Version:
Ground from solid and relief ground, spiral fluted.
Centre drill with radius form R:
- The radius curve eliminates the sharp transition from drill point to countersink angle that is present on form A, so the risk of fracture is reduced.
- In the event of angular misalignment of the lathe centre, the ring bearing face avoids the component running only on the external or internal edge of the bearing face. Even if the lathe centres are not in line, good support is provided.