How thick can a water jet cut?

Most machines cut steel up to about 150–200 mm (5.91–7.87 inch), but speed drops sharply with thickness. Up to about 50 mm (1.97 inch) in steel and more in softer materials is everyday work.

Does water jet cutting harden or burn the edge?

No. It is a cold process, so there is no heat-affected zone, no hardening and no change in the material next to the cut.

Is water jet cutting accurate enough for finished parts?

For many parts, yes, at about ±0.1–0.2 mm (±0.0039–0.0079 inch). Close-tolerance holes and fits are usually cut slightly under size and finished by machining.

Water jet cutting job work: thickness, accuracy, uses

Water jet cutting cuts profiles with a very thin, very high-pressure stream of water mixed with fine garnet sand. It cuts almost any material, including thick steel, stone, glass, rubber and plastics, without heat, so there is no burnt edge and no hardening. It is slower and costlier than laser on thin steel, but often the only clean way to cut thick or heat-sensitive material.

Quick facts

Pressure: About 3,500–6,000 bar
Cuts: Metals, stone, glass, rubber, plastics, composites, foam
Thickness: Up to about 150–200 mm (5.91–7.87 inch) in steel; slow beyond about 50 mm (1.97 inch)
Typical accuracy: About ±0.1–0.2 mm (±0.0039–0.0079 inch)
Heat-affected zone: None (cold cut)
Usually priced: Per metre of cut, by material and thickness

How it is done

A pump pressurises water to several thousand bar
Garnet abrasive is mixed into the jet in the cutting head (pure water only for rubber, foam and food)
The CNC table moves the head along the profile from a DXF drawing
The jet cuts through and loses energy in a water tank under the part
Edges show a slight taper and fine striations; slower cutting gives a better edge

Water jet, laser or plasma?

	Water jet	Fibre laser	Plasma
Materials	Almost anything	Metals (some plastics, wood)	Conductive metals only
Thick steel	Yes, slowly	Up to about 25–30 mm (0.984–1.18 inch) typical	Yes, faster, rougher
Heat effect	None	Small	Larger
Thin sheet speed	Slow	Very fast	Fast

What to send the cutter

DXF or DWG of the profile at 1:1 scale
Material, grade and thickness
Quantity and sheet or plate size if you supply the material
Edge quality needed (rough, standard or fine)
Tolerance on critical sizes and holes
Whether the parts must stay free of rust (dry quickly after cutting)

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Related job work

Machines

Materials

Questions

How thick can a water jet cut?: Most machines cut steel up to about 150–200 mm (5.91–7.87 inch), but speed drops sharply with thickness. Up to about 50 mm (1.97 inch) in steel and more in softer materials is everyday work.
Does water jet cutting harden or burn the edge?: No. It is a cold process, so there is no heat-affected zone, no hardening and no change in the material next to the cut.
Is water jet cutting accurate enough for finished parts?: For many parts, yes, at about ±0.1–0.2 mm (±0.0039–0.0079 inch). Close-tolerance holes and fits are usually cut slightly under size and finished by machining.

The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 18 October 2026.