Capability Explainer
What Is Waterjet Cutting and What Can It Cut?
Waterjet cutting uses a high-pressure stream of water mixed with abrasive garnet particles to cut through metal without heat. Because there is no heat-affected zone, waterjet is the preferred process for materials that warp, harden, or lose temper under laser or plasma heat: thick aluminum, hardened steel, titanium, and non-metals like rubber and composites. Cut width is typically 0.030 to 0.040 inches and tolerances are comparable to laser cutting on most materials and thicknesses.
How Waterjet Cutting Works
A waterjet system pressurizes water to between 40,000 and 90,000 PSI and forces it through a small orifice, typically 0.010 to 0.015 inches in diameter. For cutting metal, abrasive garnet is mixed into the stream just before the nozzle. The garnet particles do the actual cutting; the water accelerates them and carries away kerf waste. The stream exits at roughly three times the speed of sound.
The cutting head moves on a CNC-controlled gantry, following a programmed tool path from a DXF file, exactly as a laser or plasma cutter does. Work is placed over a tank of water that dampens noise and captures debris. Because the energy is mechanical rather than thermal, no melting occurs at the cut edge and the material grain structure, hardness, and temper remain unchanged at the cut face.
What Materials Can Waterjet Cut?
- Mild steel (A36, A572): any thickness from thin sheet to 6-inch-plus plate; preferred over laser on thick plate
- Stainless steel (304, 316, 316L): cuts without edge hardening or heat discoloration; useful for food-grade parts where a clean unoxidized edge is required
- Aluminum (6061, 5052, 3003): no edge melting or warping; handles thick plate cleanly where laser reflectivity is an issue
- Titanium: avoids the oxidation issues that arise with plasma or laser cutting
- Hardened plate (AR400, A514): abrasive waterjet cuts pre-hardened material without changing its hardness at the cut face
- Copper and brass: highly reflective materials that create process issues for fiber laser systems pose no problem for waterjet
- Non-metals (rubber, gasket material, HDPE, composites): waterjet cuts these precisely without fraying, melting, or edge contamination
Waterjet Cutting Tolerances
On typical steel and aluminum parts at moderate thickness, waterjet holds positional tolerances of approximately plus or minus 0.005 to 0.010 inches. At very thick material (3-inch-plus steel), the jet can taper slightly at the bottom of the cut; this is corrected using a tilting cutting head on machines equipped for that. The laser cutting vs waterjet comparison covers process tradeoffs and tolerance comparisons in full detail.
Waterjet vs Laser Cutting: Key Differences
| Factor | Waterjet | Fiber Laser |
|---|---|---|
| Heat-affected zone | None | Narrow HAZ; edge hardening possible on some alloys |
| Material range | Very wide: metals, composites, non-metals | Metals primarily; limited on highly reflective materials |
| Thick plate (over 1 inch steel) | Handles well; slower but clean | Quality degrades above about 1 inch on most machines |
| Thin sheet (under 1/4 inch) | Works but slower | Faster; preferred for production sheet work |
| Edge finish | Matte; no edge hardening or oxide | Smooth; stainless may show heat discoloration |
| Consumable cost | Abrasive garnet adds per-hour cost | Lower consumable cost on most materials |
| Non-metal cutting | Yes: rubber, plastic, composites | No |
For production runs of thin to mid-gauge steel parts, laser is almost always faster and more cost-effective. For thick plate, heat-sensitive alloys, hardened materials, or oxide-free stainless edges, waterjet is the better choice.
What Waterjet Cannot Do
Waterjet does not drill holes through tube or structural sections from the side. The process requires flat surface access from above. For tube and structural shapes, tube laser cutting handles mitered ends, saddle cuts, and holes. Waterjet also does not bend or form parts. Flat blanks go to the press brake or plate rolling station for any forming required. Precision bores and tight-cylindricity holes require CNC milling after cutting; see the vertical mill service.
Surface Finish After Waterjet Cutting
Waterjet-cut edges have a characteristic matte, slightly textured surface from the abrasive action. On structural parts this surface goes directly to welding or forming. Stainless steel parts cut by waterjet show none of the blue-black oxide that laser or plasma cutting produces, which matters for food-grade, pharmaceutical, and aesthetic applications. After cutting, waterjet blanks follow the same downstream path as laser-cut parts: forming, welding, and finishing. Paragon handles all of these steps under one roof. Review the full services overview.
Common Waterjet Applications at a Job Shop
- Thick plate parts (over 3/4 inch) in steel, aluminum, or stainless where laser quality is marginal
- Hardened or abrasion-resistant plate (AR400, A514) where cut hardness must be preserved
- Titanium and exotic alloys where thermal oxidation must be avoided
- Copper, brass, and high-reflectivity metals that cause issues on fiber laser systems
- Gaskets, rubber pads, and non-metal components nested alongside metal parts in a project
- Stainless steel parts where an oxide-free edge is required before welding
Tip: You do not need to specify the cutting process on most prints. A capable fabricator selects the best process for the material and geometry. If a specific edge requirement (no HAZ, oxide-free, hardness-preserved) must be met, call it out as a surface or edge quality note rather than mandating a specific process. The RFQ checklist covers what information a fabricator needs to quote accurately.
Frequently Asked Questions
What is the difference between waterjet cutting and laser cutting for metal?
The core difference is heat. Laser cutting melts material along the cut path, creating a heat-affected zone. Waterjet uses high-pressure water and abrasive particles with no heat at all. This makes waterjet the preferred choice for thick plate, heat-sensitive alloys, hardened materials, and non-metal materials. Laser is generally faster and more economical for thin to mid-gauge steel and aluminum sheet production.
How thick can waterjet cut?
Waterjet can cut steel plate up to 6 inches or more, though cutting time increases significantly with thickness. For production work on thick plate, 1 to 3 inches is the practical sweet spot where waterjet offers clean cuts at reasonable cycle times. Above 3 inches, expect some taper on the cut edge unless the machine has a tilting head to compensate.
Does waterjet cutting leave burrs or require deburring?
Waterjet-cut edges are generally smooth with minimal burr on most materials. The abrasive action produces a matte texture rather than the smooth bright finish of a fine laser cut, but the edge is clean enough for most structural and functional applications without secondary deburring. For tight mating surfaces or cosmetic edges, light hand deburring at specific features may be needed.
Can waterjet cut non-metal materials like rubber or plastic?
Yes. Waterjet cuts rubber, HDPE, UHMW, nylon, composites, and fiberglass cleanly without edge melting. For soft materials, a pure water jet without abrasive is sometimes used. This makes waterjet useful for shops that need to cut gaskets or composite panels alongside metal parts in the same program.