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US07628232B2 Rotary-percussion drill with a four-start helical shaft 有权
旋转冲击钻具有四开式螺旋轴

Rotary-percussion drill with a four-start helical shaft
摘要:
A rotary-percussion drill includes a four-start helical shaft (3) having a fourfold rotationally and mirror-symmetrical helix cross-section, with radially projecting convexly formed helical webs (4) extending from a concave groove bottom (5) up to the envelope circle (6) and having an undercut (7) with respect to a web width (S).
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