Bend Tooling

Welcome to the industry's only comprehensive resource for the terminology used in rotary-draw tube-bending. The primary objective of the Bend Tooling Encyclopedia is to define the various words and phrases in use in the tube-bending community in order to ensure that even if we are not speaking the exact same language, we do understand each other. The Bend Tooling Encyclopedia™ builds upon the glossary John Gillanders authored in his widely-circulated guide to tube-bending, Pipe and Tube Bending Manual -- and then some. More than a dictionary, it contains extensive articles on key subjects which not only provide definitions but also the concepts, applications, practices, and relationships to other subjects behind the term in question. This internet version of the Bend Tooling Encyclopedia is divided into seven volumes, which are extensively hyperlinked to relate common subjects within the Encyclopedia and elsewhere in the website.

A print of the tube bend, if available. We can also work from an XYZ dataset of the bend coordinates. bullet Tube shape. For example, round, square, rectangular, elliptical, or oval, bullet Orientation of non-round tube bend, either hard-way (major axis in plane of bend) or easy-way (major axis perpendicular to the plane of bend). bullet Outside diameter or outside dimensions of tube. If your request is for pipe, please tell us if you are specifying the true outside diameter or using the nominal IPS or EMT diameter. Similarly, if your request is for copper tube, please tell us if you are specifying the true outside diameter or using the nominal K-type or L-type diameter. bullet Wall thickness. If you are bending laminated tubing, we can specify the mandrel more accurately if you provide us with the thickness of each lamination. bullet Bend radius. Please tell us if you are specifying the centerline radius (typical for round tubes) or the inside radius (typical of non-round tubes). bullet Degree of bend. Unless a special consideration is involved, we recommend that you specify this as either a 90-degree bend or a 180-degree bend to maximize the utility of your rotary-draw tool set for other applications. bullet Tubing material. For example, mild steel, stainless steel, titanium. If your request is for either aluminum or copper tubing, please give us the exact material specification or in the alternative whether the material is hard or soft. These two materials vary widely in hardness, and will change the tools we recommend if in the soft condition. bullet Make and model of your rotary-draw bending machine. We have the mounting specifications for most machines on file. If we don't have the information for your machine, we will send to you blank tool drawings so that you can fill in the basic dimensions for the mountings. bullet If you have not sent us a drawing and your request is for a multiple-bend tubular component, please inform us any mid-tangent restrictions on clamp length. Similarly, advise us if the request is for "bent-leg" U, a serpentine bend, or other multi-bend configuration that will cause clearance problems with your machine. bullet Finally, please tell us if serrations (which improve the grip of short clamps, but the trade-off is marking of the outside surface of the tube) are acceptable or unacceptable.

• tube diameters.875" to 5.563" (22mm to 140mm).
• bending capacity.1-"D"

• tube diameters875
• Materialround tubing

A rotary-draw die set has three components: Bend die, clamp die, and pressure die. The key material requirement for these dies is that they are tough. A tough die has hard working surfaces that can absorb a shock without breaking. So a tough die has some give. It is not brittle. For the same reason we do not use glass hammers, we should avoid materials and heat treatments for bending dies that make them brittle instead of tough and so break instead of wear out. Consequently, the tool steels that are sometimes specified for rotary-draw die sets, such as A2, D2, or even a shock-resistant material like S7, are not the best materials in terms of cost-effectiveness. While they can be heat treated to a high level of hardness, they are designed to hold a sharp edge in metal-cutting operations. So the brittleness that comes with this hardness is acceptable for that use. However, tube-bending is, of course, not a metal-cutting process. There is no need for tooling materials that hold a sharp edge.

Since the introduction of the modern ball mandrel in the 1950's, aluminum-bronze and hard-chrome plated steel have been the most common material specifications. The former has been preferred for ferrous and titanium tubing while the latter for aluminum, copper-based, and, in some cases, mild steel tubing. Even with the advent of remarkable life-extending thermal diffusion and titanium coatings, there remain good reasons for preferring aluminum-bronze and hard-chromed plated steel for mandrel tooling. For example, the primary cause of shortened mandrel life is not the material specification but set-up. The purpose of the mandrel is to maintain the original round, square, rectangular, or other shape of the tubing throughout the arc of the bend. This is achieved by setting the mandrel so that its nose supports the point of bend, at which the tubing material becomes plastic as it is drawn into a bend. Too often the mandrel nose is set behind the point of bend so that the weaker balls and links must do the work of the nose, which significantly shortens the life of these components.