Drill

A drill, comprising:

• a stem (8);
• and
• a one-piece drilling head (10;
• 20;
• 30) formed of a hard material and provided, at a first end (5) thereof, with at least one main bit having a tip (4) and at least one cutting structure (3) integral to the one-piece drilling head (10;
• 20;
• 30), and at a second end (6), located opposite the first end (5), with a bottom surface (7) for mounting the drilling head (10;
• 20;
• 30) on the stem (8), and having a plurality of axially extending through-grooves (11;
• 21;
• 31) for removing drillings produced during a drilling process and having a cross-section which increases, at least regionwise, in a direction toward the bottom surface (7) of the drilling head (10;
• 20;
• 30);
• wherein a cross-section of each of the through-grooves (11;
• 21;
• 31) has a respective tangential transition edge (12;
• 22;
• 32) spaced from the bottom surface (7) by a respective distance (a;
• b;
• d) corresponding to about from 10% to 40% of a distance (D) from the tip (4) to the bottom surface (7).