发明授权
US4527638A Mine tool roof bit insert and a method of drilling therewith 失效
矿山工具车顶钻头刀片及其钻孔方法

Mine tool roof bit insert and a method of drilling therewith
摘要:
A mine tool roof bit insert geometry of a 30.degree. top relief angle between the top cutting edge and the top trailing edge and a radius of curvature of 1/16 inch at the corners improves the maximum wear and penetration rate when drilling into sandstone and a method therewith is described.
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