Insights · Reference
A single side-by-side reference for spiral duct machines (round-duct tubeformers): diameter range, cutting method, material gauge, drive power and weight. The figures below are taken verbatim from the SBKJ Product Catalog 2026 — use the table to shortlist the right machine for your duct range and output.
Every spiral duct machine forms round duct from a continuous galvanised, stainless or aluminium strip (137 mm standard) by spiral-winding and lock-seaming it into a tube. What separates the models is the maximum diameter, how the finished tube is cut, the material gauge they can roll, and the drive power and footprint that follow. This table compares the four machines in the SBKJ SBTF spiral series head-to-head.
| Specification | SBTF-1500 | SBTF-1500C | SBTF-1602 | SBTF-2020 |
|---|---|---|---|---|
| Round-duct diameter | Φ80–Φ1500 mm | Φ100–Φ1500 mm | Φ80–Φ1600 mm | Φ80–Φ2500 mm |
| Cutting method | Saw blade | Plasma + saw blade | Plasma + flying slitter | Flying slitter + auto length |
| Galvanised steel gauge | 0.4–1.2 mm | 0.4–1.2 mm | 0.4–2.0 mm | 0.4–2.0 mm |
| Stainless steel gauge | 0.4–0.8 mm | 0.4–1.2 mm | 0.4–1.2 mm | 0.4–1.2 mm |
| Aluminium gauge | — | — | 0.4–3.0 mm | 0.4–3.0 mm |
| Lockseam strip width | 137 mm | 137 mm | 137 mm | 137 mm |
| Drive power | 5.5 kW + 4 kW saw | 5.5 kW + 1.2 kW saw + 7.5 kW plasma | 15 kW + 0.25 kW pump | 22 kW + 0.25 kW pump |
| Machine weight | 1700 kg | 2500 kg | 5000 kg | 4500 kg |
| Continuous (no-stop) cutting | No | No | Yes | Yes |
| Best fit | Entry-level round duct, light gauge | Mixed GI/stainless, clean plasma cuts | High-throughput commercial | Large-diameter + industrial |
Source: SBKJ Product Catalog 2026, manufacturer nameplate specifications. Round duct conforms to EN 1506 / SMACNA round-duct construction. Diameters are the machine's forming range; achievable gauge depends on material temper.
Three variables decide the machine, in this order:
1. Maximum diameter you need to produce. If your largest round duct is ≤ Φ1500 mm, the SBTF-1500 or 1500C covers it. Up to Φ1600 mm needs the SBTF-1602. For large-bore industrial, mining-ventilation or tunnel duct up to Φ2500 mm, the SBTF-2020 is the only machine in the range that reaches it.
2. Material and gauge. Light commercial galvanised work (0.4–1.2 mm) runs on any model. If you roll heavier galvanised up to 2.0 mm, stainless above 0.8 mm, or aluminium, you need the SBTF-1602 or 2020 — only those two carry the 0.4–2.0 mm GI and 0.4–3.0 mm aluminium rating.
3. Output / continuity. Saw-blade machines stop the tube to cut; a flying slitter cuts on the move so the line never pauses. For a workshop that runs round duct all shift, the continuous-cut SBTF-1602 or 2020 will out-produce a saw-blade machine of the same diameter class by a wide margin. For occasional or jobbing round-duct work, the SBTF-1500 is the lowest-capital entry.
Saw blade — the spiral tube is formed, the machine stops, a circular saw cuts to length, then forming resumes. Lowest cost, lowest throughput, fine for light gauge.
Plasma — a plasma torch cuts the tube cleanly, which matters on stainless and heavier galvanised where a saw leaves burrs. The SBTF-1500C pairs plasma with a saw so the operator can choose per job.
Flying slitter (flying shear) — a cutting head travels with the tube and cuts it while the machine keeps forming, so the line never stops. This is what makes the SBTF-1602 and SBTF-2020 continuous-production machines rather than batch machines, and it is the single biggest throughput differentiator in the spiral category.
Machine weight and drive power scale with capability: the entry SBTF-1500 is 1700 kg on a 5.5 kW forming head, while the continuous SBTF-2020 is 4500 kg on a 22 kW drive. Heavier, higher-power machines need a stronger floor, a larger electrical supply (most run 380 V 3-phase; 60 Hz on request) and more floor space — factor the footprint and power budget into the workshop layout, not just the machine price. SBKJ provides a 2D workshop layout drawing with every quotation so the line, uncoiler and run-out table are sized to the available floor before you commit.
Get a spiral machine recommendation in 12 hours →
Across the SBKJ SBTF series, round spiral duct ranges from Φ80 mm to Φ2500 mm. The SBTF-1500 covers Φ80–Φ1500 mm, the SBTF-1500C covers Φ100–Φ1500 mm, the SBTF-1602 covers Φ80–Φ1600 mm, and the SBTF-2020 covers Φ80–Φ2500 mm. All run from a 137 mm lockseam strip.
The SBTF-1602 and SBTF-2020 handle the widest gauge: galvanised steel 0.4–2.0 mm, stainless steel 0.4–1.2 mm and aluminium 0.4–3.0 mm. The lighter SBTF-1500 and SBTF-1500C are rated for galvanised 0.4–1.2 mm and stainless 0.4–0.8 / 0.4–1.2 mm.
Saw-blade cutting stops the tube to cut (lowest cost). Plasma cutting adds clean cuts on stainless and heavier galvanised. A flying shear / flying slitter cuts the tube while it keeps forming, so the line never stops — the highest-throughput method, used on the SBTF-1602 and 2020.
In the SBKJ SBTF series, weight ranges 1700–5000 kg and drive power 5.5–22 kW. The SBTF-1500C adds a 7.5 kW plasma supply; the SBTF-1602 and 2020 add a 0.25 kW cooling-water pump. Most run 380 V 3-phase, 50 Hz (60 Hz on request).
Not sure which spiral machine fits your duct range and output? An SBKJ mechanical engineer replies within 12 hours — not a salesperson.
Ask an engineer