| 摘要 |
A rock drill ( 1 ) for cutting rock comprising an elongated, helical shaft ( 2 ), which has, at one end, an insertion part ( 3 ) and, at the end opposite, a tool head ( 4 ) with cutters ( 5 ) made of hard material, wherein the helical shaft ( 2 ) is at least partially coated with a colored layer ( 7 a , 7 b) and the layer forms a lengthwise running wear indicator marking ( 8 ) inside the helical groove ( 8 ).
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