Rotary drill bit having an insert with leading and trailing relief portions

摘要

A roof drill bit having a tool body with a cutting insert brazed thereto. The cutting insert has opposite leading and trailing face portions joined by a side surface which has a leading side relief portion adjacent the leading face portion and a trailing side relief portion adjacent the trailing face portion. The trailing side relief portion, which extends from the leading face portion a distance equal to between about one-third to two-thirds the thickness of the insert, has a greater relief angle that the leading side relief portion, which extends from the trailing face portion a distance equal to between about one-third to about two-thirds the thickness of the insert.