How to choose a steel and not overpay

If the whole conversation about steel grades comes down to one observation, it is an unpleasant one: the grade of steel is not the most important parameter of a kitchen knife. Below is what matters more, and the order in which to think about it.

Hardness is easy to measure and therefore overrated

Rockwell hardness is a measure of resistance to local indentation: a ball or a diamond cone is pressed into the surface and the relative depth of the mark is read off. Steels use scale C, hence figures like 61 HRC.

There is a handy rule: every two points of hardness roughly double the time a knife holds its edge. A knife at 52 HRC stays sharp about a week, a knife at 62 HRC around a year with regular use. The rule is crude and idealised, but it gets the scale right.

The trouble is that hardness on its own guarantees nothing. A steel that is too hard, without the additions that give toughness, simply crumbles. What you need is high hardness and high toughness at once, and those two pull in opposite directions; steelmakers have spent their whole lives looking for the optimum between them.

The dichotomy you can’t get around

Wear resistance is set by the hardness of the steel, the hardness of the carbides and how many of them there are. More carbides, longer edge retention. But carbides are hard and brittle: they also make it easier for cracks to start, which means a chipping edge and broken tips.

The only legitimate way around this is carbide quality, not quantity. Vanadium carbide is one of the hardest there is, and if you keep the carbides fine, the same carbide volume buys more wear resistance. Hence the conclusion the industry arrived at: the best balance of properties comes from powder steels alloyed mainly with vanadium.

Stainless steel pays for not rusting. Chromium is tied up in chromium carbides — softer than vanadium ones and larger, so they spoil both wear resistance and toughness. This can be worked around only partly: less chromium, additions of molybdenum, niobium and nitrogen. So the “stainless versus carbon” argument is meaningless as posed — what matters is which stainless, which carbon steel, and which property you are comparing them on.

Heat treatment matters more than the grade

The same steel from different makers means different knives. Shirogami White #1 gives anywhere from 60 to 65 HRC depending on the hardening. S30V ruined its reputation on exactly this: the steel is demanding about heat treatment, and some knives came out either too soft or prone to chipping.

A separate case is knives made in China from imported Japanese steel. The price is attractive, the quality is not consistent: poor command of the technology means the steel is often hardened wrong and ground on wheels without water cooling. Overheating lowers hardness. VG-10 in a Japanese knife gives 60–61 HRC; in a Chinese one it can turn out noticeably softer, and then the knife is no harder than an ordinary one at half the price.

What not to buy

• “Surgical steel” — no official grade of that name exists. Real medical alloys are very rust-resistant but lack the properties a knife needs. In practice the words “surgical steel” mean 420 or worse.
• The 420 series — very rust-resistant and too soft for a kitchen: it has little carbon. Its place is in a diving knife, not on a board.
• 440A and 440B — a great many inexpensive knives are made from them, but as a cutting material the steel is weak.
• X50CrMoV15 and relatives — very rust-resistant and unremarkable in every other way. Carbon around 0.5%, sharpness holds badly, sharpening will be constant.
• 440C — a borderline case. With good heat treatment an excellent kitchen steel, with bad heat treatment unusable.

This list is useful because it closes off the bottom half of the market in one move. Beyond it the sensible options begin, and the differences between them are no longer as dramatic as the difference between them and this list.

How it works for people who earn a living with a knife

It is worth looking at a professional kitchen, because there the economics are visible without decoration. Cooks in canteens, restaurants and meat departments work with knives of cheap carbon steel, made from rolled stock rather than forged. There are many knives: one for each type of product, marked something like “RR” for raw fish or “CM” for cooked meat. Hygiene and time saved on washing up matter more than any specification.

The edge is trued with a steel before every approach to the workstation — a movement drilled to automatism, done in seconds. After the shift the knife is washed, wiped, lightly oiled with food-grade fat and put back in its place. No sane restaurant owner is going to buy seven or eight identical luxury-class knives of each type for every cook.

The European tradition is built on soft steel in general: professional kitchens true a knife daily or several times a day. Soft steel plus daily truing isn’t backwardness, it is an engineering decision for a particular working regime.

Where expensive steels actually live

Knives from exotic alloys are a domestic item. Their main purpose is to give pleasure in use, not to earn a cook his bread.

That is exactly why all expensive knives are made with attention to appearance, sometimes to the point of absurdity. Finding a knife of expensive Japanese steel with a normal European handle and none of the secondary flourishes — the deliberately rough-finished spine and other decorations “for authenticity” — is nearly impossible. An ordinary cook who stands all day in heat and damp has no use for a knife that can’t be dropped, whose handle can’t get wet, and which is easy to steal.

How to choose

The order of questions is roughly this:

• Are you willing to wipe the blade dry? If not, the whole carbon and semi-stainless half of the catalogue drops out at once, and the choice runs among stainless steels only.
• How often are you willing to sharpen? If you have stones and the habit of using them, high wear resistance isn’t needed — it is needed by people who don’t want to sharpen and don’t know how.
• What do you sharpen with? High-carbide powder steels resist abrasive just as they resist food. A knife you can’t maintain is a blunt knife.
• Who hardened it? The spread of hardness within one grade can be larger than the difference between grades.
• At what angle? Tool steels don’t tolerate too narrow an edge, and that is a design limit, not an invitation to experiment.

And one last thing. The difference between a good steel and a very good one is felt in the kitchen far less than the difference between a sharpened knife and an unsharpened one. Someone who runs a blade over a stone once a week cuts better than someone with an S110V knife last sharpened in the shop. It is a boring conclusion, but it costs nothing.