What thickness and types of metal can be cut with industrial laser cutting machines?
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- Issue Time
- Jul 10,2026
The short answer
Industrial fiber laser cutting handles roughly 0.5 to 20 mm across common metals: about 20 mm carbon steel, 15 mm stainless and 12 mm aluminium on a 6 kW machine, rising to 60, 40 and 30 mm at 20 kW. Copper and brass stay under 10 mm.
Thickness is set by power, and power alone does not promise a clean cut
Every laser cutting capacity table is really two numbers, not one. The first is the maximum thickness a given power can penetrate, which is a physical limit set by how much energy the beam can deposit into the kerf before the molten metal stops clearing. The second is the range in which the machine cuts cleanly at a production rate the shop can actually bill for, which is always narrower. A 6 kW fiber laser will pierce 25 mm carbon steel, but it will not cut a hundred of those parts in a day at an edge quality anyone would accept. When a supplier quotes a maximum thickness, ask for the speed and the edge roughness that came with it, because both are part of the answer.
The practical consequence for a buyer is to specify thickness against a machine class rather than a single figure. Thin-sheet work from 0.5 to 6 mm is comfortable on most modern fiber machines and is where the technology is clearly superior to plasma and punching on edge quality. Medium plate from 6 to 20 mm is the ordinary production band. Above 20 mm the field narrows to high-power machines, cutting speed falls sharply, and the comparison with plasma or a machining operation has to be made on total cost rather than on the cut alone.
What each metal can take at a given power
Materials do not behave alike in the beam, and the differences are large enough to change the machine you need. Carbon steel is the easiest: oxygen assist adds exothermic heat and roughly doubles the usable thickness at the same power. Stainless steel has a much lower thermal conductivity and a chromium-oxide surface that has to be cut with high-pressure nitrogen to leave an oxide-free edge, so it lands somewhere between carbon steel and aluminium on thickness. Aluminium reflects a substantial share of the beam at the fiber wavelength and conducts heat away fast, so it needs roughly 30 to 40 percent more power than carbon steel for the same thickness, and its practical ceiling sits below stainless. Copper and brass reflect even more strongly and are the hardest of the group, needing very high power and careful pierce control to avoid back-reflection damage to the optics.
Power against thickness
The relationship between laser power and usable carbon steel thickness is steep but not linear, and the useful way to read it is as a ladder rather than a formula. A 1.5 kW machine manages single-digit thicknesses; 3 kW reaches the low teens; 6 kW takes the metal into the 25 mm band and is where most job shops settle; 12 kW and 20 kW extend the ceiling to 40 and 60 mm but only make commercial sense on work that genuinely needs thick plate. Each step up in power costs far more than the previous one, and the thick end of every machine's range is cut slowly, which is why the honest quote is always based on the thickness the shop actually runs rather than the one in the brochure.
The gas choice changes the edge and the price
Assist gas is the lever buyers most often overlook, and it moves both the edge and the bill. Oxygen reacts with carbon steel and adds heat, which lets the beam cut thicker material faster, but it leaves an oxide edge that is usually acceptable only where the part will be painted or cleaned before welding. Nitrogen is inert and produces a clean, bright, weld-ready edge on stainless and aluminium, but it has to be supplied at high purity and pressure, and gas consumption on a nitrogen-heavy programme can be a visible line in the quote. Compressed air sits between the two on cost and finish and works well on thinner carbon steel where the edge requirement is modest. Compressed air on thin sheet is often the cheapest clean cut, while nitrogen on thick stainless is often the most expensive part of the job.
Gas purity matters as much as gas type. Shop air at roughly 80 percent nitrogen leaves an oxide film; oxygen at 99.5 percent purity is enough for carbon steel; nitrogen wants 99.99 percent to keep stainless bright. Where a shop runs nitrogen for several shifts a day, an on-site generator usually pays back within a year or two against bottled gas, which is why two quotes for the same part can differ once the gas strategy differs.
Material behaviour that limits the cut
Beyond thickness and power, five material effects decide whether a cut is trouble-free or marginal. Reflectivity matters most on copper and brass, where back-reflection at the fiber wavelength can damage the optics unless power, focus and pierce sequence are managed. Surface condition, meaning mill scale, rust, oil and coatings, changes how efficiently the beam couples to the surface, so a change of sheet supplier can move the result without anything else changing. Thermal load is the reason small, closely nested parts distort while large ones do not, because heat accumulates faster than the thin section can dissipate it. Kerf taper appears on thick plate as the beam diverges through the depth, giving a narrower exit than entry and a wall that is not quite parallel. And dross on the underside of thick carbon steel is the visible sign that gas pressure and speed are not matched to the section.
