Assertion: drill bit | /r/HasProperty | classified in three groups
Facets:
value: for special purposes
type: PURPOSE
value: according to purpose
type: CAUSE
Source sentences:
text: Drill bits are classified in three groups according to purpose or use: for continuous drilling (crushing of rock over the entire face of the borehole), for core drilling (crushing of rock in a ring around the wall of a borehole, retaining the central part of the core), and for special purposes (drilling out cement in a pipe string, reaming a borehole, and so on).