| 摘要 |
Disclosed according to the invention is a center vacuum roof drill bit. The roof drill bit has a body having an axis of rotation, a seat transverse to the axis of rotation, a periphery and a forward working end. The roof drill bit has at least one flat-like insert positioned on the seat. There is also means for releasably clamping the insert, the means clamping the insert near the periphery only of the body. In other embodiments of the roof drill bit, there is a second flat-like insert and, additionally, provisions are made for self centering the insert or inserts.
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