A bent tube part that’s easy to make is cheaper, ships sooner and holds tolerance better. Most of that is decided on the drawing before it ever reaches a tube bender. This checklist covers what we look for at TBC Metalworks when a new part comes in for quote.
1. Choose a centerline radius (CLR) the shop already has
Every rotary draw bend needs a bend die for that exact tube size and radius. If your design can use a radius the shop already has, you avoid new tooling cost and lead time. Ask for the shop’s tooling list before you finalize the design. As a general rule, a CLR of about 2× the tube OD or more is easier to bend cleanly than a tight 1× OD bend, especially in thin wall.
2. Use one radius throughout the part
A part with the same CLR at every bend can be made in one setup. Mixing radii on one part may need stacked tooling or extra setups.
3. Leave straight length between bends
The bender has to grip the tube between bends. Back-to-back bends with little or no straight between them may need special tooling or may not be possible. If two bends must be close, show the minimum straight you can live with and ask what the shop can do.
4. Mind the straight length at the tube ends
The clamp also needs some straight length at the start of the part. A bend that starts right at the end of the tube may need extra length that’s trimmed off later, which adds cost.
5. Match wall thickness to the radius
Thin wall on a tight radius needs mandrel support and can still wrinkle or go oval. If the bend is tight, a slightly heavier wall or a larger radius often fixes it.
6. Specify the material completely
Call out the specification, grade and temper, for example A513 carbon steel, 304 stainless, or 6061-T6 aluminum. Temper and grade change springback and how tight a bend can go before cracking.
7. Dimension the part the way it will be measured
Dimension to the tube centerline at bend intersections, or provide XYZ coordinates or a 3D model. Tell us which features are critical to function, such as mounting holes, mating ends and overall envelope, and allow realistic tolerances on the rest.
8. Set realistic tolerances
Tight tolerances on every dimension add inspection time and cost. Put tight tolerances where the part mates with something and standard tolerances elsewhere.
9. Mark cosmetic surfaces
If the part is polished, plated or visible, mark which surfaces are cosmetic so the shop can plan tooling and handling around them.
10. Include everything that happens after the bend
End forming, coping, holes and slots, threading, welding, polishing and coating all affect the order of operations. Putting them on one drawing lets one supplier quote and make the whole part.
What to send for a fast quote
- PDF drawing with tolerances and revision level
- STEP file or other 3D model, if you have one
- Material specification, grade and temper
- Annual volume and typical release quantity
- Finish and coating requirements
TBC Metalworks in Green Bay, Wisconsin bends round, square and rectangle tube, pipe and rod in carbon steel, stainless, aluminum and copper, with welding and finishing in-house. Send your drawing through our quote form and we’ll reply within one business day. See also mandrel bending vs. roll bending and our tube bending specifications.