Tube Bending Services
Custom round-tube bending: collected size envelope and tolerance standards for drawn and mandrel bending, process selection, and what to send for a quotation.
Last updated: 2026-10-29
Tube bending turns straight round-tube stock into frames, roll bars, exhaust runs, handrails and fluid lines — in one piece, without welded elbows. The commonly tooled envelope for drawn and mandrel bending runs from quarter-inch tube up to two-inch, across stainless, structural aluminium and alloy steels; within that window, computer-guided bending holds line and angle repeatable enough for production, not just one-offs.
The process decision is really about wall and radius. Thin walls, large diameters and tight radii are where tubes collapse, kink or oval — which is what mandrel support exists for. Simple single bends tolerate cheaper methods; multi-bend parts with consistent center-line radii are where CNC rotary-draw bending earns its setup.
Specifications
| Property | Value | Condition |
|---|---|---|
| Min outer diameter | 0.250 in | minimum bendable round-tube diameter (drawn or mandrel bending) |
| Max outer diameter | 2.000 in | maximum bendable round-tube diameter (drawn or mandrel bending) |
| Wall thickness range | 0.035–0.188 in | bendable wall range; material table: 304/316 stainless and 6061 aluminum to 0.188 in max, 316 stainless to 0.120 in |
| Linear tolerance | ±0.010 in | linear dimensions excluding locations to bends; multi-planar bends ±0.030 in; single planar bends ±0.010 in |
| Angularity tolerance | ±2° | bend angularity; center line radius tolerance ±0.125 in typical |
| Clr ratio | 2:1–5:1 (recommended) | bend radius to tube OD ratio using center line radius; CLRs under 2× OD carry higher manufacturing risk |
| Materials | 304 / 316 stainless, 6061 aluminum, 4130 alloy steel, A513 (DOM / HREW / CREW) | round tube stock, welded or seamless per alloy |
| Max part envelope | Not established in the collected evidence — confirm at quotation. | |
| Lead time | Not established in the collected evidence — confirm at quotation. | |
| Min batch size | Not established in the collected evidence — confirm at quotation. | |
Values above are rendered from the collected model-evidence layer, each carrying the heat-treatment condition it was reported under; fields without collected evidence are stated as not established rather than estimated. Requirements outside the table are confirmed for the specific geometry and batch at quotation.
Applications & Selection Points
Frames, racks and structural loops
Vehicle and equipment frames, roll cages, furniture loops and handle bars are the classic territory: multiple bends per part, appearance matters, and a continuous tube is stronger and cleaner than joints. Designing every bend on the same center-line radius is the single biggest manufacturability lever on these parts — it lets the whole part run without re-tooling between bends.
Fluid and gas lines
Exhaust runs, hydraulic lines and process tubing need the bore preserved through the bend, which is mandrel work: internal support keeps the section round where the tube would otherwise flatten. State the medium and pressure on the RFQ — it decides how much wall and how much support the bend needs.
When bending is the wrong route
Tight radii below twice the tube diameter invite wrinkles and thinning; cut features — holes, slots, copes — belong to tube laser cutting before or after forming; and very large, gradual sweeps may suit roll bending instead of tool-based drawing. Mixed features usually sequence cutting first, bending second, end operations last.
Tolerances that survive the process
Linear dimensions away from bends and simple single-plane bends carry the tight standard tolerance; multi-plane parts and angularity carry looser standards. Design the datums so the critical interfaces measure from the tube ends, not across bends, and put the tight callouts only where function demands them.
Frequently Asked Questions
What bend radius should my tube part use?
Hold the center-line radius at or above twice the tube diameter — the commonly available combinations cluster in the two-to-five times band. Tighter radii are possible with mandrel support but raise wrinkling, thinning and tooling cost. On multi-bend parts, use one radius throughout: every distinct radius adds a tool and a setup.
Why did my bent tube flatten or crack?
Flattening means the section lost its support through the bend — thin wall, big diameter or tight radius, without mandrel backing. Cracking points at the material side: wrong temper, seam orientation on welded tube, or a radius below what the alloy tolerates. Both are design-stage questions; a bend-feasibility note with the RFQ gets them answered before tooling is cut.
What should I send for a tube bending quote?
A 3D model or dimensioned sketch with the tube diameter, wall, center-line radius per bend and the angles between bends; the alloy and temper; end conditions and any cut features; and quantity. Multi-bend parts benefit from a bend table — the datum scheme and inspection intent on critical interfaces decide tolerance proposals.
Ordering & Documentation
Documents
Send a model or drawing with tube OD, wall thickness, center-line radius and bend angles called out per bend, plus the alloy and whether seamless or welded stock is acceptable. End features — threads, flares, copes — belong on the same document so the process sequence prices as one job.
Quotation
A quote is priced from the tube specification, bend count and radii, tooling needs, cut features, finish and quantity. One center-line radius across the part usually prices better than several; mandrel work on thin walls is worth flagging explicitly rather than discovering at first article.
Sample & Supply
First articles are standard practice on tooled bends — the sample validates radius, springback compensation and datum scheme before the batch. Production runs hold angle and line consistently once setup is proven; agree the inspection points at quotation.
Finishing & Shipping
Bent tubes ship with cut ends deburred and finish as specified — mill, brushed, plated or powder coated. Long parts need sleeve or crate packing to protect the bends in transit; state length and destination so the packing plan fits the freight.