The blades leave our workshop twice
Most knife makers heat treat in house. It is the natural thing to do — you cut the steel, you grind it, you harden it, you finish it. One roof, one process, full control.
We do it differently, and it costs us time and freight on every single batch. Our ground blades go back to the steel mill that made the steel, are heat treated there, and come back to us for finishing.
Here is why that is worth the extra step.
Where our steel comes from
We buy directly from Voestalpine, the Austrian steel group that includes both Böhler and Uddeholm. N690, Elmax, M390, Vanax, Sleipner, AEB-L, Vanadis 4 Extra — these are their steels, made to their specification.
Buying direct from the mill means we know exactly what alloy is in every blade, in what condition it arrived, and from which batch. There is no distributor in between, and no uncertainty about what the steel actually is.
What happens in our workshop
The steel arrives as sheet. We laser cut the profiles in our own shop, which gives us clean, repeatable outlines and lets us adjust a design without waiting on anybody.
Then the grinding. Every blade is hand ground on belt grinders using jigs we made ourselves — a jig for each profile, so the bevel lands in the same place on the hundredth blade as on the first. Selected full flat models are CNC ground where the geometry demands it.
Hand grinding with jigs is slower than a fully automated line and more consistent than freehand. It is the compromise we chose deliberately.
At this point the blade has its shape and its geometry. What it does not have is hardness. Ground steel in its annealed state is soft — you could bend it.
And then they go back
The ground blades are packed and shipped back to Voestalpine for heat treatment. The mill that made the steel hardens the steel.
Not a subcontractor. Not our own oven. The metallurgists who wrote the datasheet.
Why this matters: vacuum furnaces
Voestalpine heat treats in industrial vacuum furnaces. The difference between that and a workshop oven is not marginal.
No oxidation. In a vacuum there is no oxygen, so no scale forms and no carbon is lost from the surface. A blade hardened in open air develops a decarburised skin — a soft outer layer that has to be ground away, and if you do not remove all of it, the edge is softer than the rest of the blade. In a vacuum furnace, the surface comes out as clean as it went in.
Even temperature across the whole load. These furnaces hold temperature uniformly across hundreds of blades. A small oven has hot spots and cold spots, which means blades from the same batch come out at different hardnesses. Ours do not.
Controlled quenching. High pressure gas quenching, at a rate specified for each alloy. Too slow and the steel does not reach full hardness; too fast and it warps or cracks. The rate is set by the people who determined what it should be.
Documented and repeatable. Every cycle is recorded. A batch of N690 we send this month gets the same treatment as one we sent last year.
The cryogenic step
For our powder metallurgical steels — Elmax, Vanax, M390 and Vanadis 4 Extra — the process includes a cryogenic stage: after quenching, the blades are cooled far below freezing before tempering.
The reason is retained austenite. When high alloy steel is quenched, not all of the structure converts to martensite, the hard phase you want. Some austenite remains, and it is soft. Worse, it is unstable — it can convert later, in use, causing dimensional change and a blade that loses its edge in ways that are hard to explain.
The cryogenic step converts that retained austenite while the blade is still in process, where it belongs. The result is higher achieved hardness, better dimensional stability, and an edge that behaves the same in year five as in week one.
This step matters for powder metallurgical steels and is not needed for the others. We apply it where it does something, and not where it would only add cost.
What comes back, and what we do with it
The blades return hardened, clean and stable. We finish them: surface work to 400 grit, hand satin finishing with Scotch-Brite on selected models, a stonewash finish on some Sleipner profiles.
Then every blade is sharpened. Not "edge ready to be sharpened" — actually sharpened, at 400 grit, ready to cut when it reaches you.
And if you want a name on it, we laser engrave it free of charge.
Why we can publish a hardness figure
This is the practical payoff. Because the heat treatment is done in documented industrial furnaces by the mill that made the steel, we know what hardness we get, and we are willing to print it:
- 1.4116 — 54 to 57 HRC
- N690 — 58 to 60 HRC
- AEB-L — 60 HRC
- Sleipner — 60 to 62 HRC
- Elmax — 60 to 61 HRC
- Vanax — 60 HRC
- M390 — 60 to 61 HRC
- Vanadis 4 Extra — 63 to 64 HRC
Look at how blade blanks are usually sold and you will notice how rarely a number appears. "Heat treated." "Hardened." "Consistent hardness." Those phrases are not measurements.
We publish the number because we know it.
The cost of doing it this way
Freight in both directions. Waiting on the mill's schedule rather than our own. Batch sizes set by someone else's furnace rather than by our day's work.
The alternative would be a heat treating oven in our workshop and full control of our own timeline. It would be faster and cheaper, and the blades would not be as good.
When you buy a blade blank, heat treatment is the one thing you cannot inspect. You can see the grind. You can feel the edge. You cannot see whether the steel reached the right temperature, held it long enough, quenched at the right rate, or converted its retained austenite.
You are trusting somebody. We would rather that somebody was the mill.
Our blade blanks ship ground, vacuum heat treated and sharpened, with the hardness printed on every product page. If you want to understand what those numbers mean, our guide to blade hardness goes through each steel in detail.