A corner radius on an end mill replaces the sharp 90-degree corner with a small curve. Tiny radii strengthen the edge for roughing tough materials; larger radii cut intentional fillets into the part.
| Corner radius (in) | mm | Common use |
|---|---|---|
| 0.005 | 0.13 | Strengthen the edge for tough alloys |
| 0.010 | 0.25 | Light edge protection, semi-finish |
| 0.015 | 0.38 | Roughing in steel and stainless |
| 0.020 | 0.51 | General roughing durability |
| 0.030 | 0.76 | Heavy roughing, small fillets |
| 1/64 (0.0156) | 25.40 | Standard small fillet |
| 1/32 (0.0313) | 25.40 | Common fillet radius |
| 1/16 (0.0625) | 25.40 | Larger fillet or blend |
Common stock radii; many sizes are available as specials. A corner-radius (bull nose) tool lasts far longer than a square end mill in hard, interrupted cuts.
See the End Mill Selection Chart.