Abstract: A method of a blast process for a junction part between a large-diameter main bore tubularly drilled through an article and a small-diameter branch bore branching off at an angle from the main bore inside the article. A pillar-shaped rod is inserted from a first open end of the main bore to a point close to the junction part before a leading end of the rod blocks the branch bore. A wet slurry made of a mixture of abrasives and water is jetted from a second open end of the main bore into the main bore by use of a squirt gun. The blast of wet slurry is collided with the leading end of the rod and redirected toward the branch bore to drive the abrasives against the junction part located inside the article for removal of burrs therefrom the junction part.

Abstract: A method of a blast process for a junction part between a large-diameter main bore tubularly drilled through an article and a small-diameter branch bore branching off at an angle from the main bore inside the article. A pillar-shaped rod is inserted from a first open end of the main bore to a point close to the junction part before a leading end of the rod blocks the branch bore. A wet slurry made of a mixture of abrasives and water is jetted from a second open end of the main bore into the main bore by use of a squirt gun. The blast of wet slurry is collided with the leading end of the rod and redirected toward the branch bore to drive the abrasives against the junction part located inside the article for removal of burrs therefrom the junction part.