Glossary & Reference
Sintering and coating aren't the last steps in making a modern insert. A round of post-treatment — edge honing and, on coated grades, wet blasting or brushing — is what turns a technically sharp edge into one that actually survives the cut.
After grinding, a carbide edge can be ground down to a genuinely sharp, almost feather-thin apex. That sounds like an advantage, but at the microscopic level a razor-sharp ground edge is mechanically fragile — there's very little material backing it up, so it's prone to chipping out under the first few impacts of a cut, especially in interrupted or roughing work. On the coating side, the coating process itself — whether CVD or PVD — leaves behind small imperfections: coating droplets, uneven grain buildup, and residual stress baked into the layer. Post-treatment addresses both problems after the insert is otherwise finished.
Edge honing applies a small, controlled micro-radius (or a chamfer, or a combination of both) to the as-ground edge instead of leaving it needle-sharp. Major manufacturers such as Sandvik Coromant and Kennametal typically finish edges with a hone in the roughly 5–10 micron range for general-purpose grades, with heavier hones or chamfers used for interrupted cuts and tougher, more impact-resistant applications. The trade-off is deliberate: a honed edge gives up a small amount of sharpness in exchange for a meaningful, well-documented improvement in resistance to chipping and a longer, more predictable tool life.
On coated inserts, a secondary treatment is commonly applied after the coating cycle — typically wet blasting (a fine abrasive-and-water slurry directed at the surface) or mechanical brushing. Both processes relieve residual stress left in the coating, smooth out coating-surface imperfections like droplets and rough grain boundaries, and lower the surface friction of the finished edge. A smoother, lower-friction coating surface reduces the tendency for chips to weld onto the tool, which helps control built-up edge and keeps the cutting action more consistent over the life of the insert.
These two treatments — edge honing and post-coating wet blasting/brushing — are the well-documented, widely used post-treatments across the major tooling brands. Exotic secondary treatments are sometimes marketed by individual manufacturers, but edge preparation and surface finishing after coating are the two you'll find consistently described in tooling-manufacturer technical literature.