---
type: process
name: "Water Jet Cutting"
category: "Cutting"
subcategory: "Mechanical"
materials: ["Metal", "Plastic", "Glass", "Ceramic", "Composite", "Wood"]
tolerances: "±0.005 in (±0.13 mm) typical on thin material; ±0.003 in (±0.076 mm) achievable; ±0.010–0.020 in (±0.25–0.5 mm) on thick plate; 1–3° of natural taper unless a compensating head is used"
volumes: "1–5,000 parts; no tooling, so single pieces are routine"
lead_time: "1–5 business days; often same-week for single parts"
url: https://manufacturingprocesses.org/processes/cutting/water-jet-cutting
---

# Water Jet Cutting

Water jet cutting drives a high-pressure jet of water and abrasive through the material, cutting almost anything with no heat-affected zone.

- **Category**: [Cutting](https://manufacturingprocesses.org/processes/cutting.md)
- **Family**: Mechanical
- **Materials**: Metal, Plastic, Glass, Ceramic, Composite, Wood
- **Typical tolerances**: ±0.005 in (±0.13 mm) typical on thin material; ±0.003 in (±0.076 mm) achievable; ±0.010–0.020 in (±0.25–0.5 mm) on thick plate; 1–3° of natural taper unless a compensating head is used
- **Surface finish**: Edge quality is specified on a Q1–Q5 scale, from a fast separation cut with visible striations to a slow finish cut with a nearly striation-free face; roughness increases toward the exit side of the cut
- **Typical volumes**: 1–5,000 parts; no tooling, so single pieces are routine
- **Lead time**: 1–5 business days; often same-week for single parts

## Overview

Water jet cutting drives water through a jeweled orifice at **60,000 psi (4,100 bar)** — 90,000 psi (6,200 bar) on high-pressure pumps — and, for anything harder than foam, entrains garnet abrasive into the stream in a mixing tube. The resulting jet erodes its way through material rather than melting it, so there is **no heat affected zone at all**: hardened steel keeps its temper, aluminum does not distort, and composites do not delaminate from heat.

It is the most material-agnostic cutting process available. The same machine cuts 6 in (150 mm) steel plate, glass, stone, titanium, carbon fiber, rubber gasket stock and food.

Kerf is **0.030–0.060 in (0.76–1.5 mm)**, wider than a laser and narrower than plasma. Tolerance is **±0.005 in (±0.13 mm)** on thin material with modern control, opening as thickness grows.

## How it works

1. **Pressure generation.** An intensifier or direct-drive pump raises water to 60,000 psi (4,100 bar). The high-pressure plumbing, seals and check valves are the machine's main maintenance burden.
2. **Orifice.** Water passes through a ruby, sapphire or diamond orifice of **0.010–0.014 in (0.25–0.35 mm)**, emerging as a coherent jet at roughly two to three times the speed of sound in air.
3. **Abrasive entrainment.** For metals, stone, glass and composites, garnet — most commonly **80 mesh** — is drawn into a mixing chamber and accelerated down a carbide mixing tube of **0.030–0.045 in (0.76–1.1 mm)** bore. That mixing tube bore sets the kerf. Soft materials such as foam, gasket, felt and food are cut with pure water and a much finer kerf.
4. **Piercing.** The jet pierces from a standing start, often with a lower-pressure ramp or a slight dwell on brittle material to avoid cracking or delamination.
5. **Cutting and quality selection.** Feed rate is chosen from a quality scale, conventionally **Q1 to Q5**: Q1 is a fast separation cut with pronounced striations at the bottom edge, Q5 is a slow finish cut with a nearly striation-free face. Moving from a separation cut to a finish cut can cut feed rate several times over.
6. **Taper control.** The jet loses energy with depth, so the kerf is naturally wider at the top — roughly 1–3° on a fixed head. Tilting taper-compensation heads swing the jet to bring the cut face back to near-perpendicular.
7. **Catcher tank and abrasive removal.** Spent garnet settles in the tank and is periodically removed. Abrasive consumption of roughly 0.5–1.0 lb/min (0.23–0.45 kg/min) is a direct, continuous consumable cost.

## Design guidelines

### Minimum hole and slot size
Keep holes at least **1× material thickness** in diameter and never smaller than about 1.5× the kerf. A hole narrower than the jet cannot be cut at all, and one only slightly larger comes out tapered and rough because the jet has no room to develop.

