINK: Collet category] On CNC and NC tube benders, the collet is the gripping tool in the carriage that holds the tail end of the tube. The collet feeds the tube forward between bends (distance between bends) and rotates it to set the plane of the next bend (plane of bend or rotation). Collets are sized to the tube OD.

Self-Aligning Tooling

Self-aligning tooling was originally designed for numerically controlled (NC and CNC) tube benders and works equally well on conventional machines, particularly those with worn tool mountings. Its distinguishing feature is an interlocking rail design: the clamp die and pressure die interlock with the bend die, which keeps the three tools aligned throughout the bend. The pressure die is self-supporting at the bend tangent, and constant alignment helps compensate for machine wear, material inconsistencies, and pressure die lift when a pressure die booster is used. Self-aligning tooling can significantly reduce setup time and scrap.

Self-aligning bend, clamp and pressure dies are made from a range of tool steels and heat treatments. Some self-aligning tooling is made reversible so it can run on both left hand (counterclockwise) and right hand (clockwise) machines. Tool mountings vary by machine manufacturer and model.

Left Hand and Right Hand Rotation

Tube benders bend in either a clockwise (right hand) or counterclockwise (left hand) direction. Bend dies, clamp dies, pressure dies and wiper dies are built to suit the machine’s rotation. Always confirm machine rotation when ordering tube bender tooling.

Bend Die Key

[LINK: Bend Die Keys category] The bend die key (drive key) locks the bend die to the machine’s spindle or bend arm so the die rotates with the machine without slipping. Worn keys and keyways cause tooling movement and inconsistent bends.

Clamp Bar

[LINK: Clamp Bars category] On Pines and similar benders, the clamp bar is the machine component that carries the clamp die and moves it into and out of clamping position against the bend die.

Wear Strip

[LINK: Wear Strips category] Wear strips are replaceable sliding surfaces on the bend arm, carriage or pressure die slide. They take the wear from moving components so the machine castings do not, and worn wear strips are a common source of tooling misalignment.

Toggle Link

[LINK: Toggle Links category] Toggle links are part of the clamping linkage on many Pines hydraulic tube benders. They multiply the force of the clamp cylinder and lock the clamp in position during the bend. Worn toggle links can reduce clamp force and cause tube slippage.