If your part is sheet metal, laser cutting is usually faster and cheaper than waterjet. Waterjet earns its place when heat is a problem, the plate is very thick, or the material isn't metal at all: glass, stone, tile, rubber, or composites.
That's the honest summary, and it means most mild steel, stainless, and aluminium parts under a few millimetres never need to go near a waterjet. The interesting cases are the exceptions, like a part that can't tolerate any heat-affected zone, or a mixed job with a stainless plate and a rubber gasket. Here's how the two processes work, how they compare, and how to tell which one your job needs.
How waterjet cutting works
A waterjet pumps water to extremely high pressure and forces it through a tiny orifice, creating a thin, fast stream. For metal, a fine abrasive, usually garnet, is fed into that stream. The abrasive particles do the cutting by eroding the material away.
The key point is that it's a cold process. There's no melting, so there's no heat-affected zone, no oxide on the edge, and no thermal distortion. Pure water without abrasive is used for soft materials like foam and rubber.
A laser, by contrast, cuts by melting. A focused beam heats a tiny spot and an assist gas blows the melt out. It's very fast on thin metal, but it's a thermal process, so there's always a narrow heated zone along the edge. If you want the full picture, our post on what laser cutting is covers it.
Side-by-side comparison
| Laser cutting | Abrasive waterjet | |
|---|---|---|
| How it cuts | Melts with a focused beam | Erodes with water and abrasive |
| Heat-affected zone | Small, but present | None |
| Speed on thin sheet | Fast | Much slower |
| Cost on thin sheet metal | Usually lower | Usually higher |
| Very thick plate | Slows down and gets expensive | Handles it, slowly |
| Materials | Metals in a sheet metal shop (plus some non-metals on CO2 lasers) | Almost anything: metal, glass, stone, tile, rubber, composites |
| Kerf | Narrow, about 0.1–0.3 mm | Wider |
| Edge | Smooth on sheet; oxide on oxygen-cut mild steel | Matte, oxide-free; can taper on thick material |
| Mess | Fume and spatter | Wet abrasive sludge |
Heat: the real deciding factor
Most of the time, the laser's heat-affected zone simply doesn't matter. It's narrow, and on sheet metal parts that will be bent, welded, or powder coated, nobody will ever notice it.
It does matter in a few situations:
- Hardened or heat-treated material, where heating the edge changes its properties.
- Very fine, heat-sensitive features, like a thin web between closely spaced holes, which can warp in thicker material.
- Specifications that rule out thermal cutting, which some engineering drawings state outright.
In those cases waterjet is the safer choice. If none of them apply, the heat argument is mostly theoretical.
Materials laser can't touch
This is the other big reason to choose waterjet. A laser in a sheet metal shop is set up for metal. Glass, stone, ceramic tile, and thick rubber are either impossible or impractical to laser cut, but a waterjet goes through them happily.
So if your job mixes materials, say stainless brackets with matching rubber gaskets, or a steel frame with a stone insert, it's normal to laser cut the metal and waterjet the rest.
Very thick metal plate is the other area where waterjet comes into its own. A laser slows down a lot as plate gets heavier, and at some point it stops being practical. A waterjet keeps going, slowly, through plate far thicker than most sheet metal shops would put on a laser. If the part also needs to stay free of heat, that combination points firmly to waterjet. If it doesn't, plasma is often the cheaper route for heavy plate.
Speed, accuracy, and cost on sheet metal
On thin and medium sheet, a laser is much quicker. Abrasive waterjet erodes rather than melts, so it moves slower, and it uses abrasive the whole time it's cutting. Slower cutting plus consumables usually means a higher price for the same part.
Accuracy is good on both, but the edges differ. Laser-cut features on thin sheet are commonly quoted around ±0.1 mm in the industry. A waterjet stream loses energy as it goes deeper, so on thicker material the cut can taper slightly, with the bottom narrower than the top. Modern machines tilt the head to correct for that. On thin sheet, either process is accurate enough for most work. Our guide to laser cutting tolerances explains what affects the final size of a laser-cut part.
The edge finish looks different too. A waterjet edge has a fine, matte texture with no oxide. A laser edge on stainless or aluminium cut with nitrogen is smooth and bright. On mild steel cut with oxygen, the laser leaves a thin oxide layer that's usually cleaned off before powder coating.
Which one should you pick?
Run through these questions:
- Is the material metal? If not, it's waterjet.
- Does the drawing or the application rule out heat? If yes, waterjet.
- Is the plate very thick, beyond what laser shops usually cut? Waterjet or plasma, depending on accuracy needed. See our laser cutting vs plasma cutting comparison.
- Is it sheet metal that will be bent, welded, or coated? Laser, almost always.
Getting your sheet metal part cut
Our laser cutting service handles mild steel, stainless steel, aluminium, and 3CR12, and the parts can go straight on to bending, fabrication, and powder coating on the same order.
If you're not sure whether your part needs special treatment because of heat, say so on the quote and explain what the part does. Send the drawing with the material, thickness, and quantity, and start a quote for laser cutting.