Achieving precise hole diameter
| Type | Accuracy | Ra (um) | Allowance |
|---|---|---|---|
| Solid HSS | H6-H7 | 0.4-0.8 | 0.1-0.2mm |
| Solid Carbide | H5-H7 | 0.2-0.6 | 0.08-0.15mm |
| Expansion | H6-H8 | 0.4-1.0 | 0.1-0.2mm |
Speed: 50-70% of drilling speed. Flutes: straight (thru), helical right (blind), helical left (interrupted).