Steel tubing with full inner and outer diameter dimensional control
The OPTIM range is an exclusive Delmàs development: a hybrid between the outer precision of the PREMIUM range and the inner control of the PRECISE range. It simultaneously controls outer diameter, inner diameter and weld bead, delivering the technical result most industrial applications need at a cost that makes them viable.
When the axle rotates inside the tube, the weld bead changes everything.
When a welded steel tube is manufactured, the weld inevitably creates a small bead on the inside of the tube. In standard market tubing, this bead can reach 0.5 mm or more. In Delmàs's OPTIM range, it is controlled to a maximum of 0.15 mm. That one-and-a-half tenths of a millimetre is the difference between a mechanism that works and one that fails.
Why ≤ 0.15 mm matters
When a metal axle rotates inside the tube — in an industrial wheel, in a trolley mechanism, in a vehicle seat — a 0.5 mm bead causes misalignment, friction, vibration and wear from the very first cycle. A bead controlled to 0.15 mm prevents all of that.
From steel coil to tube with inner and outer control.
Five steps controlled in-house: from base steel to certified delivery, with bead measurement included.
Raw material
Steel coil selected by grade, surface finish and mechanical properties according to the application.
Precision welding
Controlled ERW process. The seam is formed and controlled in-process from the very first millimetre.
Outer calibration
Outer dimensional control with ±0.05 mm tolerance on nominal diameter.
Inner control · Bead
Proprietary Delmàs process: the inner weld bead is controlled to max. 0.15 mm in every batch.
Certified delivery
Certificate with composition, mechanical properties, verified dimensions and bead measurement.
The only tube on the market with simultaneous outer and inner control.
The OPTIM range combines EN 10305-3 (outer control) and EN 10305-2 (inner control) into a single exclusive Delmàs product.
| Parameter | OPTIM Specification | |
|---|---|---|
| Manufacturing process | Precision welded and calibrated steel tubing · Exclusive Delmàs manufacture · ±0.05 mm | |
| Product definition | Technical co-design: we jointly define a specific technical data sheet to ensure the solution perfectly fits the client's needs. | |
| Outer diameter (OD) | 3 mm – 10 mm (including non-standard sizes: 7 mm, 8.1 mm, 9 mm…) | |
| Dimensional control | Simultaneous outer and inner diameter control | |
| Inner weld bead | Max. 0.15 mm — proprietary Delmàs process control | |
| Material | E195 and E235 (standard), E355, micro-alloyed steels and the full range of carbon steel | |
| Outer surface finish | Bright, calibrated. Available with or without heat treatment as required. | |
| Inner surface finish | Controlled bore, minimised bead | |
| Wall thickness | 0.40 mm – 2.00 mm | |
| OD/ID tolerances | Exact per standard or order — defined jointly with the client | |
| Standards | EN 10305-3 · EN 10305-2 (hybrid) · ASTM 513 Type 4 · SAE J356 | |
| Supply formats | Standard length · Coil · Cut-to-length · Finished part | |
| Portfolio position | 56% of combined OPTIM + PREMIUM volume — Delmàs's most in-demand range | |
| Standard | Market | What it defines for OPTIM |
|---|---|---|
| EN 10305-3 | Europe | Precision steel tubing with calibrated outer diameter. The OPTIM range meets the OD control requirements of this standard. Applies in applications where outer fit is important. |
| EN 10305-2 | Europe | Precision steel tubing with calibrated bore. The OPTIM range incorporates inner weld bead control without reaching the mirror-bore level of the PRECISE range. Defines the inner performance of the product. |
| ASTM 513 Type 4 | USA/Global | ERW tubing with tighter dimensional tolerances. Type 4 includes greater dimensional control, making it the closest American equivalent to the OPTIM range control level. Required in projects with North American homologation. |
| SAE J356 | Automotive | SAE standard for precision welded steel tubing. Required by American OEMs and their global Tier 1 suppliers for seat components, mechanisms and low-pressure circuits. |
The product certificate is issued with every delivery and includes steel composition, mechanical properties of the batch, verified dimensions and inner bead measurement (max. 0.15 mm). It is not an additional document: it is our standard delivery.
| Parameter | PREMIUM | OPTIM ★ Exclusive | PRECISE |
|---|---|---|---|
| Outer Ø control | ✔ High precision | ✔ High precision | ✔ High precision |
| Inner Ø control | ✗ Not applicable | ✔ High precision | ✔ Maximum precision |
| Inner bead control | ✗ Not applicable | ✔ Max. ≤ 0.15 mm | ✔ Mirror bore |
| Outer finish | ✔ Bright/chrome plating | ✔ Bright, calibrated | — Standard |
| Available diameter | 3–13 mm | 3–10 mm | 8–25 mm |
| Primary standard | EN 10305-3 | EN 10305-3/2 | EN 10305-2 |
| Ideal application | Chrome finishes, exterior styling | Axles, wheels, brakes, seats, mechanisms | Gas springs, hydraulics, pistons |
| Cost-to-performance ratio | High (outer only) | Optimal (outer+inner) | High (maximum interior) |
The three Delmàs ranges are not versions of the same product at different quality levels. They are technical solutions for different technical problems. The right range depends on which dimension is critical to your application.