### Expect and control taper
A fixed head leaves **1–3° of taper**, wider at the entry side. On parts where the cut face is a mating or sealing surface, either specify a taper-compensating head or state which face is dimensionally controlled. On thin material taper is negligible; on 2 in (50 mm) plate it is a real dimension.

### Choose an edge quality deliberately
Striations increase with thickness and feed rate, so the bottom of a thick cut is always rougher than the top. Specify the quality level you need rather than the best available — a Q3 cut on a bracket outline and a Q5 cut only on the one edge that seals is far cheaper than Q5 everywhere.

### Use the absence of a heat affected zone
This is the reason to choose water jet over laser or plasma. Pre-hardened, tempered, plated or heat-treated stock can be cut without altering it, and there is no recast, no hardened cut edge to spoil a subsequent tapping operation, and no delamination on composites.

### Stack thin sheets, but only when the material allows
Multiple sheets of the same material can be clamped and cut in one pass, dividing cost per part — specify stock from the [sheet metal gauge chart](/charts/sheet-metal-gauge-chart) so every layer is the same nominal thickness. Sheets must be tightly clamped — any gap lets the jet spread between layers and taper the lower sheets.

### Watch for delamination and brittle fracture at pierce points
Laminates, composites and glass can crack at the pierce. Pierce in scrap and lead in, or use a low-pressure pierce, and expect the shop to ask for a lead-in allowance around every internal cutout.

| Material | Water jet suitability | Notes |
|---|---|---|
| Steel, stainless, tool steel | Excellent | To ~6 in (150 mm) practical; keeps temper, no recast |
| Aluminum | Excellent | No thermal distortion on thin or long parts |
| Titanium, Inconel | Excellent | Common in aerospace where HAZ is unacceptable |
| Glass, stone, tile | Excellent | Low-pressure pierce required to avoid cracking |
| Carbon fiber, G10, laminates | Excellent | No heat delamination; abrasive wear on tooling is nil |
| Foam, rubber, gasket, felt | Excellent | Pure-water cutting, no abrasive, very fine kerf |
| Copper, brass | Excellent | No reflectivity problem, unlike laser |
| Tempered glass | Not possible | Shatters; must be cut before tempering |
| Very thin sheet under 0.020 in | Marginal | Jet deflection makes laser cutting more accurate |

| Feature | Recommended | Limit | Why |
|---|---|---|---|
| Hole diameter | ≥ 1× thickness | ~1.5× kerf, 0.060 in (1.5 mm) | Jet needs room to cut a full circle |
| Material thickness | ≤ 2 in (50 mm) | ~6 in (150 mm) practical | Speed and taper degrade with depth |
| Internal corner radius | ≥ 0.5× kerf | Kerf radius | The jet is round |
| Edge taper allowance | 1–3° | Near zero with a tilting head | Jet energy falls with depth |
| Web between features | ≥ 1× thickness | 0.5× thickness | Jet spread and part stability |

## Cost drivers

Water jet is priced by the minute, and the minute is set by material, thickness and the edge quality you ask for.

**Thickness times cut length.** Feed rate falls steeply with thickness. A 2 in (50 mm) plate profile can take ten times as long as the same profile in 0.25 in (6 mm) stock.

**Edge quality.** The quality scale is a feed rate multiplier. Cutting an entire part at finish quality when only one edge seals is the single most common source of avoidable cost.

**Abrasive.** Garnet flows continuously at roughly 0.5–1.0 lb/min (0.23–0.45 kg/min) whenever the jet is on, and it is consumed, not recycled, on most machines.

**Pierce count.** Each internal cutout requires a pierce, which is slower than cutting and harder on the mixing tube.

**Consumables and maintenance.** Orifices, mixing tubes and high-pressure seals wear continuously and are built into the hourly rate.

Four ways to take cost out:

1. Specify finish quality only on the edges that need it and separation quality everywhere else.
2. Stack thin sheets of the same material so one cut produces several parts.
3. Reduce internal cutouts, or enlarge and consolidate them, to cut pierce count.
4. If the part is thin steel with no heat sensitivity, compare against [laser cutting](/processes/cutting/laser-cutting) — water jet earns its rate on thickness, hardness and heat-sensitive materials, not on thin mild steel.

