| 摘要 |
A circular cutting head assembly and centering drill of the type used, for example, in cutting holes in structural members such as I-beam webs, and flanges. The circular drill is characterized by a cylindrical body portion, supporting an inner centering drill plug. The centering drill plug is axially depressable as a centering hole is cut, so as to be pushed out of a mode of cutting registry with the outer cutting head and into a mode of non-registry which permits axial flow of lubricating oil through the body portion and onto the surface being cut within the periphery of the cutting teeth of the outer cutting head.
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