| 摘要 |
A rotary bit for drilling concrete and reinforced concrete having a hollow drill stem with a transversely disposed drilling face at its outer end, the face having annularly disposed sawtooth surfaces including abrupt step portions alternating with trailing portions extending from the apex of a step to the root of the succeeding step, the trailing portions having diamond chips thereon and comprising crushing and grinding surfaces for the cuttings, and being sloped radially outwardly and axially upwardly to displace particles toward the outer periphery of the bit, and the bit having particle escape channels up its side surface adjacent the leading edges of the step portions which have hardened cutter inserts.
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