Waterjet Cutting Tool Steel: A2, D2, O1, H13, and S7 Blanks

The standout capability of waterjet on tool steel is that it cuts the metal hardened. Because the abrasive removes material by erosion, hardness is almost irrelevant to whether the cut succeeds; a 62 HRC D2 plate cuts about as readily as the same plate annealed. This lets shops harden a plate first and waterjet the profile afterward, avoiding the dimensional changes that heat treatment causes when you machine first and harden second. Just as important, the cut is cold. Tool steels are crack-sensitive and many are air- or oil-hardening, so a thermal cut creates a brittle untempered martensite layer or even quench cracks at the edge. Waterjet adds no heat, so there is no new martensite, no microcracking, and no risk of cracking an already-hardened plate. For high-alloy grades like D2 with heavy carbide content, the cold erosive cut is the safe way to get a profile without compromising the heat-treated condition.

A2 is an air-hardening cold-work steel with good dimensional stability, common for dies and gauges; it cuts cleanly and is often waterjet-cut in the annealed state then hardened, or cut hardened for stability. D2 is the high-carbon high-chromium cold-work workhorse, loaded with chromium carbides that make it wear-resistant and abrasive; it cuts a bit slower because those hard carbides resist erosion, but waterjet handles it where many processes struggle. O1 is the oil-hardening grade favored for low-distortion tooling and cuts readily. H13 is the hot-work die steel, tough and used for die-casting dies and extrusion tooling; it cuts well and the cold waterjet cut avoids adding thermal stress to a grade that lives a thermal-cycling life. S7 is the shock-resisting grade for punches and chisels, tough and impact-tolerant; it too cuts cleanly. Across all five, the waterjet's value is delivering a profiled blank without altering the heat treatment, whether the plate is annealed or fully hard.

Tool steel cuts at rates similar to other alloy steels: a 90,000 psi machine cuts 0.5 inch A2 at roughly 4-7 inches per minute at Q3, with D2 a bit slower due to its carbides. Tolerances run about +/-0.005 inch at 0.25 inch and +/-0.010 inch at 1 inch, with taper opening on thick cuts unless a tilting head corrects it. Hardened plate cuts at nearly the same rate as annealed, which is a defining advantage. Because tool steel parts almost always need precise final dimensions and surface finish, the standard workflow is to waterjet a net-near blank and finish-grind or wire-EDM to size. Leave 0.010-0.030 inch of grind stock on critical surfaces. Waterjet is frequently paired with wire EDM here: the waterjet does fast bulk profiling of the hardened plate and the wire EDM does the precision detail, which is faster and cheaper than EDMing the whole profile. For hardened tool steel, that two-step approach is a common and economical route.

Waterjet beats wire EDM on tool steel for speed and cost on bulk profiling: it cuts far faster, handles thick plate easily, and needs no starter holes for outside profiles. For roughing out die plates, mold details, and large hardened blanks, waterjet gets you to net-near for a fraction of the wire EDM machine time. It also cuts profiles too thick for practical wire EDM. Wire EDM wins where precision and surface finish are the requirement: tight tolerances under +/-0.001 inch, fine internal corners, and mirror finishes are EDM territory, not waterjet. The honest answer is they are complementary. Use waterjet to blank and rough the hardened tool steel fast and cheap, then finish the critical features by grinding or wire EDM. Cutting an entire intricate die detail to final tolerance on a waterjet alone is the wrong choice; using it to remove the bulk before the precision step is the right one.