Where laser cutting is the wrong tool
Four situations sit outside what a laser does well, and naming them early saves a quote. Copper and brass thicker than about 10 mm usually move to waterjet or a different machine class, because the reflectivity risk and the power required rarely justify laser. Very thick plate above the machine's clean band is better cut by plasma on cost or by waterjet where the edge must have no heat-affected zone. Materials that are coated, laminated or sensitive to heat can lose their surface at the cut edge, so a cold process is safer. And parts that need a deep, machined feature or a tapped hole are a fabrication and machining combination rather than a pure cutting job. The laser is unbeatable at flat, thin and mid-thickness profiles; it is not the answer to every metal shape.
Two further limits are worth stating. A hole cannot be cut smaller than the kerf, and in practice the working minimum for a clean round hole runs around one times the material thickness. And a laser-cut tolerance is the tolerance of the blank, not of the finished part, so a bent or welded assembly inherits forming and welding error on top of the cut error.
How to specify a laser-cut part
Five items let a supplier quote on the right machine and the right gas. Give the material grade and the actual decimal thickness rather than the gauge name, because the two do not always match. State the thickest section in the part, since that is what sets the machine and the price. Say which edge condition matters, whether an oxygen cut with a grey edge is acceptable or the part needs a nitrogen cut to weld or passivate. Name the tolerance on the profile separately from the tolerance on any formed or assembled feature. And give the quantity and the nesting expectation if you have a flat pattern, because material yield changes the price as much as machine time does.
See sheet metal fabrication for how cutting sits in the wider process route, laser cutting for the cutting service itself, and surface finishing for what happens to the cut edge afterwards.
Scope and sources. The power-to-thickness ladder for carbon steel, stainless and aluminium, the practical ceilings of about 60 mm carbon steel, 40 mm stainless and 30 mm aluminium at 20 kW, the requirement of 18 to 22 bar nitrogen for stainless, the edge effect of oxygen, air and nitrogen, the note that shop air is about 80 percent nitrogen and leaves an oxide film, the kerf taper figures on 20, 40 and 60 mm plate, the heat-affected zone of about 0.4 mm on 25 mm steel cut with oxygen, and the laser-cut limitations of reflectivity, thick-plate edge roughness, kerf width on micro parts and high-pressure gas cost come from a fiber laser thickness reference (1.5 kW for 6 to 10 mm carbon steel, 4 to 6 mm stainless and 3 to 5 mm aluminium; 3 kW for 10 to 15, 6 to 10 and 5 to 8 mm; 6 kW for 20 to 30, 12 to 20 and 8 to 12 mm; 12 kW for 30 to 40, 20 to 30 and 12 to 20 mm; 20 kW for 40 to 60, 30 to 40 and 20 to 30 mm; and the guidance that the beam must be centred because a 0.2 mm drift costs cut depth on thick plate). The power bands for 3 kW, 6 kW, 8 kW and 12 kW machines, the note that stainless needs about 25 percent more power density than carbon steel and aluminium about 30 to 40 percent more, that copper needs very high power beyond about 10 mm, the material tolerance bands of 0.05 to 0.15 mm on carbon steel, 0.07 to 0.18 mm on stainless, 0.10 to 0.25 mm on aluminium and 0.15 to 0.30 mm on copper, and the minimum hole diameter of about one times material thickness come from a laser cutting thickness and tolerance guide and a fiber laser capacity review (3,000 W for 16 to 18 mm carbon steel, 12 to 14 mm stainless and 10 to 12 mm aluminium; 6,000 W for 25 to 30, 20 to 22 and 18 to 20 mm; 12,000 W for 35 to 40 mm and above, 30 to 35 and 25 to 28 mm, with maximum versus ideal ranges distinguished and the note that results vary with material grade, gas purity and system quality). The material-specific thickness ceilings by laser power class come from a fiber laser capacity guide (500 W for about 6 mm carbon steel, 3 mm stainless and 2 mm aluminium; 1,000 W for 10 to 12, 5 and 3 mm; 6,000 W for about 25 mm carbon steel, 20 mm stainless, 16 mm aluminium and 12 mm copper; 10,000 W and above reaching 40 to 50 mm stainless and 40 mm aluminium, with carbon steel easier because of its composition and aluminium and copper limited by their low absorption). These are planning ranges for a well-maintained machine, not a warranty on any particular cut.