Bioline 4C27A is a hardenable, free-machining martensitic stainless steel purpose-built for precision blade applications, most notably surgical and medical blades where a consistent, fine, low-defect microstructure and a controllable, repeatable hardened edge matter more than bulk corrosion resistance. It corresponds to DIN X22CrMoNiS13-1 and is commonly cross-referenced to a modified 420F (420F MOD) chemistry — the "F" indicating a free-machining, sulfur-added grade rather than the standard low-sulfur 420.

With roughly 13% chromium plus additions of molybdenum and nickel, Bioline 4C27A has enough hardenability and corrosion resistance for single-use and reusable surgical blades, scalpel components, and other precision cutting instruments that need to take and hold a very fine edge after hardening and tempering. Like other straight martensitic stainless grades, it is supplied and normally machined in the annealed condition, then hardened and tempered afterward to develop its final cutting-edge hardness.

The elevated sulfur content is deliberate — it is a free-machining addition typical of "F"-suffix 420-family grades, trading some corrosion resistance and edge-toughness for more consistent chip control during precision blade manufacturing.

Bioline 4C27A is engineered to machine better than standard 420 thanks to its sulfur addition, which forms manganese sulfide inclusions that act as internal chip breakers and lubricate the cutting zone. In the annealed condition this makes it noticeably more forgiving than non-free-machining martensitic grades: shorter, more manageable chips, lower cutting forces, and better surface finish at a given feed rate. It still behaves like a chromium martensitic stainless in every other respect — moderate work hardening if the edge is allowed to rub, and low thermal conductivity that concentrates heat at the tool tip.

Because this alloy exists specifically to be shaped into thin, precise blade geometries before hardening, dimensional consistency and surface finish in the annealed condition matter as much as raw material removal rate. Sharp, positive-rake tooling with good coolant delivery minimizes built-up edge and preserves the fine surface finish the subsequent hardening and grinding operations depend on. Once heat treated to its final blade hardness, cutting forces rise substantially and machining is generally limited to grinding rather than turning or milling.

Values are for the annealed condition. Assume favorable conditions: a well-matched insert grade, rigid tool and workpiece clamping, good raw material quality, short tool overhang, and adequate coolant.

Turning

Parting / Grooving

Milling