Picking the wrong cutting process is one of the fastest ways to waste money in a metal shop. You either pay for edge quality you do not need, or you save on cutting and then spend more on grinding and rework. This guide shows you how to match the four common methods, laser, plasma, waterjet, and mechanical shearing, to your actual part, so you order the right process the first time.
The four methods and what each one really does
Every cutting method removes material in a different way, and that difference decides edge quality, tolerance, and heat damage.
Laser cutting
A focused beam melts and blows away a narrow line of metal. It gives clean, square edges and tight tolerances, typically well under half a millimeter on thin sheet. It shines on carbon steel, stainless, and aluminum up to roughly 20 to 25 mm depending on machine power. Above that, cut speed drops and cost climbs fast.
Plasma cutting
An ionized gas jet melts the metal. It is fast and cheap on thicker conductive plate, from a few millimeters up to 40 mm and beyond. The trade off is a wider kerf, a small bevel on the edge, and a heat affected zone. Good for structural steel, brackets, and parts that get welded or machined afterward.
Waterjet cutting
A high pressure stream of water and abrasive erodes the material. There is no heat, so no warping, no hardened edge, and no change to the metal near the cut. It handles very thick plate, stainless, titanium, aluminum, and even stone or composites. It is slower and the running cost is higher because of abrasive consumption.
Mechanical shearing and punching
A blade or die separates the metal by force. It is extremely cheap and fast for straight lines and simple holes in thin sheet, but it cannot do complex contours and it leaves a burr and slight edge deformation.
How to choose: match the method to the part
| Priority | Best choice | Why |
| Tight tolerance, thin sheet | Laser | Narrow kerf, square clean edge |
| Thick structural plate, low cost | Plasma | Fast on thick conductive metal |
| No heat, thick or exotic metal | Waterjet | No heat affected zone or warping |
| Simple straight cuts, high volume | Shearing | Cheapest per part on thin sheet |
A real example
A customer needed 300 stainless steel mounting plates, 6 mm thick, with a mirror bracket profile and holes that had to line up on assembly. They first asked for plasma to save money. The problem: the heat affected zone would discolor the stainless near the edge, and the hole position tolerance was too loose for their fixture. We moved the job to laser. The edge stayed clean enough to skip deburring on the visible face, holes landed within tolerance, and total cost, including the rework they avoided, came out lower than the plasma quote.
Common mistakes and how to fix them
Choosing only on cutting price. Plasma may quote cheaper, but if the part then needs grinding, straightening, or a second setup, the finished cost is higher. Compare total cost to a finished part, not the cut alone.
Ignoring the heat affected zone. On stainless, tool steel, or parts that get heat treated later, thermal cutting changes the metal near the edge. If that matters, choose waterjet.
Forgetting kerf width in the drawing. Plasma removes a wider strip than laser. If your holes or slots are dimensioned to the wrong kerf, they end up oversized. Tell your shop the process before finalizing critical dimensions.
Over specifying tolerance. Asking for laser precision on a rough weld bracket just raises cost. Match the process to the function.
Action checklist before you order cutting
- Confirm material type and thickness.
- Decide the tightest tolerance the part actually needs, not the tightest you can imagine.
- Ask whether the edge is visible or hidden, and whether it gets welded or machined later.
- Check if the metal is heat sensitive or gets heat treated afterward.
- Compare quotes as finished parts, including deburring and any straightening.
- Tell the shop the process early so kerf is accounted for in the drawing.
Conclusion and next step
There is no single best cutting method, only the best fit for a given part. Start from the function, the material, and the tolerance, then let those decide the process. As a next step, take one part you order regularly and re run the comparison table above; you may find you are paying for precision you do not use, or losing money on rework you could avoid.
FAQ
Is laser always more accurate than plasma?
On thin to medium sheet, yes, laser gives a narrower kerf and tighter tolerance. On very thick plate the gap narrows and plasma may be the practical choice on cost.
When is waterjet worth the higher cost?
When heat would ruin the part: heat treated steels, stainless where discoloration matters, titanium, or very thick sections where warping is a risk.
Can one method cover everything?
No shop realistically runs one process for all work. Most combine plasma or laser for profiles with shearing and punching for simple high volume parts.
Why does my cut part have a slanted edge?
That bevel is normal on plasma and on thick laser cuts. If you need a square edge, specify it, and expect either a slower cut or a secondary machining step.
Does thicker material always cost more to cut?
Generally yes, because cut speed drops with thickness. The increase is steepest on laser, which is why thick plate often moves to plasma or waterjet.
