Knife Grinds Explained: Flat, Hollow, Convex, Scandi and Chisel
Two knives at the same hardness from the same steel, ground differently, cut completely differently. The grind — the geometry of the blade's cross section — determines how the knife enters food, how it releases, how strong the edge is and how it sharpens. It is the most under-specified aspect of most knife programmes.
This article compares the principal grind types and what each is for.
The five grinds
| Grind | Cross section | Strength | Cutting feel | Typical use |
|---|---|---|---|---|
| Flat | Straight taper from spine to edge | Good | Clean, predictable | General purpose; the most common production grind |
| Hollow | Concave, ground on a wheel | Lowest | Very keen initially, can wedge less in some foods | Traditional Western razors and some kitchen knives |
| Convex (hamaguri) | Gentle outward curve | Highest | Smooth, more resistance in dense food | Heavy-duty, chopping, Japanese axes and some gyuto |
| Scandi | Single flat bevel from spine to apex | Moderate | Excellent in wood, poor in food release | Bushcraft and carving; unusual on kitchen knives |
| Chisel (single bevel) | Flat on one face, bevel on the other | Moderate | Extremely accurate slicing; steers | Japanese traditional single-bevel knives |
The numbers that matter more than the name
The grind name is a shorthand. What actually determines behaviour is three measurements:
| Measurement | Effect if increased | Effect if decreased |
|---|---|---|
| Bevel angle (included angle at the edge) | Stronger edge, worse cutting, more wedging | Keen cutting, weaker edge, more chipping risk |
| Thickness behind the edge | Blade wedges in food, feels blunt even when sharp | Cuts freely, edge more fragile |
| Blade thickness at the spine | Heavier, stiffer, more splitting than slicing | Lighter and slicier, less stiff |
Thickness behind the edge is the parameter most often wrong and least often specified. A knife can be sharpened to a perfect apex and still feel dull because 0.5 mm of steel sits immediately behind it and wedges the blade in the food before the edge can do its work. This is the difference between a knife that is "sharp" and one that cuts well.
Comparing grinds on the same steel
| Property | Flat | Hollow | Convex |
|---|---|---|---|
| Initial keenness | Good | Highest | Good |
| Edge support | Moderate | Low | High |
| Food release | Moderate | Moderate | Poorer — more surface contact |
| Wedging in dense food | Moderate | Lower | Higher |
| Ease of sharpening by hand | Easy | Difficult to maintain | Hardest to maintain freehand |
| Manufacturing difficulty | Moderate | Requires large contact wheels | Requires skill or CNC |
| Resistance to chipping | Moderate | Lowest | Highest |
Why manufacturing finds this hard
- Hollow grinds need big wheels. The radius of the wheel sets the concavity, and the grinding forces are high. Maintaining the wheel profile across a production run is a real discipline.
- Convex grinds are hard to automate. A concave or flat grind can be produced by a machine following a path. A convex grind requires either a slack belt, a controlled-radius contact wheel and operator skill, or a CNC grinder capable of the profile.
- Thin-behind-the-edge is slow. Removing steel from behind the edge is time-consuming, and it is the first thing that gets reduced when a factory is under schedule pressure, because it is invisible in a visual inspection and measurable only with a caliper. This is a cost-reduction drift worth controlling — see grinding process.
- Grinding shape changes with wheel wear. Without scheduled wheel dressing and periodic cross-section checks, geometry drifts across a batch.
What to specify
| Item | How to state it |
|---|---|
| Grind type | Name plus a cross-section drawing |
| Bevel angle | Included angle in degrees, with tolerance |
| Thickness behind the edge | Measured at a stated distance from the apex, with tolerance |
| Blade thickness at spine | With tolerance |
| Finishing of the bevel | Grit or finish standard, referenced to a sample |
| Reference sample | A gold sample for cross-section comparison — see sampling |
The cross-section drawing is the single most useful document in a knife specification, and the least commonly provided. A profile drawing shows the outline; a cross section shows how it will cut. Where a programme has recurring complaints that a knife "feels blunt", the cross section is where to look.
FAQ
Which grind is sharpest?
All of them can be sharpened to an equivalent apex. Hollow grinds feel sharpest off the stone because the blade behind the edge is thinner, but a hollow grind has the least support and dulls or chips fastest in rough use.
Is a thin blade always better for cutting?
For slicing soft food, generally yes. For chopping, root vegetables and anything that requires lateral force, thin blades deflect and their edges are more exposed to damage. The right thickness depends on the intended task — see knife types.
Can a grind be changed after purchase?
Yes, by regrinding, and this is what thinning is. It is significant work and changes the blade permanently. Retail customers should not be encouraged to attempt it.
Does a Damascus pattern affect the grind?
It can constrain it. A clad blade with a thin core limits how much can be ground away before the core is exposed too far or lost — see clad construction.
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