Waterjet cutting is renowned for its ability to cut extremely thick materials, far beyond the practical limits of laser or plasma. However, actual maximum thickness depends on pump pressure (typically 60k, 90k, or 120k psi), abrasive quality, and acceptable cutting speed for your production needs.

Steel: For mild steel, a modern 90k psi abrasive waterjet can cut up to 12 inches (300 mm) thick, though production speeds become very slow. At 60k psi, practical maximum is around 6–8 inches (150–200 mm). For hardened tool steel or stainless steel, expect slightly lower limits due to higher material strength. Many users stay below 4 inches (100 mm) for reasonable cycle times.

Aluminum: Aluminum cuts faster and thicker than steel because it is softer. A 90k psi waterjet can easily cut aluminum up to 10–12 inches (250–300 mm). With 60k psi, 8 inches (200 mm) is achievable. Unlike steel, aluminum does not experience heat-affected zones, so thick plates cut cleanly without warping or metallurgical change.

Stone (Granite, Marble): Natural stone is an ideal waterjet material. Granite up to 6–8 inches (150–200 mm) is common with 60k psi, while 90k psi pushes to 10–12 inches (250–300 mm). Marble cuts slightly thinner due to fracturing risk. However, cutting stone thicker than 4 inches becomes very slow, and edge taper becomes more pronounced.

Key takeaway: For all materials, maximum thickness is a trade-off with cutting speed. A waterjet can technically cut 12-inch steel, but it may take hours per linear foot. Most production shops optimize for thicknesses where cutting time remains economical.