There's a belief that runs through every knife forum: that sharpening is all skill. Learn the angles, buy the right stones, put in the hours, and you can make any knife scary sharp and keep it that way. The other half of the belief is that a higher price buys a sharper edge. Both are part true and mostly wrong, and untangling them is the whole point of this one.

Part One covered geometry — why a thin edge cuts with less force. Part Two covered why that edge dulls, and how geometry trades keenness against durability. Both of those are decided before the knife reaches your stones. This part is about the third thing that's already decided: the steel itself, and the hard ceiling it puts on what any amount of skill can do.

How It Actually Works

Steel Isn't One Thing

Most people picture steel as a single smooth substance, uniform all the way through. At the scale of an edge, it's nothing like that. Steel is a composite. There's a base — the matrix, mostly iron with carbon dissolved into it — and scattered through that base are carbides: tiny particles much harder than the matrix around them. How big those carbides are, how evenly they're spread, and how hard the matrix holding them is — those are what decide the kind of edge the steel can take.

Picturing tiny particles suspended in a matrix doesn't come naturally to everyone, so here's another way in. Imagine taking a saw to a concrete slab and looking at the cut face — the "cross-section." What you'd see is fine sand bound together, with larger chunks of aggregate mixed through it. The sand is your matrix; the aggregate is your carbides. Now imagine narrowing that block down to an edge — to the honed edge, like the inside of a funnel. What happens at the very point depends entirely on the aggregate.

If the aggregate is large, those chunks can't fit down into the tip of the funnel. The very point ends up made of binder with nothing bracing it — and it crumbles the moment you ask anything of it. If the aggregate is fine and, just as important, uniform, it packs all the way down toward the point and supports it. Mismatched sizes pack randomly and leave weak pockets where the edge fails first. Even, fine aggregate packs dense and holds its shape. Same material — completely different edge, decided by the size and consistency of what's inside it.

That's carbides in steel exactly. A steel with large, uneven carbides can be very wear-resistant — the chunks are hard and slow to grind away — and still be unable to take or hold a genuinely fine edge, because at the honed edge a big carbide tears out and leaves a gap. A steel with fine, uniform carbides can be sharpened thinner and keep that thin edge intact.

Hardness is the dial you can feel most directly, and you can test it without a knife at all.

The Trade-Off You're Paying For

Why You Pay for Powder

So how do you get fine, uniform carbides? It comes down to how the steel was made. In traditional steel, the alloy is melted and poured into an ingot that cools slowly. As it cools, carbides have time to clump and grow — large, and unevenly spread, like aggregate that settled before the concrete set. It's perfectly good steel for plenty of jobs. It just carries a low ceiling on how fine an edge it can hold.

Powder metallurgy changes the cooling. The molten steel is blasted into a fine powder, and each tiny droplet freezes almost instantly — too fast for carbides to grow or clump. What you get is steel shot through with very small, very evenly distributed carbides. That's what the higher price is buying: not a secret alloy, but a finer, more uniform structure of the same ingredients. It's what lets a steel be wear-resistant and capable of a thin, stable edge — two things that fight each other in conventional steel.

S35VN is a worked example of this. It's made with particle metallurgy, so its carbides start out fine and uniform. It also carries a deliberate measure of niobium, which forms especially small, hard carbides — a refinement aimed squarely at edge stability and toughness, so the honed edge resists both rolling and chipping. Run to around 60–62 HRC, the matrix is hard enough to hold a fine edge without folding, but not so hard it turns glassy and chips. None of that makes it the most wear-resistant steel you can buy. It makes it a steel that takes a clean edge, holds it through real use, and comes back without a fight — which is a different target, and the right one for a knife you carry.

The Honest Ceiling

What No Technique
Can Overcome

Here's the part that reframes most of what people argue about. You cannot sharpen past your steel. Technique — the right angle, a clean progression of grits, a properly removed burr — gets you to the finest, most durable edge a given steel is capable of. It cannot take you beyond it. A soft, coarse-carbide steel sharpened by an expert will not hold an edge the way a fine-carbide steel sharpened adequately will. The steel sets the ceiling. Your hands decide how close to it you get.

And the alloy isn't even the whole ceiling — how it was heat-treated sets it just as much. The same steel, hardened well or poorly, becomes two different knives. This is where a step like cryogenic treatment earns its place: chilling the steel far below zero after hardening converts more of its structure into the hard, stable form you actually want, more uniformly — pushing the steel closer to the ceiling its chemistry promises. We covered the why and how of powdered metal and cryogenic treatment on their own, if you want the deeper version: why USA powdered metal, and what cryogenic heat treatment does. The short version: alloy plus heat treatment together draw the line your technique then works inside of.

What It Means for Your Carry

The Best Steel Isn't
the Hardest Number

This quietly dismantles the steel arms race. The steel with the highest wear-resistance number on a chart is usually packed with coarse, hard carbides — excellent for slicing abrasive material all day, miserable to sharpen, and often brittle at a fine edge. For most carry, that's the wrong ceiling. What you actually want is a steel whose ceiling matches how you live with a knife: takes a fine, stable edge, holds it through a careless week, shrugs off the moisture in a pocket, and sharpens back without specialized gear or a lost afternoon.

That's a balanced steel at a sensible hardness — not the one that wins a spec-sheet bragging contest. The "best" steel was never the hardest or the most wear-resistant. It's the one whose limits line up with the way the knife is actually carried and maintained.

Where the Three Meet

Geometry, Steel, and
the Hand That Sharpens

Three things decide an edge, and now you've seen all three. Geometry is the frame — how thin, what angle. Steel is the ceiling — the finest, most durable edge that frame can hold. Technique is how close to the ceiling you bring it. Miss any one and the other two can't cover for it: a perfect angle on the wrong steel, or a fine steel ground too thin for the work, both fail in the pocket just the same.

It's also why the steel question, for the MERINO line, was never about chasing the highest number — it was about choosing the ceiling that fits a knife built to actually be carried. Why S35VN specifically, out of everything on the table, and what that choice cost, is a decision with its own story.