Skills · skill
Sharpening an Edge
Metalwork · Beginner
- Difficulty
- Beginner
- Safety
- The edge is the hazard. Cut away from yourself when testing; keep fingers behind the edge on the stone.
- Done When
- It slices paper cleanly along its whole length, shaves arm hair, and shows no reflected line of light when looked at edge-on.
- Tools
- Combination water or oil stones (1000/6000), or a diamond plate; a strop with compound; a marker pen; good light.
- Category
- Metalwork
- Summary
- Bringing two ground faces of hardened steel to a clean intersection — the difference between a tool that cuts and one that tears.
Steps
Colour the bevel with marker; a few strokes on the coarse stone show whether you are holding the angle.
Raise a burr along the whole edge on the coarse stone — feel for it on the far side.
Flip and repeat until the burr moves to the first side.
Repeat on the fine stone with light pressure, alternating sides.
Strop away the burr on leather, edge trailing.
Test.
The Science
An edge is sharp when the two bevels meet in a line a fraction of a micron wide. Abrasive — aluminium oxide, silicon carbide, diamond — cuts the steel; coarse grits shape the bevel, fine grits reduce the scratch pattern until the edge is smooth enough to reflect no light. A burr forms as you reach the edge and must be removed, or it folds over on first use. Angle matters more than pressure: 15° per side for a kitchen knife, 25° for a chisel.
How It Fails
A rounded, dull edge from rocking the angle. A wire edge that felt sharp and folded on the first cut — the burr was not removed. Uneven bevels from more strokes on one side.
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