In the past 100 years, both the domestic and overseas excavation industry employed only
hexagon and round
hollow rock drill
steels for rock drilling engineering. The nominal diameter series of inscribed circle for hexagon hollow rock drill steels include: H19, H22, H25, H28, H32,H35,H38, H45
mm and H48mm; whereas the nominal diameter series of inscribed circle for round hollow rock drill steel include: D32, D38, D45 and D51mm. This paper put forwards and demonstrates the hollow rock drill steels series of heptagon(code: Q), octagon (code: B) and enneagon(code: J) whose circumcircle diameters are uniform to those of Hexagon of same series, i.e.,,-19,22,25,28,32,35,38,45 and 48mm new type hollow rock drill steels. Especially the heptagon and enneagon series hollow rock drill steels with odd edges will possess much better anti-rupture and anti-bending capability than the hexagon and round hollow rock drill steels of same diameters which were employed before. Henceforth, the service life of the
integral drill steel and the
drill rod will be greatly improved.
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