Four formats, one especially relevant for OPTIM.
The OPTIM range is available in the same four supply formats as the rest of the Delmàs portfolio. The coil format is especially relevant for this range, as most of its applications (industrial wheels, seat mechanisms, brake cable terminals) are manufactured on automated continuous-feed lines.
Standard length
Standard-length bars for conventional cutting and machining processes at the client's plant.
Coil ⭐
Continuous coil. For automated axle, wheel and terminal lines. Reduces scrap 10–15% vs bar. Recommended for CNC feed lines without prior cutting.
Cut-to-length
Exact length with tight tolerance. Eliminates cutting at the client's plant, the associated scrap and the logistics of offcuts.
Finished part
OPTIM tube as the base for a transformed part: cutting, bending, punching. Ready to assemble.
Why ≤ 0.15 mm changes the process.
Standard market tubing
- Uncontrolled inner bead (up to 0.5 mm)
- Friction and unevenness in the finished product fit
- Noise and misalignment resulting in a lower-quality product
- Rejects during production. Lost time, broken tools, wasted product.
- Variable clearances between batches: inconsistencies in production and assembly
- Quality control rejects at the end customer
OPTIM Range · Bead ≤ 0.15 mm
- Precise fit and optimal surface finish — the real strength is complete dimensional fit
- Controlled inner bead: max. 0.15 mm
- Perfect product fit. Consistent in-process behaviour.
- Higher-quality end product, greater customer value.
- No production issues. Longer tool life, higher process productivity.
- Batch-to-batch dimensional consistency: predictable assembly
- Zero dimensional rejects on the final product.
Where the OPTIM range changes the rules of the process.
Hospital and logistics industrial wheels · Vehicle seat mechanisms · Self-service trolleys · Rotating displays · Wheelchairs.
Garage door closure mechanisms · Panic-safe security doors · Lock cylinders · Perimeter closure systems.
Wheel-axle manufacturing lines · Seat mechanisms in coil · Brake cable terminals · Transfer lines for interior mechanisms.
Dimensional control that no other tube on the market can offer.
The OPTIM range is the solution for any industrial application where a precise fit between the tube inner diameter and any axle, tool or component is critical to the performance of the finished product.
In Mobility, OPTIM is the reference solution across every subsector where the tube inner diameter is critical for functionality. The controlled bead (≤ 0.15 mm) and the custom-exact inner diameter guarantee a perfect fit of the tube in its application.
OPTIM's simultaneous OD+ID control guarantees a precise fit in automotive mechanisms where OEMs allow no dimensional variation. Coil supply feeds automated lines directly.
In the home sector, OPTIM tubing provides the precise fit and surface quality that design and domestic-use products demand, with the option of decorative profiles or finishes directly from the factory.
In engineering, the OPTIM range solves applications where the tube is an active part of a functional mechanism. OD+ID control ensures the fit that mechanical, electrical, hydraulic and closure systems require.
We manufacture the part your product needs.
At Delmàs we do not limit ourselves to manufacturing round tubing in standard lengths. As manufacturers with our own transformation capability, we can deliver a complete solution — from raw material to finished part ready to assemble.
Special profiles
Square, oval or special-geometry tubing. We manufacture non-round profiles from our precision welding process while maintaining the same OD+ID control that characterises the OPTIM range.
Decorative finishes
Integrated decorative elements. Silk-screening, engravings, textures and marks incorporated directly during manufacturing, with no additional operations at the client's plant.
Transformation
Cut-to-exact-length, controlled-radius bending, hole punching and end tapering. We reduce operations and suppliers in your chain.
Finished part
From OPTIM tube to finished part: we deliver the component with bright surface and full dimensional control, ready for the galvanic bath or direct assembly.
As manufacturers, our commitment does not end when the tube leaves the welding machine: it ends when the part we deliver fits perfectly into your product.
Manufacturers that cannot afford a single fit failure.
The OPTIM range is behind the products most seen and most used in industrial and everyday life: the trolleys that roll without squeaking, the seats that slide in silence, the mechanisms that open and close thousands of times without wearing out.
Bring us a challenge and we solve it together.
We don't just manufacture tubes; we develop tailored solutions for critical applications. Send us the diameter, the wall thickness and the application. We will analyse the technical feasibility and, if needed, manufacture samples for final validation.
- Technical response within 24 hours
- Non-standard diameters and wall thicknesses available
- Physical samples in your exact specification