| 摘要 |
<p>A core bit provided with a tube (2) having an opening (21) in an axial direction and a plurality of tips (3) fixed to the opening (21) of the tube (2). Each tip (3) contains an abrasive grain layer (31). The grain layer (31) contains diamond abrasive grains and a binder which binds the diamond abrasive grains together. The diamond abrasive grains contains 0.03 wt.% or less inclusion. The inclusion contains iron and nickel as its main components. The binder contains 0.1 wt.% or more but 2.0 wt.% or less graphite. The core bit takes a short time in drilling, that is, has a high cutting speed and a good sharpness, and is excellent in durability and long in service life. The core bit is suitable for drilling a hole in a concrete structure.</p> |
