October 23, 2026
Mold steel selection comes down to expected shot count more than any other factor. P20, a pre-hardened, general-purpose tool steel, is the standard choice for molds expected to run 300,000 to 1 million shots, common for mid-volume packaging programs. It machines relatively easily, holds a good finish, and costs less upfront than harder alternatives, but it wears faster under high-cavitation, abrasive-resin, or extremely high-volume conditions.
H13 is a hardened hot-work tool steel that holds up significantly longer under high shot counts, multi-million-cycle production, and resins with abrasive fillers or glass content. It costs more to machine and typically extends tooling lead time, but for a program running multiple years at high volume, the lower per-part tooling amortization usually justifies the upfront cost. If your annual volume is climbing past a few million units on a single tool, H13 is worth pricing out even if the initial quote runs higher.
420 stainless steel and similar grades show up in cosmetic and cannabis packaging tooling less for hardness and more for corrosion resistance and the mirror-polish finish it holds. Clear PET and glossy PP parts show every imperfection in the mold surface, and stainless resists the pitting and rust that can develop in high-humidity production environments or with certain resin additive packages over time. It's a finish-quality and longevity decision as much as a mechanical one.
We spec steel based on projected annual volume, resin abrasiveness, and surface finish requirement together, not a single factor in isolation. A low-volume cosmetic launch doesn't need H13; a multi-million-unit commodity bottle program usually shouldn't be tooled in P20 if the economics support the harder steel. If a quote doesn't specify which steel a mold is cut from, ask, it's one of the biggest levers on both tooling cost and how long that tool actually lasts before refurbishment.
For how mold design decisions interact with part geometry, see Wall Thickness, Draft Angles, and Gate Placement.
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