DOWN-THE-HOLE ROCK DRILL

摘要

The present down-the-hole rock drill is characterized in a com- bination of features where the first feature is that the lower portion (18a; 18'a) of the shank (18; 18') of the drill bit (19)/guide device (19') is given a cross-sectional shape that is a multi-lobed figure that is continuously non-concave and the second feature is that the upper portion (18b; 18'b) of the shank (18; 18') of the drill bit (19)/guide device (19') is provided with a shoulder means (21; 21') on said sec- ond portion (18b; 18'b) of the shank (18; 18').