GESTEINSBOHRER

摘要

Drill (1) for drilling rock comprises an elongated spiral shaft (2) having at one end an insertion end (3) and at the opposite end a tool head (4) with cutting edges (5) made of hard material. The shaft is at least partly coated with a colored layer (7a, 7b) forming a wear marking (9) within and along a spiral groove (8). Preferred Features: Secondary spiral spines (10a, 10b) which are radially smaller than the spiral (6) are coated with the colored layer. The wear marking is formed by stripes.