FV535 is a British "Firth Vickers" series precipitation-hardening martensitic stainless steel, and it belongs in a different family entirely from the Ni-Cr-Mo-V die steels that dominate this reference group. Where those grades are carbon tool steels hardened by conventional quench-and-temper, FV535 is a low-carbon, chromium-cobalt-nickel-molybdenum stainless alloy that develops its strength through age-hardening precipitation, not through carbon martensite alone. Chromium in the 10-11% range gives it genuine corrosion resistance, cobalt (roughly 5-7%) boosts high-temperature strength and secondary hardening response, and small additions of molybdenum, vanadium, niobium, and boron round out a composition built for demanding valve and turbine service.

This grade was developed specifically for exhaust valves, turbine components, and other parts that need to hold strength and creep resistance at elevated temperature while still resisting oxidation and corrosion — a combination plain tool steels can't offer. Its precipitation-hardening response lets it be solution treated, then machined in a relatively soft condition before final aging brings it up to working strength, similar in principle to other PH stainless families but tuned for higher-temperature service rather than general tooling.

FV535 is a proprietary British specification rather than a DIN/Wnr-registered grade; no verified Werkstoffnummer cross-reference is on file for this material.

FV535 machines like the precipitation-hardening stainless it is, not like a tool steel, and that distinction matters. Even in the solution-treated (pre-age) condition it has a pronounced tendency to work-harden under a dull edge or light, rubbing cuts — the same austenite-to-martensite transformation mechanics that make PH stainless grades strong in service also generate a hardened skin under the tool if cutting parameters are too conservative. That makes a sharp, positive-rake edge essential: light, low-rake, or heavily honed edges that might be fine on a plain alloy tool steel will burnish and work-harden this material, driving up cutting forces and shortening tool life on the very next pass.

The chromium and cobalt content also promote heat retention at the cutting edge rather than in the chip, similar to other stainless and superalloy-adjacent grades, so heat management matters more here than for the carbon and low-alloy die steels in this group. Coated carbide grades with sharp, positive geometry and good edge toughness are the right starting point; avoid dwelling or light finishing passes that ride on a worn edge. Because most FV535 tooling is machined before the final aging treatment, cutting is generally done in a moderate-hardness solution-treated state rather than fully soft or fully aged.

Speeds below are for the solution-treated (pre-age) condition. Reduce speeds and increase positive rake further if work hardening is observed.

Milling

Turning, parting, and grooving grade recommendations for FV535 are not on file for this material yet. Browse the full turning/parting collection below for a stainless-capable grade suited to your hardness and finish requirements.

Sharper, more positive geometry than typical for plain tool steels is recommended to minimize work hardening on this precipitation-hardening stainless grade.