Hamaguri Style Sharpening

Convex Edge / Japanese Edge / Hamaguri Sharpening Theory

A high-level overview of Japanese-style convex sharpening theory (hamaguri), with practical steps you can apply immediately.

In this module, you will learn:

• The geometry you’re protecting: convex exterior, inside hollow + ride line (“seal”), and the apex
• Why the sequence works: stone first (datum), flat hone next (controlled burr), stone last (de-burr & re-seal)
• Practical grits & media ranges for inside waterstones and flat-hone films
• A repeatable SOP: diagnostics → inside stone → flat-hone → inside de-burr → finish → test
• Key checks & tests: burr continuity, apex light test, tissue/foil/hair tests
• The three edge killers (pressure, heat, passes) and how to avoid them
• Steel-specific burr behavior (VG10/ATS-314 vs 440C)
• Common failure modes (widened ride line, wire edge, no tip burr, contamination) and fixes
• Contour control (following factory radius), damage triage, finishing choices, and a quick checklist