Yes, a waterjet can cut hardened tool steel such as 60 HRC without affecting its hardness. This is one of the most significant advantages of waterjet cutting over thermal processes.

Hardened tool steel is used for dies, molds, punches, and cutting tools. Maintaining its surface hardness is critical for performance. Laser cutting, plasma cutting, and electrical discharge machining all generate significant heat. Laser and plasma create a heat-affected zone where the steel reaustenitizes and then quenches, producing a brittle martensitic layer or softening the material. Electrical discharge machining creates a recast layer that is often softer than the base material. Waterjet cutting produces no heat. The cutting mechanism is purely mechanical erosion. There is no heat-affected zone, no metallurgical change, and no softening of the cut edge.

The waterjet stream mixes high-pressure water with garnet abrasive. The abrasive particles strike the steel surface at high velocity, removing microscopic chips through impact and micro-cutting. The steel experiences no temperature rise above ambient because the water continuously cools the cutting zone. Any friction heat is instantly carried away by the water jet. The hardness of 60 HRC tool steel remains exactly 60 HRC from the surface through the cut edge and into the interior.

Cutting hardened tool steel requires abrasive waterjet with appropriate parameters. The pump should operate at 55,000 to 60,000 psi. A 0.014 inch or 0.015 inch water orifice paired with a 0.040 inch mixing tube is standard. Abrasive flow rate should be 1.0 to 1.5 pounds per minute of 80 mesh garnet. Cutting speed depends on thickness. For 0.25 inch thick hardened tool steel, speeds of 5 to 8 inches per minute are typical. For 0.5 inch thickness, speeds drop to 2.5 to 4 inches per minute. For 1 inch thickness, speeds of 1 to 2 inches per minute are expected.

Edge quality on hardened tool steel is excellent. The cut surface has a matte, sandblasted appearance with no recast layer, no oxide scale, and no discoloration. The kerf taper is typically 0.002 to 0.005 inches per side, which is acceptable for most tooling applications. If a zero-taper edge is required, the waterjet can tilt the cutting head to compensate automatically.

One practical consideration is the wear resistance of the tool steel itself. Hardened steel erodes slower than annealed steel of the same composition. Cutting speeds on 60 HRC material are approximately 30 to 40 percent slower than on the same steel at 20 HRC. This is expected and simply requires longer cutting times.

Piercing hardened tool steel needs care. The waterjet should start piercing slightly away from the cut line or use a ramp-in from the edge. Direct piercing through the full thickness can create a small divot. For precision tools, piercing in a scrap area or using a lead-in cut prevents any mark on the finished part.

After cutting, the tool steel part requires no post-cut heat treatment. The hardness remains unchanged. The part can be used directly as a die, punch, or mold component. For applications requiring a very smooth surface, light grinding or lapping removes the slight surface roughness left by the waterjet.

Waterjet cutting is particularly valuable for prototype tooling and short-run stamping dies where traditional machining would require annealing, cutting, and re-heat treating. Cutting directly from hardened stock eliminates multiple processing steps and reduces lead time from weeks to hours.