Tubing mills are the small-to-medium end of the ERW family: lines that turn narrow strip into tube for furniture, bicycles, heat exchangers, scaffolding and general purpose pipe. They live or die on changeover speed, so the tooling design matters as much as the mill itself.
What a Line Includes
- Uncoiler, shear and butt welder and strip accumulator.
- Forming and sizing mill with roll tooling designed for your tube.
- HF welder, cooling section and flying cold saw cut-off.
- Run-out table, stacker and strapping as required.
We build the roll tooling, the seam welder and the cut-off in our own workshops, so a tubing mill arrives as one coordinated system rather than parts from four companies. Send your size range and output target to start.
Tube and Pipe Are Two Different Businesses
A tubing mill and a pipe mill are the same machine aimed at different customers. Pipe is sold by the metre against a published standard. Tube is sold by the piece against a drawing, and the drawing is where the cost lives. A mill that makes excellent pipe can be the wrong mill for tube, because tube buyers measure things pipe standards never mention.
| Pipe | Tube | |
|---|---|---|
| Sold against | A standard (EN, ASTM, API) | A drawing or a customer specification |
| Decides acceptance | Wall tolerance, pressure, marking | OD, wall, ovality, straightness, surface |
| Testing | Hydrostatic, NDT on the weld | Dimensional, eddy current, visual, sometimes ID |
| Priced as | Cost per tonne | Cost per piece, or per metre of a finished part |
| Failure cost | A rejected bundle | A stopped assembly line at the customer |
Where Precision Tubing Actually Goes
- Automotive: exhaust systems, seat frames, steering columns, shock absorber bodies, drive shafts.
- Furniture and consumer goods: chair frames, bed frames, trolley handles, display stands.
- Heat transfer: condenser and heat exchanger tubes, where ovality matters as much as wall.
- Fluid power: hydraulic and pneumatic lines, where the inside of the tube is a working surface.
- Machinery: roller shells, printing rollers, conveyor rollers — roundness and wall concentricity decide whether the part spins true.
Each of those asks for something different. An exhaust tube wants a tight bend radius and a weld that will not split when it is bent. A hydraulic line wants a clean inside and no internal bead. A roller shell wants concentricity. One mill configuration does not deliver all three, and a supplier who says it does has not asked enough questions.
The Tolerances That Decide the Machine
| Property | Commercial pipe | Precision tube (typical) |
|---|---|---|
| Outside diameter | ±0.5% or ±0.5 mm | ±0.10 to ±0.15 mm |
| Wall thickness | ±10% | ±5% to ±8% |
| Ovality | Not normally specified | Within the OD tolerance band |
| Straightness | 1 mm per metre | 0.5 mm per metre, or better |
| Cut length | ±5 mm | ±1 mm |
| Internal bead | Scarfed, height not specified | Scarfed flush, checked with a gauge |
Every line in that right-hand column costs money. Tightening OD from ±0.5 mm to ±0.15 mm means more sizing stands, better roll condition and a mill that is re-aligned on a schedule rather than when a complaint arrives.
Straightness Is a Roll Problem, Not a Saw Problem
When tube comes off the line bowed, the first suspect is usually the saw or the run-out table. It almost never is. Bow comes from unequal forming between the top and bottom of the pass, from a sizing stand that is pushing harder on one side, or from cooling that pulls the weld side differently from the rest of the circumference. Straightening rolls or a planisher can hide it; they cannot remove the residual stress, and the bow comes back when the tube is cut or bent.
Ovality and the Finishing Pass
Ovality is decided in the last two stands, and the last stand can only correct what the one before it left. A finishing pass that is worn 0.05 mm out of round will produce oval tube no matter what the gauge says, and the operator compensates by over-tightening, which marks the surface and shortens roll life. This is why tubing mills run shorter roll campaigns than pipe mills and why roll wear should be measured against the original profile, not judged by eye.
Inside the Tube: Internal Scarfing
An ERW tube has a weld bead inside it. For pipe this is often acceptable; for tube it usually is not, because the inside is either a flow path or a surface that another part slides through. Internal scarfing tools cut the bead flush as it leaves the weld rolls, and the knife is the part that fails first: a chipped knife leaves a ridge, a dull knife tears rather than cuts, and a mis-set knife removes wall instead of bead. Knife height, tool clearance and cooling are the three settings to write on the setup sheet.
Downstream Operations Change the Specification
- Cold drawing — reduces OD and wall and improves tolerance and surface, but the starting tube must be concentric or the drawn wall will be eccentric.
- Annealing or bright annealing — needed after drawing; the mill’s job is to deliver a tube with consistent wall so the furnace setting holds.
- Cutting and deburring — a square, burr-free cut from the flying saw saves a second operation.
- Eddy current testing — catches weld defects that a visual check will never see, and it needs a stable, straight tube to work.
Configuring a Tubing Mill for Tight Work
- Two extra sizing stands compared with a pipe mill of the same diameter.
- Polished rolls and a roll cleaning routine, because surface defects are rejects in tube.
- Internal scarfing tooling sized to the wall, with a spare knife holder.
- A flying cold saw rather than a friction saw — a burnt end is a scrap piece.
- A coolant system with temperature control, because thermal growth moves the pass line.
Tell us the tolerance you have to hold and the operation that follows the mill. The configuration follows from those two, not from the diameter alone.
From the Knowledge Centre
- Why a Tube Mill Loses Size After the First Hour
- Reading Roll Wear: When to Resharpen and When to Replace
- From Flower Pattern to Finished Pass
Related Products
Looking for something close to this? ERW tube mill line · Roll tooling · Flying cold saw · Spare parts.
