Cold pilgering and cold drawing are both secondary cold-working processes that produce precision seamless tubes from hot-finished mother tubes. They achieve similar outcomes — tighter tolerances, refined grain structure, improved surface finish — but through fundamentally different mechanics, and each process has a distinct performance envelope that makes it the better choice for specific applications.
How Cold Drawing Works
Cold drawing pulls the tube through a fixed die and over a mandrel in a continuous, linear motion. The tube enters one end and exits the other at a smaller OD and WT. Each pass reduces the cross-sectional area by 15–35%, with multiple passes separated by intermediate annealing to restore ductility. The process is fast (draw speeds of 10–40 m/min), efficient for long production runs, and produces tubes with excellent surface finish and good dimensional control.
Cold drawing excels in the mid-range of seamless tube production: OD 10–168 mm, WT 1–14 mm, in carbon, alloy, and stainless steels. It is the volume production process for heat exchanger tubes, hydraulic tubes, boiler superheater elements, and instrumentation tubing. OD tolerances of ±0.10–0.25 mm and WT tolerances of ±10% are standard for cold-drawn tubes.
How Cold Pilgering Works
Cold pilgering uses a pair of grooved dies mounted on a reciprocating ring die carrier that rocks back and forth over the tube while a tapered mandrel controls the bore. With each stroke, the dies compress a short section of tube, reducing the OD and WT incrementally. The tube advances and rotates by a small amount between strokes, so the entire circumference and length are progressively worked.
The pilger process achieves higher area reductions per pass than drawing — typically 50–80% versus 15–35% for drawing. This means fewer passes and fewer intermediate anneals to reach the final dimensions, which reduces total processing cost for large reductions. More importantly, the compressive deformation mode of pilgering (versus the tensile mode of drawing) allows the production of very thin-walled tubes with OD/WT ratios exceeding 25:1 that would fracture during conventional drawing.
Where Pilgering Outperforms Drawing
Cold pilgering’s compressive mechanics and high single-pass reduction capability make it the preferred process for thin-wall precision tubes where OD/WT ratios exceed 20:1, large-reduction applications where the mother tube is significantly larger than the finished tube, premium materials (nickel alloys, titanium, zirconium) where minimising the number of annealing cycles preserves microstructural quality, nuclear fuel cladding tubes where extreme dimensional precision and concentricity are mandatory, and aerospace hydraulic tubing where weight optimisation demands the thinnest possible walls at guaranteed tolerances.
Pilgered tubes typically achieve OD tolerances of ±0.05–0.10 mm and WT tolerances of ±5–8%, with eccentricity below 5% — tighter than cold-drawn equivalents across all parameters.
Where Drawing Outperforms Pilgering
Cold drawing is faster, simpler, and more cost-effective for standard-wall tubes in production quantities. For tubes with OD/WT ratios below 15:1 in carbon, alloy, and standard stainless grades, cold drawing delivers adequate precision at 10–20% lower cost than pilgering. The continuous linear process is also better suited to very long tube lengths (up to 30+ meters), which are difficult to achieve on a pilger mill due to the reciprocating stroke length limitation.
Making the Choice
If your tube has standard wall thickness in a common grade and you need ±0.15 mm OD tolerance, cold drawing is the cost-effective choice. If your tube has thin walls, is made from a premium alloy, requires ±0.05 mm OD tolerance or better than ±5% eccentricity, cold pilgering is the process that delivers.
Need precision tubes by either process? Send us your specification and we will recommend the optimal manufacturing route.