Why Your Burrs Won't Stay Sharp

(And what we did about it)

Most grinder manufacturers coat their burrs. They'll tell you about TiN, DLC, or ta-C, impressive-sounding materials with genuinely impressive hardness ratings. What they won't tell you is that a hard coating on a soft substrate is like wrapping tissue paper in armour. Once the coating wears through, you're grinding on the soft metal underneath.

At Heys, we start with a different substrate entirely.

But first, let's talk about what everyone else is doing.

The Coatings Everyone Uses

Uncoated Stainless Steel

Hardness: ~150 HV
What it is: Iron, chromium, and nickel alloy
Looks like: Silver
Best for: Budget grinders you'll replace in a year
Cost: Baseline

This is what's under most coated burrs. Soft enough that you can scratch it with a knife. Fine for occasional use, but it dulls quickly under daily espresso grinding.

TiN (Titanium Nitride)

Hardness: ~2,000 HV
What it is: A ceramic coating applied through Physical Vapor Deposition, titanium reacting with nitrogen to form a thin, hard layer
Looks like: Gold
Best for: Regular pour-over use, medium roasts
Cost: 1×

The entry point for coated burrs. Durable, but outclassed by carbon-based coatings. You'll see this on mid-range grinders.

DLC (Diamond-Like Carbon)

Hardness: ~2,500 HV
What it is: A mix of sp² (graphite-like) and sp³ (diamond-like) carbon bonds
Looks like: Dark grey/black
Best for: Daily use across all roast levels, including espresso
Cost: 2×

Harder than TiN, with better low-friction properties. This is where most premium grinders stop.

ta-C (Tetrahedral Amorphous Carbon)

Hardness: ~5,000 HV
What it is: Up to 70% sp³ carbon, the same atomic structure as diamond
Looks like: Rainbow (interference patterns from the ultra-thin coating)
Best for: Heavy daily use, light roasts, long espresso grind sessions
Cost: 7×

The hardest coating available. Nearly identical to synthetic diamond at the molecular level. Exceptional wear resistance and the lowest friction of any coating.

Why Structure Matters: sp² vs. sp³

Carbon atoms can bond in two ways:

• sp² bonds (graphite): Strong, but they slide past each other, that's why pencil lead writes
• sp³ bonds (diamond): The strongest bonds in nature, arranged in a rigid lattice

The more sp³ content, the closer you get to actual diamond. DLC has some. ta-C has a lot. That's why ta-C outperforms everything else.

But here's the problem.

The Substrate Problem

All these impressive hardness numbers? They're measuring a coating that's only a few microns thick.

If you coat 150 HV stainless steel with 5,000 HV ta-C, you have a very hard surface on a very soft core. Under the pressure and heat of grinding, that soft substrate flexes. The coating cracks. You wear through to the stainless steel underneath, and suddenly you're grinding on 150 HV metal that dulls rapidly.

It's like coating a chocolate truffle in hard shell. Once you bite through, it's soft all the way down.

What We Do Differently

At Heys, we apply coatings to high-carbon chromium tool steel with a hardness of 620 HV, over four times harder than stainless steel.

This is a hard-boiled sweet, solid all the way through. The coating isn't protecting a soft core; it's enhancing an already tough substrate. When you combine 620 HV steel with ta-C coating, you get exceptional wear resistance that maintains burr geometry far longer than conventional approaches.

It costs more. It's harder to manufacture. But it means your burrs stay sharp for years, not months.

What This Means for Your Coffee

Dull burrs don't just grind slower, hey grind inconsistently. They produce more fines (dust) and boulders (large chunks), making it impossible to dial in a clean extraction. You get astringency, bitterness, or sourness that no amount of technique can fix.

Sharp burrs produce a narrow particle distribution. Clean extractions. Repeatable results. The coffee you intended to make.

The difference between a burr that lasts 500kg and one that lasts 2,000kg isn't just about replacement cost. It's about having the same grinder performance next year that you have today.

So Which One?

If you're grinding a few cups of filter coffee per week, uncoated stainless is fine.

If you're pulling espresso daily, you want DLC minimum.

If you're serious about longevity and performance, especially with light roasts or high-volume use, ta-C on a proper substrate is the only choice that makes sense.

We chose ta-C on tool steel because we're not building grinders designed to be replaced. We're building grinders designed to last.