Knife Grinding: The Full Sequence from Primary Bevel to Final Edge

📅 Aug 03, 2026 👁 views

Grinding turns a hardened blank into a knife. It is the most labour-intensive stage in most cutlery factories, the stage most likely to be quietly degraded to hit a price, and the stage where the quality that a customer actually feels is created.

This article follows the grind from primary bevel to final edge and explains what each step contributes and how each can go wrong.

The sequence

Step	Removes	Abrasive	Purpose	Failure mode
Pre-grind or flatten	Scale, decarburised layer, distortion	Coarse wheel	Establishes flat datums	Leaving decarburised skin on the blade face
Profile grinding	Outline corrections	Coarse belt or wheel	Sets the outline and the spine line	Removing too much, changing blade height
Primary bevel	The bulk of the material to establish the taper	Coarse, commonly in the 40–80 grit range	Creates the grind face and the thickness behind the edge	Overheating; grinding past the intended thickness
Secondary bevel or edge bevel	Sets the actual cutting angle	Medium, commonly 120–400 grit	Defines the edge geometry	Wrong angle; inconsistency along the blade
Edge refinement	Reduces scratch depth at the apex	Fine, commonly 600–2000 grit	Removes the burr, forms a clean apex	Rounding the apex by over-polishing
Buffing or stropping	Final polish at the apex	Buff with compound	Removes the last burr remnants	Over-buffing produces a convex, weak apex
Finishing the faces and spine	Cosmetic passes	Per the finish specification	Surface appearance	Changing the finish by hand on some pieces only

Grind geometry — what each type means in production

Grind	Cross-section	Grinding difficulty	Thickness behind edge at a given angle	Character
Full flat	Flat faces from spine to edge, or nearly	Moderate — a large flat contact area	Low, excellent slicer	Best all-round cutting geometry
Sabre / flat with a shoulder	Flat upper face, distinct bevel at the edge	Easy — clear reference surfaces	Higher, robust	Strong, forgiving, common in European knives
Hollow	Concave faces from a large wheel	Moderate; the wheel must be dressed and true	Very low at the edge, thin behind it	Excellent slicer, fragile edge
Convex	Gently curved faces	Hard — no flat reference, requires skill or a jig	Variable; can be thin at the edge with mass above	Strong and good cutting, hard to make consistently
Scandi	Single flat bevel with no secondary edge bevel	Easy to control the angle, difficult to keep flat over a long blade	Very low at the shoulder	Tough and easy to sharpen in the field
Single bevel (Japanese)	Flat ground on one side, hollow or flat on the back	Difficult; the back must be flat and the bevel consistent	Very low	Precision slicing; requires skill and care

"Thickness behind the edge" is the parameter that determines cutting feel and it is distinct from the edge angle. A 15 degree edge on a 0.5 mm thick blank that has not been thinned will cut far worse than a 20 degree edge on a blade ground to 0.15 mm behind the edge. Buyers who specify only an angle and not a behind-edge thickness have specified half the geometry. See grinds explained and what makes a knife sharp.

Heat — the defect that cannot be seen

Grinding generates heat at the contact point. On a thin section near the edge, that heat can exceed the tempering temperature of the steel and soften it. The result is a blade that tested at the right hardness at the middle of the face and has a soft, easily dulled edge.

Heat damage	Temperature reached	Visible sign	Consequence
Temper draw	Above the tempering temperature, below the transformation range	Straw, brown or blue tint on the steel	Soft edge, poor edge retention
Re-hardening	Above the austenitising temperature locally	Bright blue or grey zone with a hard, untempered structure	Brittle, chipping edge
Grinding cracks	Localised rapid heating and cooling	Fine cracks, sometimes only visible after inspection or in use	Catastrophic failure potential
Grain growth	Extended high temperature	None visible	Reduced toughness throughout the affected zone

Control	How it works	What to specify
Coolant delivery	Cools the contact zone and flushes swarf	Coolant type, flow, nozzle position, and the requirement that it is maintained
Light passes	Reduces the heat generated per pass	Maximum depth of cut per pass in the process instruction
Wheel or belt condition	A glazed or loaded abrasive generates more heat	Dressing intervals; belt change schedule
Feed rate control	Slower feed reduces heat per unit time in a thin section	Stated feed rate, and a slower rate near the edge
Deliberate cooling pauses	Lets the section cool before further grinding	Included in the process instruction for thin and premium products
Hardness verification after grinding	Detects a soft edge before packing	Hardness measured at a defined distance behind the edge, per batch

If you specify one control and only one, specify hardness testing after grinding at a defined distance behind the edge. It is the only control that catches the defect rather than preventing it, and it is cheap. See verifying hardness.

Grinding in different production settings

Setting	Method	Consistency	Cost	Suitable for
Fully manual	Operator holds the blade against a belt or wheel	Operator-dependent	Lowest per hour, high variability	Low-cost production; craft work
Jig-assisted manual	Angle jig holds the blade	Good for the angle, still operator-dependent for pressure	Low	Most mid-market production
Semi-automatic	Powered fixture, operator loads	Good	Moderate	Volume production of a stable shape
CNC grinding	Programmed path, machine-controlled	Excellent	High capital, low marginal	Consistent geometry, complex grinds
Robotic grinding and polishing	Robot with force control	Very good with correct programming	High capital	High-volume consistent finishing
Hand grinding with stones	Craft method	Highly operator-dependent	Very high labour	Premium single-bevel and craft knives

The move from jig-assisted to semi-automatic or CNC is essentially a consistency investment. It shows up in a lower rejection rate and, more importantly, in a distribution of edge angles that is tight rather than wide. If you receive a test report with edge angle measurements, look at the spread, not the average. A tight average with a wide spread is a manual operation with variable pressure. See in-process quality control.

What to specify for the grind

Grind type, named and drawn in cross-section.
Edge angle in degrees per side, measured at defined points — typically heel, mid-blade and near the tip.
Thickness behind the edge at the same defined points.
Grind height, either as an absolute measurement or as a proportion of blade height.
Whether the grind is fully machine or partly hand finished.
Coolant and feed parameters, or a reference to the process instruction.
Hardness verification after grinding, with location and sample size.
Acceptance criteria for visual defects: grinding marks, dips, waves along the edge line.
Sharpness test method and pass criterion.

How grind quality shows up commercially

Grind quality	Customer perception	Business effect
Thin behind the edge, consistent angle	"This knife cuts"	Reviews, repeat purchase, word of mouth
Thick behind the edge, correct angle	"It's sharp but it wedges"	Returns, mediocre reviews
Variable angle along the blade	"Hard to keep sharp"	Blame on the customer's sharpening; lost repeat purchase
Soft edge from grinding heat	"Dulls quickly"	Warranty claims, brand damage
Visible grinding marks on a mirror finish	"Not as premium as it looked"	Markdowns, unsold stock

Grinding is where a knife programme is won or lost commercially, and it is the hardest stage to audit from a photograph. The controls that matter are a retained golden sample with measured geometry, an agreed hardness verification point, and an edge angle measurement at defined positions. Those three, taken together, are a more useful quality system than any certificate. See edge geometry testing and sharpness testing.