## FAQ

### How thick can a water jet cut?

About 6 in (150 mm) in steel is the practical limit, with thicker cuts possible but slow enough to be uneconomic. Feed rate falls steeply with thickness, so a 2 in (50 mm) profile can take roughly ten times as long as the same profile in 0.25 in (6 mm) stock. Softer materials such as foam and gasket stock cut far thicker.

### What tolerance does water jet cutting hold?

±0.005 in (±0.13 mm) is typical on thin material with a modern controller and ±0.003 in (±0.076 mm) is achievable. On thick plate it opens to ±0.010–0.020 in (±0.25–0.5 mm), partly because the cut face carries 1–3° of natural taper unless a tilting taper-compensating head is used.

### Does water jet cutting produce a heat affected zone?

No. The jet erodes material mechanically rather than melting it, so there is no heat affected zone, no recast layer and no hardened cut edge. This is the reason to choose it for pre-hardened stock, heat-treated or plated material, composites that would delaminate, and long thin parts that would distort from thermal cutting.

### What is the minimum hole size for water jet cutting?

About 1× the material thickness in diameter, and never smaller than roughly 1.5× the kerf — around 0.060 in (1.5 mm) with a typical 0.040 in (1 mm) kerf. A hole narrower than the jet cannot be produced, and one only slightly larger comes out tapered and rough.

### What does water jet edge quality Q1 to Q5 mean?

It is a feed rate scale. Q1 is a fast separation cut that leaves pronounced striations toward the exit side of the material; Q5 is a slow finish cut with a nearly striation-free face. Because it is a speed multiplier, specifying Q5 across an entire part when only one edge seals is the most common avoidable cost on a water jet quote.

### What materials cannot be water jet cut?

Tempered glass shatters and must be cut before tempering. Very thin sheet below about 0.020 in (0.5 mm) is cut more accurately by laser because jet deflection dominates. Otherwise the process is close to material-agnostic: metals, stone, glass, ceramics, composites, rubber, foam and food are all routine.

## Alternative processes

- [Laser Cutting](https://manufacturingprocesses.org/processes/cutting/laser-cutting.md): Laser cutting melts, burns or vaporises a narrow kerf through flat stock with a focused beam, producing profiles from a 2D file with no tooling.
- [Plasma Cutting](https://manufacturingprocesses.org/processes/cutting/plasma-cutting.md): Plasma cutting blows an ionised gas jet through conductive metal, melting and ejecting a kerf far faster than a laser on thick plate.
- [Electrical Discharge Machining](https://manufacturingprocesses.org/processes/cutting/electrical-discharge-machining.md): EDM erodes conductive metal with controlled electrical sparks across a dielectric gap, cutting hardened material and sharp internal corners.
- [Punching and Blanking](https://manufacturingprocesses.org/processes/cutting/punching-and-blanking.md): Punching and blanking shear sheet metal between a punch and a die, producing holes and flat outlines at very high speed.
- [Sawing](https://manufacturingprocesses.org/processes/cutting/sawing.md): Sawing separates stock with a toothed blade — band, circular or cold saw — and is the default first operation on bar, tube and plate.

## Related processes

- [Laser Cutting](https://manufacturingprocesses.org/processes/cutting/laser-cutting.md): Laser cutting melts, burns or vaporises a narrow kerf through flat stock with a focused beam, producing profiles from a 2D file with no tooling.
- [Plasma Cutting](https://manufacturingprocesses.org/processes/cutting/plasma-cutting.md): Plasma cutting blows an ionised gas jet through conductive metal, melting and ejecting a kerf far faster than a laser on thick plate.
- [Electrical Discharge Machining](https://manufacturingprocesses.org/processes/cutting/electrical-discharge-machining.md): EDM erodes conductive metal with controlled electrical sparks across a dielectric gap, cutting hardened material and sharp internal corners.
- [CNC Milling](https://manufacturingprocesses.org/processes/cutting/cnc-milling.md): CNC milling removes material with a rotating multi-flute cutter moved along programmed paths, producing prismatic parts from solid stock.
- [Sheet Metal Fabrication](https://manufacturingprocesses.org/processes/forming/sheet-metal-fabrication.md): Sheet metal fabrication cuts, bends and joins flat stock into a finished assembly, typically laser cutting followed by press braking, hardware and welding.

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*Source: [Manufacturing Processes](https://manufacturingprocesses.org/processes/cutting/water-jet-cutting)*

*Last updated: August 11, 2026*