PURPOSE: To facilitate the discharge of a chip, to improve cutting property and to continue a high cutting property at all times until a diamond cutting blade is lost, by providing chips discharging grooves alternately at both parts of the inner and outer faces of a diamond cutting blade.
CONSTITUTION: A chips discharging groove 3 in the dimension of more than 1/2 of the thickness (t) in the radial direction is provided more than one alternately on the inner and outer both faces on a diamond cutting blade 2. The discharging of a chip is thus facilitated by providing the chips discharging groove 3 and the punching speed of a diamond core drill is continued at the value of more than 80% of the initial punching speed at all times until this cutting blade 2 is lost.
ABE TAKAO
ODAKA MAMORU
TAKEISHI KAZUSANE
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