Carbon Fiber Tube - 25mm x 23mm x 1000mm: Custom Size Sourcing

Introduction

A carbon fiber tube - 25mm x 23mm x 1000mm is one of the most requested custom sections in robotics, marine and industrial automation: a 25 millimetre outer diameter with a 23 millimetre bore leaves a 1 millimetre wall, which is thin for a large tube but behaves very differently from the 1-2 millimetre walls on 8 or 10 millimetre stock rod. Buyers search for this exact size because it drops into existing 25 millimetre fixtures and pneumatic cylinder envelopes while carrying four to six times the bending stiffness of a conventional 25 × 17 millimetre thin-wall tube. This article covers how the section is actually made, what tolerances to demand at one metre length, and how to price a carbon fiber tube 23mm-bore order without paying custom-engineering rates for a standard layup.

The specification sounds simple — round, 1000 millimetres long, inside diameter 23 millimetres — but wall thickness of 1 millimetre pushes the section into thick-walled territory where layup sequence and curing pressure dominate the result, and where pultrusion and roll-wrapping diverge sharply in both cost and performance.

Why 25mm OD / 23mm ID Is a Distinct Section, Not Just a Thin Tube

At 25 millimetres outside and 23 millimetres inside, the wall-to-diameter ratio is 4 percent — thin enough to look like a standard tube, thick enough that the laminate schedule cannot be a single-ply afterthought. The numbers that matter for a carbon fiber tube thick walled like this:

• Bending stiffness: second moment of area for the annulus is about 6.6 cm⁴; with a quasi-isotropic layup at 50 GPa effective modulus that gives roughly 330 N·m of flexural rigidity — approximately 4.5 times a 25 × 21 millimetre double-wall tube of the same length.
• Mass: at 1.55 g/cm³ density the tube weighs about 360 grams per metre; a same-size aluminium tube weighs about 1,030 grams, so the carbon section delivers the stiffness at a third of the mass.
• Hoop behaviour: 1 millimetre of wall on a 25 millimetre bore is thin for internal pressure — this section suits structural bending, not pressure vessels, and any press-fit insert needs an internal sleeve to spread the radial load.
• Surface for bonding: the 23 millimetre bore is large enough to accept a bonded end cap or a machined aluminium plug with 30-40 millimetres of bond length, which is what makes the section usable as a robotic arm segment.

Designers reach for this size precisely because it sits between the flimsy 25 × 21 double-wall tube and the heavy 25 × 19 thick-wall section, holding the stiffness target without the mass penalty.

Manufacturing a Carbon Fiber Tube 25mm x 23mm: Roll-Wrapped Versus Pultruded

Two processes can deliver a carbon fiber tube 25mm × 23mm, and they are not interchangeable for precision work. Roll-wrapping dominates at this wall thickness: prepreg plies are wrapped around a polished mandrel, bagged and cured under vacuum or autoclave pressure, then pulled off the mandrel — which is how the 23 millimetre bore tolerance is held. Pultrusion can reach the outer diameter but struggles to control the inner bore, because the fiber pack is pulled through a heated die sized for the outside surface; at 1 millimetre wall, bore variation of ±0.15 millimetres is common.

Attribute	Roll-wrapped (recommended)	Pultruded
Bore tolerance (23 mm target)	±0.05 mm	±0.15 mm
Outer diameter tolerance	±0.1 mm	±0.05 mm
Straightness over 1000 mm	0.2-0.5 mm	0.5-1.0 mm
Layup control	Full quasi-isotropic options	Unidirectional dominant
Typical unit price, 1000 mm	55-95 USD	25-45 USD
Best for	Robotics arms, test fixtures	General bracing, low-load booms

For anything that must slide into a 25 millimetre bearing or collet, the roll-wrapped bore tolerance is the deciding factor; the pultruded tube is the right call only when the 23 millimetre dimension is nominal and the load is modest.

Ordering a Carbon Fiber Tube - 25mm x 23mm x 1000mm: Length, Ends and Tolerances

When you order a carbon fiber tubes and rods program that includes this section, write the tolerance into the purchase order rather than accepting "standard":

• Length: 1000 millimetres cut square to ±1 mm; specify whether the ends will be machined afterwards, because cut-off sanding opens the wall by 0.1-0.2 millimetres per face.
• Bore: 23 millimetres +0.05/-0.00 for slip fits; if the tube receives a bonded insert, relax to +0.15 and let the adhesive fill.
• Straightness: 0.3 millimetres over the full metre for arm segments; 1 millimetre acceptable for non-critical bracing.
• Surface: sanded outer finish ready for bonding or gloss finish for cosmetic use — state which, because the mandrel side of a roll-wrapped tube is glossy and the bag side is matte.
• Certificates: fibre grade (T300 or T700), resin Tg, and a dimensional inspection report for the first article.

Lead time from a stocked manufacturer for this size is typically 3-5 weeks for roll-wrapped tube and 1-2 weeks for pultruded; add a week for machined ends. Minimum order quantities are usually one to five pieces for roll-wrapped custom sizes — this is not a container-load section — which is why the unit price looks high next to catalogue pultruded tube.

Frequently Asked Questions

Is a 1 millimetre wall on a 25mm carbon fiber tube too thin for structural use?

Not for bending-dominated structures. The section has a second moment of area near 6.6 cm⁴, which at a 50 GPa quasi-isotropic modulus gives about 330 N·m of rigidity — four to six times a standard thin-wall tube. What it cannot do is carry internal pressure or point crush loads without an internal sleeve or a bonded insert spreading the force.

Can a pultruded tube meet a 23mm bore tolerance?

Only loosely. Pultrusion controls the outer diameter well but the bore wanders by ±0.15 millimetres or more because it is formed against the die, not a mandrel. If the tube must slip into a 23 millimetre bearing, specify roll-wrapped construction with a ±0.05 millimetre bore tolerance instead.

What is the price difference between pultruded and roll-wrapped at 1000 millimetres?

Expect 25-45 USD for a pultruded 25 × 23 × 1000 millimetre tube and 55-95 USD for roll-wrapped, depending on fibre grade and order quantity. The roll-wrapped premium buys bore tolerance, layup control and straightness — the three attributes that decide whether a robotic arm segment performs or binds.

Conclusion

The carbon fiber tube - 25mm x 23mm x 1000mm earns its place as a standard custom section because it delivers thin-wall mass (about 360 grams per metre) with near thick-wall stiffness (roughly 330 N·m), provided you specify roll-wrapped construction with a held bore. Write the tolerances into the purchase order — ±0.05 millimetre bore, 0.3 millimetre straightness, square ends — and demand a first-article inspection report before the batch. For this exact section and neighbouring custom sizes, browse our carbon fiber tube range or contact our technical team with your drawing, load case and annual volume.